From d209839fb90756da34d1b3daf5c10d17ae75c5a3 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Mon, 16 Jun 2025 19:31:02 +0000
Subject: [PATCH 01/17] Converted callbacks to std::function and added error
 checking

---
 src/CANController.cpp |  2 +-
 src/CANController.h   |  6 ++++--
 src/ESP32SJA1000.cpp  | 40 +++++++++++++++++++++++++++++-----------
 src/ESP32SJA1000.h    |  2 +-
 4 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/src/CANController.cpp b/src/CANController.cpp
index 0890eec..a1d9fdb 100644
--- a/src/CANController.cpp
+++ b/src/CANController.cpp
@@ -180,7 +180,7 @@ void CANControllerClass::flush()
 {
 }
 
-void CANControllerClass::onReceive(void(*callback)(int))
+void CANControllerClass::onReceive(TCallback callback)
 {
   _onReceive = callback;
 }
diff --git a/src/CANController.h b/src/CANController.h
index cdaeb94..afd4ea9 100644
--- a/src/CANController.h
+++ b/src/CANController.h
@@ -6,6 +6,8 @@
 
 #include <Arduino.h>
 
+typedef std::function<void (int packetSize)> TCallback;
+
 class CANControllerClass : public Stream {
 
 public:
@@ -32,7 +34,7 @@ class CANControllerClass : public Stream {
   virtual int peek();
   virtual void flush();
 
-  virtual void onReceive(void(*callback)(int));
+  void onReceive(TCallback callback);
 
   virtual int filter(int id) { return filter(id, 0x7ff); }
   virtual int filter(int id, int mask);
@@ -49,7 +51,7 @@ class CANControllerClass : public Stream {
   virtual ~CANControllerClass();
 
 protected:
-  void (*_onReceive)(int);
+  TCallback _onReceive;
 
   bool _packetBegun;
   long _txId;
diff --git a/src/ESP32SJA1000.cpp b/src/ESP32SJA1000.cpp
index 309e030..9ef9378 100644
--- a/src/ESP32SJA1000.cpp
+++ b/src/ESP32SJA1000.cpp
@@ -33,6 +33,10 @@
 
 #define REG_CDR                    0x1F
 
+#define IR_EI 0x02 // Error Interrupt flag
+
+#define SR_TCS 0x08  // Transmit Complete Status
+#define SR_TBS 0x04  // Transmit Buffer Status (free)
 
 ESP32SJA1000Class::ESP32SJA1000Class() :
   CANControllerClass(),
@@ -67,7 +71,9 @@ int ESP32SJA1000Class::begin(long baudRate)
   gpio_pad_select_gpio(_txPin);
 
   modifyRegister(REG_CDR, 0x80, 0x80); // pelican mode
-  modifyRegister(REG_BTR0, 0xc0, 0x40); // SJW = 1
+  modifyRegister(REG_BTR0, 0xc0, 0x40); // SJW = 2
+  // modifyRegister(REG_BTR0, 0xc0, 0x80); // SJW = 3
+  // modifyRegister(REG_BTR0, 0xc0, 0x00); // SJW = 1
   modifyRegister(REG_BTR1, 0x70, 0x10); // TSEG2 = 1
 
   switch (baudRate) {
@@ -169,7 +175,7 @@ int ESP32SJA1000Class::endPacket()
   }
 
   // wait for TX buffer to free
-  while ((readRegister(REG_SR) & 0x04) != 0x04) {
+  while (!(readRegister(REG_SR) & SR_TBS)) {
     yield();
   }
 
@@ -199,19 +205,31 @@ int ESP32SJA1000Class::endPacket()
     // self reception request
     modifyRegister(REG_CMR, 0x1f, 0x10);
   } else {
+	// Check one more time to be sure the tx buffer is free
+	while (!(readRegister(REG_SR) & SR_TBS)) {
+	  yield(); // Allow background tasks to happen
+	}
+
+	// Wait for bus to be recessive before transmitting
+	while (readRegister(REG_SR) & 0x10) { // SR_RS = Receive Status = 1 means dominant
+	  delayMicroseconds(10);
+	}
+
     // transmit request
     modifyRegister(REG_CMR, 0x1f, 0x01);
   }
 
-  // wait for TX complete
-  while ((readRegister(REG_SR) & 0x08) != 0x08) {
-    if (readRegister(REG_ECC) == 0xd9) {
-      modifyRegister(REG_CMR, 0x1f, 0x02); // error, abort
-      return 0;
-    }
-    yield();
+  // wait for TX complete and buffer to be free, then check for errors
+  while (!((readRegister(REG_SR) & (SR_TCS | SR_TBS)) == (SR_TCS | SR_TBS))) { 
+	  if (readRegister(REG_IR) & IR_EI) { // Error interrupt must be set to check for an error code
+		  if (readRegister(REG_ECC) != 0x00) { // Check error code
+			  modifyRegister(REG_CMR, 0x1F, 0x02); // Abort transmission
+			  return 0;
+		  }
+	  }
+	  yield(); // Allow multitasking
   }
-
+  
   return 1;
 }
 
@@ -258,7 +276,7 @@ int ESP32SJA1000Class::parsePacket()
   return _rxDlc;
 }
 
-void ESP32SJA1000Class::onReceive(void(*callback)(int))
+void ESP32SJA1000Class::onReceive(TCallback callback)
 {
   CANControllerClass::onReceive(callback);
 
diff --git a/src/ESP32SJA1000.h b/src/ESP32SJA1000.h
index b83cddc..696eabf 100644
--- a/src/ESP32SJA1000.h
+++ b/src/ESP32SJA1000.h
@@ -24,7 +24,7 @@ class ESP32SJA1000Class : public CANControllerClass {
 
   virtual int parsePacket();
 
-  virtual void onReceive(void(*callback)(int));
+  virtual void onReceive(TCallback callback);
 
   using CANControllerClass::filter;
   virtual int filter(int id, int mask);

From 56c87bfed445126c5e12ceab41ce4d6871883dd9 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Tue, 17 Jun 2025 22:30:46 +0000
Subject: [PATCH 02/17] Added error handling

---
 src/CANController.cpp | 6 ++++++
 src/CANController.h   | 3 +++
 src/ESP32SJA1000.cpp  | 7 ++++---
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/CANController.cpp b/src/CANController.cpp
index a1d9fdb..18b643b 100644
--- a/src/CANController.cpp
+++ b/src/CANController.cpp
@@ -5,6 +5,7 @@
 
 CANControllerClass::CANControllerClass() :
   _onReceive(NULL),
+  _onError(NULL),
 
   _packetBegun(false),
   _txId(-1),
@@ -185,6 +186,11 @@ void CANControllerClass::onReceive(TCallback callback)
   _onReceive = callback;
 }
 
+void CANControllerClass::onError(TErrorCallback callback)
+{
+  _onError = callback;
+}
+
 int CANControllerClass::filter(int /*id*/, int /*mask*/)
 {
   return 0;
diff --git a/src/CANController.h b/src/CANController.h
index afd4ea9..6e7cbc4 100644
--- a/src/CANController.h
+++ b/src/CANController.h
@@ -7,6 +7,7 @@
 #include <Arduino.h>
 
 typedef std::function<void (int packetSize)> TCallback;
+typedef std::function<void (int eir, int ecc)> TErrorCallback;
 
 class CANControllerClass : public Stream {
 
@@ -35,6 +36,7 @@ class CANControllerClass : public Stream {
   virtual void flush();
 
   void onReceive(TCallback callback);
+  void onError(TErrorCallback callback);
 
   virtual int filter(int id) { return filter(id, 0x7ff); }
   virtual int filter(int id, int mask);
@@ -52,6 +54,7 @@ class CANControllerClass : public Stream {
 
 protected:
   TCallback _onReceive;
+  TErrorCallback _onError;
 
   bool _packetBegun;
   long _txId;
diff --git a/src/ESP32SJA1000.cpp b/src/ESP32SJA1000.cpp
index 9ef9378..e70dd40 100644
--- a/src/ESP32SJA1000.cpp
+++ b/src/ESP32SJA1000.cpp
@@ -394,12 +394,13 @@ void ESP32SJA1000Class::handleInterrupt()
 {
   uint8_t ir = readRegister(REG_IR);
 
-  if (ir & 0x01) {
+  if (ir & IR_EI) { // Error interrupt must be set to check for an error code
+    _onError(readRegister(REG_EIR), readRegister(REG_ECC));
+  } else if (ir & 0x01) {
     // received packet, parse and call callback
     parsePacket();
-
     _onReceive(available());
-  }
+  } 
 }
 
 uint8_t ESP32SJA1000Class::readRegister(uint8_t address)

From 36ca4d94eca82e34f984ddd4e7adfca2741b5d86 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Tue, 17 Jun 2025 22:32:02 +0000
Subject: [PATCH 03/17] Exposed readRegister

