Add PIO-based SoftwareSPI enabling SPI on any pins (earlephilhower#2778)

* Add PIO-based SoftwareSPI enabling SPI on any pins

The Raspberry Pi team has a working PIO-based SPI interface.  Wrap it
to work like a hardware SPI interface, allowing SPI on any pin
combination.

Tested reading and writing an SD card using unmodified SD library.

* Add W5500 example

Good for testing, shows non-contiguous pin outs.

Author: earlephilhower

README.md

@@ -148,7 +148,7 @@ The RP2040 PIO state machines (SMs) are used to generate jitter-free:
 * I2S Input
 * I2S Output
 * Software UARTs (Serial ports)
-
+* Software SPIs
 
 # Installing via Arduino Boards Manager
 ## Windows-specific Notes

docs/spi.rst

@@ -28,6 +28,19 @@ pin itself, as is the standard way in Arduino.
 
 * The interrupt calls (``attachInterrupt``, and ``detachInterrpt``) are not implemented.
 
+Software SPI (Master Only)
+==========================
+
+Similar to ``SoftwareSerial``, ``SoftwareSPI`` creates a PIO based SPI interface that
+can be used in the same manner as the hardware SPI devices.  The constructor takes the
+pins desired, which can be any GPIO pins with the rule that if hardware CS is used then
+it must be on pin ``SCK + 1``.  Construct a ``SoftwareSPI`` object in your code as
+follows and use it as needed (i.e. pass it into ``SD.begin(_CS, softwareSPI);``
+
+.. code:: cpp
+
+    #include <SoftwareSPI.h>
+    SoftwareSPI softSPI(_sck, _miso, _mosi); // no HW CS support, any selection of pins can be used
 
 SPI Slave (SPISlave)
 ====================

libraries/SoftwareSPI/examples/FilesSoftwareSPI/FilesSoftwareSPI.ino

@@ -0,0 +1,84 @@
+/*
+  SD card basic file example with Software SPI
+
+  This example shows how to create and destroy an SD card file
+  The circuit:
+   SD card attached to Pico as follows:
+   ** SCK           - GPIO0
+   ** CS            - GPIO1
+   ** MISO (AKA RX) - GPIO2
+   ** MOSI (AKA TX) - GPIO3
+
+  created   Nov 2010
+  by David A. Mellis
+  modified 9 Apr 2012
+  by Tom Igoe
+
+  This example code is in the public domain.
+*/
+
+#include <SoftwareSPI.h>
+
+const int _SCK = 0;
+const int _CS = 1; // Must be SCK+1 for HW CS support
+const int _MISO = 2;
+const int _MOSI = 3;
+SoftwareSPI softSPI(_SCK, _MISO, _MOSI, _CS);
+
+#include <SD.h>
+
+File myFile;
+
+void setup() {
+  // Open serial communications and wait for port to open:
+  Serial.begin(115200);
+
+  do {
+    delay(100);  // wait for serial port to connect. Needed for native USB port only
+  } while (!Serial);
+
+  Serial.print("Initializing SD card...");
+
+  bool sdInitialized = false;
+  sdInitialized = SD.begin(_CS, softSPI);
+  if (!sdInitialized) {
+    Serial.println("initialization failed!");
+    return;
+  }
+  Serial.println("initialization done.");
+
+  if (SD.exists("example.txt")) {
+    Serial.println("example.txt exists.");
+  } else {
+    Serial.println("example.txt doesn't exist.");
+  }
+
+  // open a new file and immediately close it:
+  Serial.println("Creating example.txt...");
+  myFile = SD.open("example.txt", FILE_WRITE);
+  myFile.close();
+
+  // Check to see if the file exists:
+  if (SD.exists("example.txt")) {
+    Serial.println("example.txt exists.");
+  } else {
+    Serial.println("example.txt doesn't exist.");
+  }
+
+  // delete the file:
+  Serial.println("Removing example.txt...");
+  SD.remove("example.txt");
+
+  if (SD.exists("example.txt")) {
+    Serial.println("example.txt exists.");
+  } else {
+    Serial.println("example.txt doesn't exist.");
+  }
+}
+
+void loop() {
+  // nothing happens after setup finishes.
+}
+
+
+

libraries/SoftwareSPI/examples/W5500SoftwareSPI/W5500SoftwareSPI.ino

@@ -0,0 +1,98 @@
+/*
+    This sketch establishes a TCP connection to a "quote of the day" service.
+    It sends a "hello" message, and then prints received data.
+*/
+
+#include <W5500lwIP.h>
+
+const char* host = "djxmmx.net";
+const uint16_t port = 17;
+
+#include <SoftwareSPI.h>
+const int _SCK = 0;   // Any pin allowed
+const int _CS = 1;    // Must be SCK+1 for HW CS support
+const int _MISO = 28; // Note that MOSI and MISO don't need to be contiguous.  Any pins allowed
+const int _MOSI = 3;  // Any pin not used elsewhere
+const int _INT = 4;   // W5500 IRQ line
+
+SoftwareSPI softSPI(_SCK, _MISO, _MOSI, _CS);
+
+Wiznet5500lwIP eth(_CS, softSPI, _INT);
+
+void setup() {
+  Serial.begin(115200);
+  delay(5000);
+  Serial.println();
+  Serial.println();
+  Serial.println("Starting Ethernet port");
+
+  // Start the Ethernet port
+  if (!eth.begin()) {
+    Serial.println("No wired Ethernet hardware detected. Check pinouts, wiring.");
+    while (1) {
+      delay(1000);
+    }
+  }
+
+  while (!eth.connected()) {
+    Serial.print(".");
+    delay(500);
+  }
+
+  Serial.println("");
+  Serial.println("Ethernet connected");
+  Serial.println("IP address: ");
+  Serial.println(eth.localIP());
+}
+
+void loop() {
+  static bool wait = false;
+
+  Serial.print("connecting to ");
+  Serial.print(host);
+  Serial.print(':');
+  Serial.println(port);
+
+  // Use WiFiClient class to create TCP connections
+  WiFiClient client;
+  if (!client.connect(host, port)) {
+    Serial.println("connection failed");
+    delay(5000);
+    return;
+  }
+
+  // This will send a string to the server
+  Serial.println("sending data to server");
+  if (client.connected()) {
+    client.println("hello from RP2040");
+  }
+
+  // wait for data to be available
+  unsigned long timeout = millis();
+  while (client.available() == 0) {
+    if (millis() - timeout > 5000) {
+      Serial.println(">>> Client Timeout !");
+      client.stop();
+      delay(60000);
+      return;
+    }
+  }
+
+  // Read all the lines of the reply from server and print them to Serial
+  Serial.println("receiving from remote server");
+  // not testing 'client.connected()' since we do not need to send data here
+  while (client.available()) {
+    char ch = static_cast<char>(client.read());
+    Serial.print(ch);
+  }
+
+  // Close the connection
+  Serial.println();
+  Serial.println("closing connection");
+  client.stop();
+
+  if (wait) {
+    delay(300000);  // execute once every 5 minutes, don't flood remote service
+  }
+  wait = true;
+}

libraries/SoftwareSPI/keywords.txt

@@ -0,0 +1,43 @@
+#######################################
+# Syntax Coloring Map SPI
+#######################################
+
+#######################################
+# Instances (KEYWORD2)
+#######################################
+
+SoftwareSPI	KEYWORD1
+
+#######################################
+# Methods and Functions (KEYWORD2)
+#######################################
+begin	KEYWORD2
+end	KEYWORD2
+