---
 src/ESP32SJA1000.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ESP32SJA1000.h b/src/ESP32SJA1000.h
index 696eabf..b432dee 100644
--- a/src/ESP32SJA1000.h
+++ b/src/ESP32SJA1000.h
@@ -39,13 +39,13 @@ class ESP32SJA1000Class : public CANControllerClass {
   void setPins(int rx, int tx);
 
   void dumpRegisters(Stream& out);
+  uint8_t readRegister(uint8_t address);
 
 private:
   void reset();
 
   void handleInterrupt();
 
-  uint8_t readRegister(uint8_t address);
   void modifyRegister(uint8_t address, uint8_t mask, uint8_t value);
   void writeRegister(uint8_t address, uint8_t value);
 

From ccfeb5bfefea8826f093f24587b84ea0b2e09873 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Tue, 17 Jun 2025 22:33:08 +0000
Subject: [PATCH 04/17] REG_EIR definition for error handling

---
 src/ESP32SJA1000.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/ESP32SJA1000.cpp b/src/ESP32SJA1000.cpp
index e70dd40..81e0560 100644
--- a/src/ESP32SJA1000.cpp
+++ b/src/ESP32SJA1000.cpp
@@ -31,6 +31,7 @@
 #define REG_ACRn(n)                (0x10 + n)
 #define REG_AMRn(n)                (0x14 + n)
 
+#define REG_EIR                    0x1C
 #define REG_CDR                    0x1F
 
 #define IR_EI 0x02 // Error Interrupt flag

From 71886f940465b5dc6321ae46c0a585ddcf8949c0 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Sat, 21 Jun 2025 01:34:05 +0000
Subject: [PATCH 05/17] Timing and processing tweaks

---
 src/ESP32SJA1000.cpp | 215 +++++++++++++++++++++++++++----------------
 src/ESP32SJA1000.h   |  11 +++
 2 files changed, 145 insertions(+), 81 deletions(-)

diff --git a/src/ESP32SJA1000.cpp b/src/ESP32SJA1000.cpp
index 81e0560..a51c091 100644
--- a/src/ESP32SJA1000.cpp
+++ b/src/ESP32SJA1000.cpp
@@ -7,6 +7,11 @@
 #include "soc/dport_reg.h"
 #include "driver/gpio.h"
 
+// These are to read the APB clock speed
+#include <soc/rtc_cntl_reg.h>
+#include <soc/soc.h>
+#include <esp32/rom/rtc.h>
+
 #include "ESP32SJA1000.h"
 
 #define REG_BASE                   0x3ff6b000
@@ -72,75 +77,88 @@ int ESP32SJA1000Class::begin(long baudRate)
   gpio_pad_select_gpio(_txPin);
 
   modifyRegister(REG_CDR, 0x80, 0x80); // pelican mode
-  modifyRegister(REG_BTR0, 0xc0, 0x40); // SJW = 2
-  // modifyRegister(REG_BTR0, 0xc0, 0x80); // SJW = 3
-  // modifyRegister(REG_BTR0, 0xc0, 0x00); // SJW = 1
-  modifyRegister(REG_BTR1, 0x70, 0x10); // TSEG2 = 1
 
+  // Masks:
+  // 0xc0: bits 6-7
+  // 0x3f: bits 0-5
+  //
+  // 0x80: bit 7
+  // 0x70: bits 4-6
+  // 0x0f: bits 0-3
+  //
+  // Validate with python:
+  // format(ord(chr(0xff & ~0x07 | 0x40)), 'b').zfill(8)
+
+  // Final SJW, BRP, TSEG1, and TSEG2 values are regval + 1
+  uint8_t sjw, brp, ts, tseg1, tseg2;
+  
   switch (baudRate) {
-    case (long)1000E3:
-      modifyRegister(REG_BTR1, 0x0f, 0x04);
-      modifyRegister(REG_BTR0, 0x3f, 4);
-      break;
-
     case (long)500E3:
-      modifyRegister(REG_BTR1, 0x0f, 0x0c);
-      modifyRegister(REG_BTR0, 0x3f, 4);
-      break;
-
-    case (long)250E3:
-      modifyRegister(REG_BTR1, 0x0f, 0x0c);
-      modifyRegister(REG_BTR0, 0x3f, 9);
-      break;
-
-    case (long)200E3:
-      modifyRegister(REG_BTR1, 0x0f, 0x0c);
-      modifyRegister(REG_BTR0, 0x3f, 12);
-      break;
-
-    case (long)125E3:
-      modifyRegister(REG_BTR1, 0x0f, 0x0c);
-      modifyRegister(REG_BTR0, 0x3f, 19);
+      // Target config is 500kbps, 75% sample point, triple sampling disabled
+      // ESP32 has an 80 Mhz APB clock (79998976 hz to be exact), 
+      // 80E6 / 500E3 = 160
+      // So theoretically, (BRP +1) * (1 + TSEG1+1 + TSEG2+1) must equal 160
+	  // The TWAI library 500k settings are brp=8, tseg_1=15, tseg_2=4, sjw=3, triple_sampling=false
+      // Which is 8 * (1 + 15 + 4) = 160
+      // But that doesn't seem to work at all 
+      // The ESP32-WROOM-32E datasheet says the crystal on this board is 40 Mhz 
+      // The TJA1000 datasheet says the clock is 24 Mhz
+	  // The clock divider is set to 0x00
+	  // The TJA1000 datasheet says CLKDIV 0x00 = 2 and 0x01 = 1
+	  // So let's do some experiments
+
+	  // 20 Mhz = 20E6/500E3 = 40 = 2x20; brp=2; 20x.75=15 (75% sample point); tseg1=15; 20-15=5; tseg2=5;
+	  // Acks first scanner packet, sends response, scaner acks, triggers CAN error on next scanner tx bit
+	  sjw = 2; ts = 0; brp = 2, tseg1 = 15, tseg2 = 5;
+	  
+	  // Same: sjw = 2; ts = 0; brp = 2, tseg1 = 14, tseg2 = 6;
+	  // Nope: sjw = 2; ts = 0; brp = 2, tseg1 = 15, tseg2 = 6;
+	  // sjw = 2; ts = 0; brp = 2, tseg1 = 16, tseg2 = 4;
+
+	  // 24 Mhz = 24E6/500E3 = 48 = 3x16; brp=3; 16x.75=12, tseg1=12; 16-12=4; tseg2=4;
+	  // Triggers error on first scanner packet CRC
+	  // sjw = 3; ts = 0; brp = 3, tseg1 = 12, tseg2 = 4;
+	  
+	  // 12 Mhz = 12E6/500E3 = 24 = 1x24; brp=1; 24*.75=18; tseg1=18; 24-18=6; tseg2=6; 
+      // Triggers CAN error after first scanner tx bit
+	  // sjw = 3; ts = 0; brp = 1, tseg1 = 18, tseg2 = 6;
+	  
+	  // 40 Mhz = 40E6/500E3 = 80 = 4x20; brp=4; 20x.75=15 (75% sample point); tseg1=15; 20-15=5; tseg2=5;
+	  // Triggers error after first scanner tx data bit
+	  // sjw = 3; ts = 0; brp = 4, tseg1 = 15, tseg2 = 5;
+
+	  // 80 Mhz = 80E6/500E3 = 160 = 8x20; brp=8; 20x.75=15; tseg1=15; 20-15=5; tseg2=5;
+	  // Triggers error after first scanner tx data bit
+	  // sjw = 3; ts = 0; brp = 8, tseg1 = 15, tseg2 = 5;
+
+      modifyRegister(REG_BTR0, 0xc0, sjw -1 << 6);   // SJW (bits 6-7) -1 because final value is regval+1
+      modifyRegister(REG_BTR0, 0x3f, brp -1);        // BRP (bits 0-5) -1 because final value is regval+1
+      modifyRegister(REG_BTR1, 0x80, ts << 7);       // Triple Sampling (bit 7)
+      modifyRegister(REG_BTR1, 0x70, tseg2 -1 << 4); // TSEG2 (bits 4-6) -1 because final value is regval+1
+      modifyRegister(REG_BTR1, 0x0f, tseg1 -2);      // TSEG1 (bits 0-3) -2 to account for regval+1 + SYNC bit
       break;
 
-    case (long)100E3:
-      modifyRegister(REG_BTR1, 0x0f, 0x0c);
-      modifyRegister(REG_BTR0, 0x3f, 24);
-      break;
-
-    case (long)80E3:
-      modifyRegister(REG_BTR1, 0x0f, 0x0c);
-      modifyRegister(REG_BTR0, 0x3f, 30);
-      break;
-
-    case (long)50E3:
-      modifyRegister(REG_BTR1, 0x0f, 0x0c);
-      modifyRegister(REG_BTR0, 0x3f, 49);
-      break;
-
-/*
-   Due to limitations in ESP32 hardware and/or RTOS software, baudrate can't be lower than 50kbps.
-   See https://esp32.com/viewtopic.php?t=2142
-*/
     default:
       return 0;
       break;
   }
 
-  modifyRegister(REG_BTR1, 0x80, 0x80); // SAM = 1
   writeRegister(REG_IER, 0xff); // enable all interrupts
 
-  // set filter to allow anything
+  // set filters to allow anything
   writeRegister(REG_ACRn(0), 0x00);
   writeRegister(REG_ACRn(1), 0x00);
   writeRegister(REG_ACRn(2), 0x00);
   writeRegister(REG_ACRn(3), 0x00);
+
   writeRegister(REG_AMRn(0), 0xff);
   writeRegister(REG_AMRn(1), 0xff);
   writeRegister(REG_AMRn(2), 0xff);
   writeRegister(REG_AMRn(3), 0xff);
 
-  modifyRegister(REG_OCR, 0x03, 0x02); // normal output mode
+  // normal output mode
+  modifyRegister(REG_OCR, 0x03, 0x02); 
+  
   // reset error counters
   writeRegister(REG_TXERR, 0x00);
   writeRegister(REG_RXERR, 0x00);
@@ -149,8 +167,12 @@ int ESP32SJA1000Class::begin(long baudRate)
   readRegister(REG_ECC);
   readRegister(REG_IR);
 
-  // normal mode
-  modifyRegister(REG_MOD, 0x08, 0x08);
+  // 0x17 = 0b00010111 → mask for:
+  // Bit 0: RM (Reset Mode)
+  // Bit 1: LOM (Listen Only Mode)
+  // Bit 2: STM (Self-Test Mode)
+  // Bit 4: AFM (Acceptance Filter Mode)
+  // Value 0x00 sets them all to 0x00
   modifyRegister(REG_MOD, 0x17, 0x00);
 
   return 1;
@@ -169,16 +191,33 @@ void ESP32SJA1000Class::end()
   CANControllerClass::end();
 }
 
+bool ESP32SJA1000Class::isTxComplete() {
+    return readRegister(REG_SR) & SR_TCS;
+}
+
+bool ESP32SJA1000Class::isTxBufferFree() {
+    return readRegister(REG_SR) & SR_TBS;
+}
+
+bool ESP32SJA1000Class::isBusRecessive() {
+    return (readRegister(REG_SR) & (1 << 4)) != 0;  // Bit 4 is SR_RX
+}
+
+bool ESP32SJA1000Class::isReadyToTransmit() {
+	return isTxBufferFree() && isBusRecessive();
+}
+
 int ESP32SJA1000Class::endPacket()
 {
   if (!CANControllerClass::endPacket()) {
     return 0;
   }
 
-  // wait for TX buffer to free
-  while (!(readRegister(REG_SR) & SR_TBS)) {
-    yield();
-  }
+  // while (_transmitting == true) {
+	// yield();
+  // }
+
+  _transmitting = true;
 
   int dataReg;
 
@@ -206,31 +245,20 @@ int ESP32SJA1000Class::endPacket()
     // self reception request
     modifyRegister(REG_CMR, 0x1f, 0x10);
   } else {
-	// Check one more time to be sure the tx buffer is free
-	while (!(readRegister(REG_SR) & SR_TBS)) {
-	  yield(); // Allow background tasks to happen
-	}
-
-	// Wait for bus to be recessive before transmitting
-	while (readRegister(REG_SR) & 0x10) { // SR_RS = Receive Status = 1 means dominant
-	  delayMicroseconds(10);
-	}
+    while (!isReadyToTransmit()) {
+      // yield(); // Allow background tasks to happen
+    }
 
     // transmit request
     modifyRegister(REG_CMR, 0x1f, 0x01);
   }
 
-  // wait for TX complete and buffer to be free, then check for errors
-  while (!((readRegister(REG_SR) & (SR_TCS | SR_TBS)) == (SR_TCS | SR_TBS))) { 
-	  if (readRegister(REG_IR) & IR_EI) { // Error interrupt must be set to check for an error code
-		  if (readRegister(REG_ECC) != 0x00) { // Check error code
-			  modifyRegister(REG_CMR, 0x1F, 0x02); // Abort transmission
-			  return 0;
-		  }
-	  }
-	  yield(); // Allow multitasking
+  // wait for TX complete, then return
+  while (!isTxComplete()) {
+	  // yield();
   }
   
+  _transmitting = true;
   return 1;
 }
 
@@ -393,15 +421,25 @@ void ESP32SJA1000Class::dumpRegisters(Stream& out)
 
 void ESP32SJA1000Class::handleInterrupt()
 {
-  uint8_t ir = readRegister(REG_IR);
-
-  if (ir & IR_EI) { // Error interrupt must be set to check for an error code
-    _onError(readRegister(REG_EIR), readRegister(REG_ECC));
-  } else if (ir & 0x01) {
-    // received packet, parse and call callback
-    parsePacket();
-    _onReceive(available());
-  } 
+  uint8_t ir;
+
+  // Loop to catch all interrupts
+  do {
+  	  uint8_t ir = readRegister(REG_IR); // Read interrupts
+  
+	  if (ir & IR_EI) { // Check error interrupt
+		  uint8_t ecc = readRegister(REG_ECC); // Get error code
+		  if (ecc != 0x00) {
+			  _onError(ir, ecc); // Trigger error buffering callback
+		  }
+	  }
+
+	  if (ir & 0x01) {
+		  // received packet, parse and call callback
+		  parsePacket();
+		  _onReceive(available()); // Trigger packet buffering callback
+	  } 
+  } while (ir); 
 }
 
 uint8_t ESP32SJA1000Class::readRegister(uint8_t address)
@@ -430,6 +468,21 @@ void ESP32SJA1000Class::onInterrupt(void* arg)
   ((ESP32SJA1000Class*)arg)->handleInterrupt();
 }
 
+SJA1000Status ESP32SJA1000Class::getStatus() {
+    SJA1000Status status;
+    status.apb_freq = ((READ_PERI_REG(RTC_APB_FREQ_REG)) & UINT16_MAX) << 12;
+    status.mode = CAN.readRegister(REG_MOD);
+    status.clk_div = CAN.readRegister(REG_CDR) & 0x07; // Bits 0-2 of CDR
+    status.btr0 = CAN.readRegister(REG_BTR0);
+    status.btr1 = CAN.readRegister(REG_BTR1);
+    // char bitrate_message[80];
+    // sprintf(bitrate_message, 
+        // "Mode: 0x%02x, APB: %i, CLK DIV: 0x%02x, BTR0: 0x%02x, BTR1: 0x%02x", 
+        // mode, apb_freq, clock_divider, btr0, btr1
+    // );
+    return status;
+}
+
 ESP32SJA1000Class CAN;
 
 #endif
diff --git a/src/ESP32SJA1000.h b/src/ESP32SJA1000.h
index b432dee..d266361 100644
--- a/src/ESP32SJA1000.h
+++ b/src/ESP32SJA1000.h
@@ -11,6 +11,11 @@
 #define DEFAULT_CAN_RX_PIN GPIO_NUM_4
 #define DEFAULT_CAN_TX_PIN GPIO_NUM_5
 
+struct SJA1000Status {
+    uint32_t apb_freq;
+    uint8_t mode, clk_div, btr0, btr1;
+};
+
 class ESP32SJA1000Class : public CANControllerClass {
 
 public:
@@ -40,6 +45,11 @@ class ESP32SJA1000Class : public CANControllerClass {
 
   void dumpRegisters(Stream& out);
   uint8_t readRegister(uint8_t address);
+  bool isTxBufferFree();
+  bool isTxComplete();
+  bool isBusRecessive();
+  bool isReadyToTransmit();
+  SJA1000Status getStatus();
 
 private:
   void reset();
@@ -56,6 +66,7 @@ class ESP32SJA1000Class : public CANControllerClass {
   gpio_num_t _txPin;
   bool _loopback;
   intr_handle_t _intrHandle;
+  bool _transmitting;
 };
 
 extern ESP32SJA1000Class CAN;

From 1b6f6d5e46b1298da2c030c3a4cd9c81da91756c Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Sun, 22 Jun 2025 15:46:26 +0000
Subject: [PATCH 06/17] Disentangled ESP and MCP loading and added
 isReadyToTransmit()

---
 src/ESP32SJA1000.cpp | 10 +++++-----
 src/MCP2515.cpp      | 16 ++++++----------
 src/MCP2515.h        |  5 +----
 3 files changed, 12 insertions(+), 19 deletions(-)

diff --git a/src/ESP32SJA1000.cpp b/src/ESP32SJA1000.cpp
index a51c091..191676a 100644
--- a/src/ESP32SJA1000.cpp
+++ b/src/ESP32SJA1000.cpp
@@ -471,10 +471,10 @@ void ESP32SJA1000Class::onInterrupt(void* arg)
 SJA1000Status ESP32SJA1000Class::getStatus() {
     SJA1000Status status;
     status.apb_freq = ((READ_PERI_REG(RTC_APB_FREQ_REG)) & UINT16_MAX) << 12;
-    status.mode = CAN.readRegister(REG_MOD);
-    status.clk_div = CAN.readRegister(REG_CDR) & 0x07; // Bits 0-2 of CDR
-    status.btr0 = CAN.readRegister(REG_BTR0);
-    status.btr1 = CAN.readRegister(REG_BTR1);
+    status.mode = readRegister(REG_MOD);
+    status.clk_div = readRegister(REG_CDR) & 0x07; // Bits 0-2 of CDR
+    status.btr0 = readRegister(REG_BTR0);
+    status.btr1 = readRegister(REG_BTR1);
     // char bitrate_message[80];
     // sprintf(bitrate_message, 
         // "Mode: 0x%02x, APB: %i, CLK DIV: 0x%02x, BTR0: 0x%02x, BTR1: 0x%02x", 
@@ -483,6 +483,6 @@ SJA1000Status ESP32SJA1000Class::getStatus() {
     return status;
 }
 
-ESP32SJA1000Class CAN;
+// ESP32SJA1000Class CAN;
 
 #endif
diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index 36c160d..8054086 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -1,8 +1,6 @@
 // Copyright (c) Sandeep Mistry. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
-#ifndef ARDUINO_ARCH_ESP32
-
 #include "MCP2515.h"
 
 #define REG_BFPCTRL                0x0c
@@ -260,6 +258,10 @@ int MCP2515Class::parsePacket()
   return _rxDlc;
 }
 
+bool MCP2515Class::isReadyToTransmit() {
+    return true;
+}
+
 void MCP2515Class::onReceive(void(*callback)(int))
 {
   CANControllerClass::onReceive(callback);
@@ -267,13 +269,9 @@ void MCP2515Class::onReceive(void(*callback)(int))
   pinMode(_intPin, INPUT);
 
   if (callback) {
-    SPI.usingInterrupt(digitalPinToInterrupt(_intPin));
     attachInterrupt(digitalPinToInterrupt(_intPin), MCP2515Class::onInterrupt, LOW);
   } else {
     detachInterrupt(digitalPinToInterrupt(_intPin));
-#ifdef SPI_HAS_NOTUSINGINTERRUPT
-    SPI.notUsingInterrupt(digitalPinToInterrupt(_intPin));
-#endif
   }
 }
 
@@ -489,9 +487,7 @@ void MCP2515Class::writeRegister(uint8_t address, uint8_t value)
 
 void MCP2515Class::onInterrupt()
 {
-  CAN.handleInterrupt();
+    CAN.handleInterrupt();
 }
 
-MCP2515Class CAN;
-
-#endif
+// MCP2515Class CAN;
diff --git a/src/MCP2515.h b/src/MCP2515.h
index 2f0444f..bbc5315 100644
--- a/src/MCP2515.h
+++ b/src/MCP2515.h
@@ -1,8 +1,6 @@
 // Copyright (c) Sandeep Mistry. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
-#ifndef ARDUINO_ARCH_ESP32
-
 #ifndef MCP2515_H
 #define MCP2515_H
 
@@ -35,6 +33,7 @@ class MCP2515Class : public CANControllerClass {
   virtual int parsePacket();
 
   virtual void onReceive(void(*callback)(int));
+  bool isReadyToTransmit();
 
   using CANControllerClass::filter;
   virtual int filter(int id, int mask);
@@ -73,5 +72,3 @@ class MCP2515Class : public CANControllerClass {
 extern MCP2515Class CAN;
 
 #endif
-
-#endif

From f5305b20fd603e11487926a959531371adf9d0dd Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Sun, 22 Jun 2025 22:15:57 +0000
Subject: [PATCH 07/17] Cleaned up dumpRegisters, added some init return codes,
 and renamed reset to sendReset

---
 src/MCP2515.cpp | 20 ++++++++++++--------
 src/MCP2515.h   |  2 +-
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index 8054086..fb69247 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -74,13 +74,13 @@ int MCP2515Class::begin(long baudRate)
   pinMode(_csPin, OUTPUT);
 
   // start SPI
-  SPI.begin();
+  SPI.begin(18, 19, 23, 5); // SCK, MISO, MOSI, SS
 
-  reset();
+  sendReset();
 
   writeRegister(REG_CANCTRL, 0x80);
   if (readRegister(REG_CANCTRL) != 0x80) {
-    return 0;
+    return -1;
   }
 
   const struct {
@@ -127,7 +127,7 @@ int MCP2515Class::begin(long baudRate)
   }
 
   if (cnf == NULL) {
-    return 0;
+    return -2;
   }
 
   writeRegister(REG_CNF1, cnf[0]);
@@ -142,7 +142,7 @@ int MCP2515Class::begin(long baudRate)
 
   writeRegister(REG_CANCTRL, 0x00);
   if (readRegister(REG_CANCTRL) != 0x00) {
-    return 0;
+    return -3;
   }
 
   return 1;
@@ -417,15 +417,19 @@ void MCP2515Class::dumpRegisters(Stream& out)
       out.print('0');
     }
     out.print(i, HEX);
-    out.print(": 0x");
+    out.print(":0x");
     if (b < 16) {
       out.print('0');
     }
-    out.println(b, HEX);
+    out.print(b, HEX);
+	out.print(" ");
+    if (i % 8 == 7) {
+		out.println();
+	}
   }
 }
 
-void MCP2515Class::reset()
+void MCP2515Class::sendReset()
 {
   SPI.beginTransaction(_spiSettings);
   digitalWrite(_csPin, LOW);
diff --git a/src/MCP2515.h b/src/MCP2515.h
index bbc5315..d78505d 100644
--- a/src/MCP2515.h
+++ b/src/MCP2515.h
@@ -52,7 +52,7 @@ class MCP2515Class : public CANControllerClass {
   void dumpRegisters(Stream& out);
 
 private:
-  void reset();
+  void sendReset();
 
   void handleInterrupt();
 

From ba8a3b2add49fc6dc9feb158a9384b43a0ce14c8 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Mon, 23 Jun 2025 19:07:17 +0000
Subject: [PATCH 08/17] SPI debugging

---
 src/MCP2515.cpp | 33 +++++++++++++++++++++------------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index fb69247..13f972b 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -6,6 +6,7 @@
 #define REG_BFPCTRL                0x0c
 #define REG_TXRTSCTRL              0x0d
 
+#define REG_CANSTAT                0x0e
 #define REG_CANCTRL                0x0f
 
 #define REG_CNF3                   0x28
@@ -74,15 +75,19 @@ int MCP2515Class::begin(long baudRate)
   pinMode(_csPin, OUTPUT);
 
   // start SPI
-  SPI.begin(18, 19, 23, 5); // SCK, MISO, MOSI, SS
-
+  SPI.begin(18, 19, 23, _csPin); // SCK, MISO, MOSI, SS
+  delay(2000);
+	
   sendReset();
 
+  // 0x80 = Config mode
   writeRegister(REG_CANCTRL, 0x80);
-  if (readRegister(REG_CANCTRL) != 0x80) {
+  if ((readRegister(REG_CANSTAT) & 0xE0) != 0x80) {
     return -1;
   }
 
+  writeRegister(REG_CANCTRL, 0x04); // Enable CLKOUT
+
   const struct {
     long clockFrequency;
     long baudRate;
@@ -120,16 +125,18 @@ int MCP2515Class::begin(long baudRate)
   const uint8_t* cnf = NULL;
 
   for (unsigned int i = 0; i < (sizeof(CNF_MAPPER) / sizeof(CNF_MAPPER[0])); i++) {
-    if (CNF_MAPPER[i].clockFrequency == _clockFrequency && CNF_MAPPER[i].baudRate == baudRate) {
-      cnf = CNF_MAPPER[i].cnf;
-      break;
-    }
+	if (CNF_MAPPER[i].clockFrequency == _clockFrequency && CNF_MAPPER[i].baudRate == baudRate) {
+	  cnf = CNF_MAPPER[i].cnf;
+	  break;
+	}
   }
 
   if (cnf == NULL) {
-    return -2;
+	return -2;
   }
 
+  // uint8_t cnf[] = { 0x00, 0xB1, 0x04 };
+
   writeRegister(REG_CNF1, cnf[0]);
   writeRegister(REG_CNF2, cnf[1]);
   writeRegister(REG_CNF3, cnf[2]);
@@ -140,8 +147,10 @@ int MCP2515Class::begin(long baudRate)
   writeRegister(REG_RXBnCTRL(0), FLAG_RXM1 | FLAG_RXM0);
   writeRegister(REG_RXBnCTRL(1), FLAG_RXM1 | FLAG_RXM0);
 
+  // 0x00 = Normal mode
   writeRegister(REG_CANCTRL, 0x00);
-  if (readRegister(REG_CANCTRL) != 0x00) {
+
+  if ((readRegister(REG_CANSTAT) & 0xE0) != 0x00) {
     return -3;
   }
 
@@ -269,7 +278,7 @@ void MCP2515Class::onReceive(void(*callback)(int))
   pinMode(_intPin, INPUT);
 
   if (callback) {
-    attachInterrupt(digitalPinToInterrupt(_intPin), MCP2515Class::onInterrupt, LOW);
+    attachInterrupt(digitalPinToInterrupt(_intPin), MCP2515Class::onInterrupt, FALLING);
   } else {
     detachInterrupt(digitalPinToInterrupt(_intPin));
   }
@@ -436,8 +445,7 @@ void MCP2515Class::sendReset()
   SPI.transfer(0xc0);
   digitalWrite(_csPin, HIGH);
   SPI.endTransaction();
-
-  delayMicroseconds(10);
+  delayMicroseconds(100);
 }
 
 void MCP2515Class::handleInterrupt()
@@ -487,6 +495,7 @@ void MCP2515Class::writeRegister(uint8_t address, uint8_t value)
   SPI.transfer(value);
   digitalWrite(_csPin, HIGH);
   SPI.endTransaction();
+  delay(100);
 }
 
 void MCP2515Class::onInterrupt()

From 35bc4cc2c30a4d74253d1f8fc33e933f5e7c49e6 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Mon, 23 Jun 2025 21:20:04 +0000
Subject: [PATCH 09/17] Working implementation

---
 src/MCP2515.cpp | 60 +++++++++++++++++++++++++++++++------------------
 src/MCP2515.h   |  2 +-
 2 files changed, 39 insertions(+), 23 deletions(-)

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index 13f972b..b5050dc 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -54,10 +54,17 @@
 #define FLAG_RXM0                  0x20
 #define FLAG_RXM1                  0x40
 
+#define CMD_WRITE				   0x02
+#define CMD_READ				   0x03
+#define CMD_UPDATE				   0x05
+#define CMD_RESET				   0xC0
+
+#define CANSTAT_NORMAL 			   0x00
+#define CANSTAT_CONFIG 			   0x80
 
 MCP2515Class::MCP2515Class() :
   CANControllerClass(),
-  _spiSettings(10E6, MSBFIRST, SPI_MODE0),
+  _spiSettings(1E6, MSBFIRST, SPI_MODE0),
   _csPin(MCP2515_DEFAULT_CS_PIN),
   _intPin(MCP2515_DEFAULT_INT_PIN),
   _clockFrequency(MCP2515_DEFAULT_CLOCK_FREQUENCY)
@@ -77,17 +84,12 @@ int MCP2515Class::begin(long baudRate)
   // start SPI
   SPI.begin(18, 19, 23, _csPin); // SCK, MISO, MOSI, SS
   delay(2000);
-	
-  sendReset();
 
-  // 0x80 = Config mode
-  writeRegister(REG_CANCTRL, 0x80);
-  if ((readRegister(REG_CANSTAT) & 0xE0) != 0x80) {
-    return -1;
+  // Reset and verify that CANSTAT is in Config mode	
+  if (sendReset() != 1) {
+	return -4;
   }
 
-  writeRegister(REG_CANCTRL, 0x04); // Enable CLKOUT
-
   const struct {
     long clockFrequency;
     long baudRate;
@@ -135,11 +137,12 @@ int MCP2515Class::begin(long baudRate)
 	return -2;
   }
 
-  // uint8_t cnf[] = { 0x00, 0xB1, 0x04 };
-
   writeRegister(REG_CNF1, cnf[0]);
+  if (readRegister(REG_CNF1) != cnf[0]) { return -5; }
   writeRegister(REG_CNF2, cnf[1]);
+  if (readRegister(REG_CNF2) != cnf[1]) { return -6; }
   writeRegister(REG_CNF3, cnf[2]);
+  if (readRegister(REG_CNF3) != cnf[2]) { return -7; }
 
   writeRegister(REG_CANINTE, FLAG_RXnIE(1) | FLAG_RXnIE(0));
   writeRegister(REG_BFPCTRL, 0x00);
@@ -148,11 +151,12 @@ int MCP2515Class::begin(long baudRate)
   writeRegister(REG_RXBnCTRL(1), FLAG_RXM1 | FLAG_RXM0);
 
   // 0x00 = Normal mode
-  writeRegister(REG_CANCTRL, 0x00);
+  writeRegister(REG_CANCTRL, CANSTAT_NORMAL);
 
-  if ((readRegister(REG_CANSTAT) & 0xE0) != 0x00) {
+  if ((readRegister(REG_CANSTAT) & 0xE0) != CANSTAT_NORMAL) {
     return -3;
   }
+  
 
   return 1;
 }
@@ -438,14 +442,28 @@ void MCP2515Class::dumpRegisters(Stream& out)
   }
 }
 
-void MCP2515Class::sendReset()
+int MCP2515Class::sendReset()
 {
   SPI.beginTransaction(_spiSettings);
   digitalWrite(_csPin, LOW);
-  SPI.transfer(0xc0);
+  SPI.transfer(CMD_RESET);
+  digitalWrite(_csPin, HIGH);
+  delay(10);
+  
+  // Read CANSTAT (cmd 0x03, address 0x0E)
+  digitalWrite(_csPin, LOW);
+  SPI.transfer(CMD_READ);     // READ command
+  SPI.transfer(REG_CANSTAT);     // CANSTAT address
+  uint8_t canstat = SPI.transfer(0x00);  // read value
   digitalWrite(_csPin, HIGH);
   SPI.endTransaction();
-  delayMicroseconds(100);
+
+  // CANSTAT 0x80 == config mode
+  if (canstat != CANSTAT_CONFIG) {
+	return -1;
+  }
+
+  return 1;
 }
 
 void MCP2515Class::handleInterrupt()
@@ -462,15 +480,13 @@ void MCP2515Class::handleInterrupt()
 uint8_t MCP2515Class::readRegister(uint8_t address)
 {
   uint8_t value;
-
   SPI.beginTransaction(_spiSettings);
   digitalWrite(_csPin, LOW);
-  SPI.transfer(0x03);
+  SPI.transfer(CMD_READ);
   SPI.transfer(address);
   value = SPI.transfer(0x00);
   digitalWrite(_csPin, HIGH);
   SPI.endTransaction();
-
   return value;
 }
 
@@ -478,7 +494,7 @@ void MCP2515Class::modifyRegister(uint8_t address, uint8_t mask, uint8_t value)
 {
   SPI.beginTransaction(_spiSettings);
   digitalWrite(_csPin, LOW);
-  SPI.transfer(0x05);
+  SPI.transfer(CMD_UPDATE);
   SPI.transfer(address);
   SPI.transfer(mask);
   SPI.transfer(value);
@@ -490,12 +506,12 @@ void MCP2515Class::writeRegister(uint8_t address, uint8_t value)
 {
   SPI.beginTransaction(_spiSettings);
   digitalWrite(_csPin, LOW);
-  SPI.transfer(0x02);
+  SPI.transfer(CMD_WRITE);
   SPI.transfer(address);
   SPI.transfer(value);
   digitalWrite(_csPin, HIGH);
   SPI.endTransaction();
-  delay(100);
+  // delay(10);
 }
 
 void MCP2515Class::onInterrupt()
diff --git a/src/MCP2515.h b/src/MCP2515.h
index d78505d..4c611b5 100644
--- a/src/MCP2515.h
+++ b/src/MCP2515.h
@@ -52,7 +52,7 @@ class MCP2515Class : public CANControllerClass {
   void dumpRegisters(Stream& out);
 
 private:
-  void sendReset();
+  int sendReset();
 
   void handleInterrupt();
 

From 85bbf20b5a9f0e0b99fca867cf78164acd54812a Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Tue, 24 Jun 2025 02:56:28 +0000
Subject: [PATCH 10/17] Simplify callback definitions

---
 src/CANController.h |  6 ++++--
 src/MCP2515.cpp     | 10 ++--------
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/src/CANController.h b/src/CANController.h
index 6e7cbc4..8a7b6a1 100644
--- a/src/CANController.h
+++ b/src/CANController.h
@@ -6,8 +6,10 @@
 
 #include <Arduino.h>
 
-typedef std::function<void (int packetSize)> TCallback;
-typedef std::function<void (int eir, int ecc)> TErrorCallback;
+// typedef std::function<void (int packetSize)> TCallback;
+// typedef std::function<void (int eir, int ecc)> TErrorCallback;
+typedef void (*TCallback)(int);
+typedef void (*TErrorCallback)(int, int);
 
 class CANControllerClass : public Stream {
 
diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index b5050dc..8791075 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -275,17 +275,11 @@ bool MCP2515Class::isReadyToTransmit() {
     return true;
 }
 
-void MCP2515Class::onReceive(void(*callback)(int))
+void MCP2515Class::onReceive(TCallback callback)
 {
   CANControllerClass::onReceive(callback);
-
   pinMode(_intPin, INPUT);
-
-  if (callback) {
-    attachInterrupt(digitalPinToInterrupt(_intPin), MCP2515Class::onInterrupt, FALLING);
-  } else {
-    detachInterrupt(digitalPinToInterrupt(_intPin));
-  }
+  attachInterrupt(digitalPinToInterrupt(_intPin), MCP2515Class::onInterrupt, FALLING);
 }
 
 int MCP2515Class::filter(int id, int mask)

From eaa80726e9a0cd2e6a118b9574ac4ec9fbc72410 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Tue, 24 Jun 2025 14:32:13 +0000
Subject: [PATCH 11/17] Debug handler

---
 src/MCP2515.cpp | 10 ++++++++++
 src/MCP2515.h   |  3 ++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index 8791075..87c1deb 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -62,6 +62,8 @@
 #define CANSTAT_NORMAL 			   0x00
 #define CANSTAT_CONFIG 			   0x80
 
+Stream* MCP2515Class::_debug;
+
 MCP2515Class::MCP2515Class() :
   CANControllerClass(),
   _spiSettings(1E6, MSBFIRST, SPI_MODE0),
@@ -397,6 +399,10 @@ int MCP2515Class::wakeup()
 
   return 1;
 }
+  
+void MCP2515Class::setDebugOutput(Stream* debug) {
+    _debug = debug;
+}
 
 void MCP2515Class::setPins(int cs, int irq)
 {
@@ -462,6 +468,10 @@ int MCP2515Class::sendReset()
 
 void MCP2515Class::handleInterrupt()
 {
+  if (_debug != nullptr) {
+    _debug->println("handleInterrupt called");
+  }
+
   if (readRegister(REG_CANINTF) == 0) {
     return;
   }
diff --git a/src/MCP2515.h b/src/MCP2515.h
index 4c611b5..e7fc0cc 100644
--- a/src/MCP2515.h
+++ b/src/MCP2515.h
@@ -5,7 +5,6 @@
 #define MCP2515_H
 
 #include <SPI.h>
-
 #include "CANController.h"
 
 #define MCP2515_DEFAULT_CLOCK_FREQUENCY 16e6
@@ -48,6 +47,7 @@ class MCP2515Class : public CANControllerClass {
   void setPins(int cs = MCP2515_DEFAULT_CS_PIN, int irq = MCP2515_DEFAULT_INT_PIN);
   void setSPIFrequency(uint32_t frequency);
   void setClockFrequency(long clockFrequency);
+  static void setDebugOutput(Stream* debug);
 
   void dumpRegisters(Stream& out);
 
@@ -64,6 +64,7 @@ class MCP2515Class : public CANControllerClass {
 
 private:
   SPISettings _spiSettings;
+  static Stream* _debug;
   int _csPin;
   int _intPin;
   long _clockFrequency;

From c45851b38c83f78b69c995ee9737160bb9e5ced3 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Tue, 24 Jun 2025 19:41:19 +0000
Subject: [PATCH 12/17] Only call parsePacket once per interrupt

---
 src/MCP2515.cpp | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index 87c1deb..7605c41 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -62,6 +62,10 @@
 #define CANSTAT_NORMAL 			   0x00
 #define CANSTAT_CONFIG 			   0x80
 
+#define FLAG_TX0IF 0x04  // Bit 2
+#define FLAG_TX1IF 0x08  // Bit 3
+#define FLAG_TX2IF 0x10  // Bit 4
+
 Stream* MCP2515Class::_debug;
 
 MCP2515Class::MCP2515Class() :
@@ -231,9 +235,9 @@ int MCP2515Class::parsePacket()
 
   uint8_t intf = readRegister(REG_CANINTF);
 
-  if (intf & FLAG_RXnIF(0)) {
+  if (intf & FLAG_RXnIF(0)) { // CAN message is available in RX buffer 0
     n = 0;
-  } else if (intf & FLAG_RXnIF(1)) {
+  } else if (intf & FLAG_RXnIF(1)) { // CAN message is available in RX buffer 1
     n = 1;
   } else {
     _rxId = -1;
@@ -255,6 +259,7 @@ int MCP2515Class::parsePacket()
     _rxId = idA;
     _rxRtr = (readRegister(REG_RXBnSIDL(n)) & FLAG_SRR) ? true : false;
   }
+
   _rxDlc = readRegister(REG_RXBnDLC(n)) & 0x0f;
   _rxIndex = 0;
 
@@ -472,13 +477,22 @@ void MCP2515Class::handleInterrupt()
     _debug->println("handleInterrupt called");
   }
 
-  if (readRegister(REG_CANINTF) == 0) {
-    return;
+  if (!(readRegister(REG_CANINTF) & (FLAG_RXnIF(0) | FLAG_RXnIF(1)))) {
+    return; // no frame in RXB0 or RXB1
   }
 
-  while (parsePacket() || _rxId != -1) {
+  int result = parsePacket();
+
+  if (result > 0) {
+      if (_debug != nullptr) {
+        _debug->print("parsePacket result:");
+        _debug->println(result);
+      }
     _onReceive(available());
   }
+
+  _rxId = -1; // Mark buffer as consumed
+
 }
 
 uint8_t MCP2515Class::readRegister(uint8_t address)

From bd7d6b4ae0191cdf258d13840a84690b0bc770cc Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Tue, 24 Jun 2025 23:54:04 +0000
Subject: [PATCH 13/17] State checking and error reporting

---
 src/MCP2515.cpp | 67 +++++++++++++++++++++++++++++++++++++++----------
 src/MCP2515.h   |  1 +
 2 files changed, 55 insertions(+), 13 deletions(-)

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index 7605c41..adf72f8 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -66,6 +66,12 @@
 #define FLAG_TX1IF 0x08  // Bit 3
 #define FLAG_TX2IF 0x10  // Bit 4
 
+#define FLAG_ERRIF  0x20 // bit 5 of REG_CANINTF (0x2C) 
+#define REG_EFLG    0x2D // Error Flag Register
+#define REG_TEC     0x1C // Transmit Error Counter
+#define REG_REC     0x1D // Receive Error Counter
+
+
 Stream* MCP2515Class::_debug;
 
 MCP2515Class::MCP2515Class() :
@@ -180,8 +186,21 @@ int MCP2515Class::endPacket()
     return 0;
   }
 
-  int n = 0;
+  // 1) pick a free mailbox
+  int n = -1;
+  for (int i = 0; i < 3; i++) {
+	  if (!(readRegister(REG_TXBnCTRL(i)) & 0x08)) {  // TXREQ==0?
+		  n = i;
+		  break;
+	  }
+  }
+
+  if (n < 0) {
+	  // all three mailboxes busy!
+	  return 0;
+  }
 
+  // 2) load ID/DLC/data
   if (_txExtended) {
     writeRegister(REG_TXBnSIDH(n), _txId >> 21);
     writeRegister(REG_TXBnSIDL(n), (((_txId >> 18) & 0x07) << 5) | FLAG_EXIDE | ((_txId >> 16) & 0x03));
@@ -204,29 +223,40 @@ int MCP2515Class::endPacket()
     }
   }
 
+  // 3) request transmit
   writeRegister(REG_TXBnCTRL(n), 0x08);
 
+  // 4) wait for TXREQ to clear, or abort on MLOA/ABTF/timeout
+  unsigned long start = millis();
   bool aborted = false;
-
   while (readRegister(REG_TXBnCTRL(n)) & 0x08) {
-    if (readRegister(REG_TXBnCTRL(n)) & 0x10) {
-      // abort
+    uint8_t s = readRegister(REG_TXBnCTRL(n));
+    if (s & (0x10 /*ABTF*/ | 0x20 /*MLOA*/)) {
       aborted = true;
-
-      modifyRegister(REG_CANCTRL, 0x10, 0x10);
+      break;
+    }
+    if (millis() - start > 10) {
+      // force‐abort if no ACK
+      modifyRegister(REG_CANCTRL, 0x10, 0x10); // ABAT=1
+      while (readRegister(REG_TXBnCTRL(n)) & 0x08) yield();
+      modifyRegister(REG_CANCTRL, 0x10, 0x00); // ABAT=0
+      aborted = true;
+      break;
     }
-
     yield();
   }
 
-  if (aborted) {
-    // clear abort command
-    modifyRegister(REG_CANCTRL, 0x10, 0x00);
-  }
+  // Print the status
+  uint8_t s = readRegister(REG_TXBnCTRL(n));
+  _debug->printf("TXB%d CTRL=0x%02X  TXREQ=%d  ABTF=%d  MLOA=%d\n",
+		  n, s,
+		  !!(s & 0x08),
+		  !!(s & 0x10),
+		  !!(s & 0x20));
 
+  // 5) clear interrupts & return
   modifyRegister(REG_CANINTF, FLAG_TXnIF(n), 0x00);
-
-  return (readRegister(REG_TXBnCTRL(n)) & 0x70) ? 0 : 1;
+  return aborted ? 0 : 1;
 }
 
 int MCP2515Class::parsePacket()
@@ -425,6 +455,17 @@ void MCP2515Class::setClockFrequency(long clockFrequency)
   _clockFrequency = clockFrequency;
 }
 
+void MCP2515Class::dumpErrors() {
+	uint8_t intf = readRegister(REG_CANINTF);
+	if (intf & FLAG_ERRIF) {
+		uint8_t eflg = readRegister(REG_EFLG);
+		uint8_t tec  = readRegister(REG_TEC);
+		uint8_t rec  = readRegister(REG_REC);
+		_debug->printf("ERRIF! EFLG=0x%02X  TEC=%u  REC=%u\n", eflg, tec, rec);
+		modifyRegister(REG_CANINTF, FLAG_ERRIF, 0x00);
+	}
+}
+
 void MCP2515Class::dumpRegisters(Stream& out)
 {
   for (int i = 0; i < 128; i++) {
diff --git a/src/MCP2515.h b/src/MCP2515.h
index e7fc0cc..cd06f65 100644
--- a/src/MCP2515.h
+++ b/src/MCP2515.h
@@ -50,6 +50,7 @@ class MCP2515Class : public CANControllerClass {
   static void setDebugOutput(Stream* debug);
 
   void dumpRegisters(Stream& out);
+  void dumpErrors();
 
 private:
   int sendReset();

From 479b10a17fe5a5754d08161fd4ab7e3b00d1b836 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Wed, 25 Jun 2025 00:52:10 +0000
Subject: [PATCH 14/17] Disabled some debugging

---
 src/MCP2515.cpp | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index adf72f8..b9b2217 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -455,6 +455,7 @@ void MCP2515Class::setClockFrequency(long clockFrequency)
   _clockFrequency = clockFrequency;
 }
 
+// ERRIF! EFLG=0x0B  TEC=0  REC=128
 void MCP2515Class::dumpErrors() {
 	uint8_t intf = readRegister(REG_CANINTF);
 	if (intf & FLAG_ERRIF) {
@@ -514,9 +515,9 @@ int MCP2515Class::sendReset()
 
 void MCP2515Class::handleInterrupt()
 {
-  if (_debug != nullptr) {
-    _debug->println("handleInterrupt called");
-  }
+  // if (_debug != nullptr) {
+    // _debug->println("handleInterrupt called");
+  // }
 
   if (!(readRegister(REG_CANINTF) & (FLAG_RXnIF(0) | FLAG_RXnIF(1)))) {
     return; // no frame in RXB0 or RXB1
@@ -525,10 +526,10 @@ void MCP2515Class::handleInterrupt()
   int result = parsePacket();
 
   if (result > 0) {
-      if (_debug != nullptr) {
-        _debug->print("parsePacket result:");
-        _debug->println(result);
-      }
+      // if (_debug != nullptr) {
+        // _debug->print("parsePacket result:");
+        // _debug->println(result);
+      // }
     _onReceive(available());
   }
 

From 5ef4ac9847943d1a99976b03d6ddd61b6b416044 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Thu, 26 Jun 2025 16:44:18 +0000
Subject: [PATCH 15/17] Remove yields

---
 src/MCP2515.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index b9b2217..58a9948 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -238,12 +238,12 @@ int MCP2515Class::endPacket()
     if (millis() - start > 10) {
       // force‐abort if no ACK
       modifyRegister(REG_CANCTRL, 0x10, 0x10); // ABAT=1
-      while (readRegister(REG_TXBnCTRL(n)) & 0x08) yield();
+      while (readRegister(REG_TXBnCTRL(n)) & 0x08) // yield();
       modifyRegister(REG_CANCTRL, 0x10, 0x00); // ABAT=0
       aborted = true;
       break;
     }
-    yield();
+    // yield();
   }
 
   // Print the status

From bf18f8b1066260c2157023e32ea7d09565e68292 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Thu, 26 Jun 2025 17:15:58 +0000
Subject: [PATCH 16/17] Added nullptr checks

---
 src/MCP2515.cpp | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index 58a9948..5891607 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -248,11 +248,11 @@ int MCP2515Class::endPacket()
 
   // Print the status
   uint8_t s = readRegister(REG_TXBnCTRL(n));
-  _debug->printf("TXB%d CTRL=0x%02X  TXREQ=%d  ABTF=%d  MLOA=%d\n",
-		  n, s,
-		  !!(s & 0x08),
-		  !!(s & 0x10),
-		  !!(s & 0x20));
+  if (_debug != nullptr) {
+      _debug->printf("TXB%d CTRL=0x%02X  TXREQ=%d  ABTF=%d  MLOA=%d\n",
+              n, s, !!(s & 0x08), !!(s & 0x10), !!(s & 0x20));
+  }
+}
 
   // 5) clear interrupts & return
   modifyRegister(REG_CANINTF, FLAG_TXnIF(n), 0x00);
@@ -462,7 +462,11 @@ void MCP2515Class::dumpErrors() {
 		uint8_t eflg = readRegister(REG_EFLG);
 		uint8_t tec  = readRegister(REG_TEC);
 		uint8_t rec  = readRegister(REG_REC);
-		_debug->printf("ERRIF! EFLG=0x%02X  TEC=%u  REC=%u\n", eflg, tec, rec);
+
+        if (_debug != nullptr) {
+            _debug->printf("ERRIF! EFLG=0x%02X  TEC=%u  REC=%u\n", eflg, tec, rec);
+        }
+
 		modifyRegister(REG_CANINTF, FLAG_ERRIF, 0x00);
 	}
 }

From 21c56a113e2dc6617d095dd1badacc0e9e7d8743 Mon Sep 17 00:00:00 2001
From: "Bryan C. Geraghty" <archwisp@gmail.com>
Date: Thu, 26 Jun 2025 17:56:42 +0000
Subject: [PATCH 17/17] Renamed packet to frame for clarity

---
 src/CANController.cpp | 30 +++++++++++++++---------------
 src/CANController.h   | 20 ++++++++++----------
 src/ESP32SJA1000.cpp  | 18 +++++++++---------
 src/ESP32SJA1000.h    |  4 ++--
 src/MCP2515.cpp       | 11 +++++------
 src/MCP2515.h         |  4 ++--
 6 files changed, 43 insertions(+), 44 deletions(-)

diff --git a/src/CANController.cpp b/src/CANController.cpp
index 18b643b..b503b18 100644
--- a/src/CANController.cpp
+++ b/src/CANController.cpp
@@ -7,7 +7,7 @@ CANControllerClass::CANControllerClass() :
   _onReceive(NULL),
   _onError(NULL),
 
-  _packetBegun(false),
+  _frameBegun(false),
   _txId(-1),
   _txExtended(-1),
   _txRtr(false),
@@ -31,7 +31,7 @@ CANControllerClass::~CANControllerClass()
 
 int CANControllerClass::begin(long /*baudRate*/)
 {
-  _packetBegun = false;
+  _frameBegun = false;
   _txId = -1;
   _txRtr =false;
   _txDlc = 0;
@@ -50,7 +50,7 @@ void CANControllerClass::end()
 {
 }
 
-int CANControllerClass::beginPacket(int id, int dlc, bool rtr)
+int CANControllerClass::beginFrame(int id, int dlc, bool rtr)
 {
   if (id < 0 || id > 0x7FF) {
     return 0;
@@ -60,7 +60,7 @@ int CANControllerClass::beginPacket(int id, int dlc, bool rtr)
     return 0;
   }
 
-  _packetBegun = true;
+  _frameBegun = true;
   _txId = id;
   _txExtended = false;
   _txRtr = rtr;
@@ -72,7 +72,7 @@ int CANControllerClass::beginPacket(int id, int dlc, bool rtr)
   return 1;
 }
 
-int CANControllerClass::beginExtendedPacket(long id, int dlc, bool rtr)
+int CANControllerClass::beginExtendedFrame(long id, int dlc, bool rtr)
 {
   if (id < 0 || id > 0x1FFFFFFF) {
     return 0;
@@ -82,7 +82,7 @@ int CANControllerClass::beginExtendedPacket(long id, int dlc, bool rtr)
     return 0;
   }
 
-  _packetBegun = true;
+  _frameBegun = true;
   _txId = id;
   _txExtended = true;
   _txRtr = rtr;
@@ -94,12 +94,12 @@ int CANControllerClass::beginExtendedPacket(long id, int dlc, bool rtr)
   return 1;
 }
 
-int CANControllerClass::endPacket()
+int CANControllerClass::endFrame()
 {
-  if (!_packetBegun) {
+  if (!_frameBegun) {
     return 0;
   }
-  _packetBegun = false;
+  _frameBegun = false;
 
   if (_txDlc >= 0) {
     _txLength = _txDlc;
@@ -108,27 +108,27 @@ int CANControllerClass::endPacket()
   return 1;
 }
 
-int CANControllerClass::parsePacket()
+int CANControllerClass::parseFrame()
 {
   return 0;
 }
 
-long CANControllerClass::packetId()
+long CANControllerClass::frameId()
 {
   return _rxId;
 }
 
-bool CANControllerClass::packetExtended()
+bool CANControllerClass::frameExtended()
 {
   return _rxExtended;
 }
 
-bool CANControllerClass::packetRtr()
+bool CANControllerClass::frameRtr()
 {
   return _rxRtr;
 }
 
-int CANControllerClass::packetDlc()
+int CANControllerClass::frameDlc()
 {
   return _rxDlc;
 }
@@ -140,7 +140,7 @@ size_t CANControllerClass::write(uint8_t byte)
 
 size_t CANControllerClass::write(const uint8_t *buffer, size_t size)
 {
-  if (!_packetBegun) {
+  if (!_frameBegun) {
     return 0;
   }
 
diff --git a/src/CANController.h b/src/CANController.h
index 8a7b6a1..798e23c 100644
--- a/src/CANController.h
+++ b/src/CANController.h
@@ -6,7 +6,7 @@
 
 #include <Arduino.h>
 
-// typedef std::function<void (int packetSize)> TCallback;
+// typedef std::function<void (int frameSize)> TCallback;
 // typedef std::function<void (int eir, int ecc)> TErrorCallback;
 typedef void (*TCallback)(int);
 typedef void (*TErrorCallback)(int, int);
@@ -17,15 +17,15 @@ class CANControllerClass : public Stream {
   virtual int begin(long baudRate);
   virtual void end();
 
-  int beginPacket(int id, int dlc = -1, bool rtr = false);
-  int beginExtendedPacket(long id, int dlc = -1, bool rtr = false);
-  virtual int endPacket();
+  int beginFrame(int id, int dlc = -1, bool rtr = false);
+  int beginExtendedFrame(long id, int dlc = -1, bool rtr = false);
+  virtual int endFrame();
 
-  virtual int parsePacket();
-  long packetId();
-  bool packetExtended();
-  bool packetRtr();
-  int packetDlc();
+  virtual int parseFrame();
+  long frameId();
+  bool frameExtended();
+  bool frameRtr();
+  int frameDlc();
 
   // from Print
   virtual size_t write(uint8_t byte);
@@ -58,7 +58,7 @@ class CANControllerClass : public Stream {
   TCallback _onReceive;
   TErrorCallback _onError;
 
-  bool _packetBegun;
+  bool _frameBegun;
   long _txId;
   bool _txExtended;
   bool _txRtr;
diff --git a/src/ESP32SJA1000.cpp b/src/ESP32SJA1000.cpp
index 191676a..ee01f87 100644
--- a/src/ESP32SJA1000.cpp
+++ b/src/ESP32SJA1000.cpp
@@ -108,7 +108,7 @@ int ESP32SJA1000Class::begin(long baudRate)
 	  // So let's do some experiments
 
 	  // 20 Mhz = 20E6/500E3 = 40 = 2x20; brp=2; 20x.75=15 (75% sample point); tseg1=15; 20-15=5; tseg2=5;
-	  // Acks first scanner packet, sends response, scaner acks, triggers CAN error on next scanner tx bit
+	  // Acks first scanner frame, sends response, scaner acks, triggers CAN error on next scanner tx bit
 	  sjw = 2; ts = 0; brp = 2, tseg1 = 15, tseg2 = 5;
 	  
 	  // Same: sjw = 2; ts = 0; brp = 2, tseg1 = 14, tseg2 = 6;
@@ -116,7 +116,7 @@ int ESP32SJA1000Class::begin(long baudRate)
 	  // sjw = 2; ts = 0; brp = 2, tseg1 = 16, tseg2 = 4;
 
 	  // 24 Mhz = 24E6/500E3 = 48 = 3x16; brp=3; 16x.75=12, tseg1=12; 16-12=4; tseg2=4;
-	  // Triggers error on first scanner packet CRC
+	  // Triggers error on first scanner frame CRC
 	  // sjw = 3; ts = 0; brp = 3, tseg1 = 12, tseg2 = 4;
 	  
 	  // 12 Mhz = 12E6/500E3 = 24 = 1x24; brp=1; 24*.75=18; tseg1=18; 24-18=6; tseg2=6; 
@@ -207,9 +207,9 @@ bool ESP32SJA1000Class::isReadyToTransmit() {
 	return isTxBufferFree() && isBusRecessive();
 }
 
-int ESP32SJA1000Class::endPacket()
+int ESP32SJA1000Class::endFrame()
 {
-  if (!CANControllerClass::endPacket()) {
+  if (!CANControllerClass::endFrame()) {
     return 0;
   }
 
@@ -262,10 +262,10 @@ int ESP32SJA1000Class::endPacket()
   return 1;
 }
 
-int ESP32SJA1000Class::parsePacket()
+int ESP32SJA1000Class::parseFrame()
 {
   if ((readRegister(REG_SR) & 0x01) != 0x01) {
-    // no packet
+    // no frame
     return 0;
   }
 
@@ -435,9 +435,9 @@ void ESP32SJA1000Class::handleInterrupt()
 	  }
 
 	  if (ir & 0x01) {
-		  // received packet, parse and call callback
-		  parsePacket();
-		  _onReceive(available()); // Trigger packet buffering callback
+		  // received frame, parse and call callback
+		  parseFrame();
+		  _onReceive(available()); // Trigger frame buffering callback
 	  } 
   } while (ir); 
 }
diff --git a/src/ESP32SJA1000.h b/src/ESP32SJA1000.h
index d266361..5389532 100644
--- a/src/ESP32SJA1000.h
+++ b/src/ESP32SJA1000.h
@@ -25,9 +25,9 @@ class ESP32SJA1000Class : public CANControllerClass {
   virtual int begin(long baudRate);
   virtual void end();
 
-  virtual int endPacket();
+  virtual int endFrame();
 
-  virtual int parsePacket();
+  virtual int parseFrame();
 
   virtual void onReceive(TCallback callback);
 
diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index 5891607..9ab82a0 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -180,9 +180,9 @@ void MCP2515Class::end()
   CANControllerClass::end();
 }
 
-int MCP2515Class::endPacket()
+int MCP2515Class::endFrame()
 {
-  if (!CANControllerClass::endPacket()) {
+  if (!CANControllerClass::endFrame()) {
     return 0;
   }
 
@@ -252,14 +252,13 @@ int MCP2515Class::endPacket()
       _debug->printf("TXB%d CTRL=0x%02X  TXREQ=%d  ABTF=%d  MLOA=%d\n",
               n, s, !!(s & 0x08), !!(s & 0x10), !!(s & 0x20));
   }
-}
 
   // 5) clear interrupts & return
   modifyRegister(REG_CANINTF, FLAG_TXnIF(n), 0x00);
   return aborted ? 0 : 1;
 }
 
-int MCP2515Class::parsePacket()
+int MCP2515Class::parseFrame()
 {
   int n;
 
@@ -527,11 +526,11 @@ void MCP2515Class::handleInterrupt()
     return; // no frame in RXB0 or RXB1
   }
 
-  int result = parsePacket();
+  int result = parseFrame();
 
   if (result > 0) {
       // if (_debug != nullptr) {
-        // _debug->print("parsePacket result:");
+        // _debug->print("parseFrame result:");
         // _debug->println(result);
       // }
     _onReceive(available());
diff --git a/src/MCP2515.h b/src/MCP2515.h
index cd06f65..f3c4c1c 100644
--- a/src/MCP2515.h
+++ b/src/MCP2515.h
@@ -27,9 +27,9 @@ class MCP2515Class : public CANControllerClass {
   virtual int begin(long baudRate);
   virtual void end();
 
-  virtual int endPacket();
+  virtual int endFrame();
 
-  virtual int parsePacket();
+  virtual int parseFrame();
 
   virtual void onReceive(void(*callback)(int));
   bool isReadyToTransmit();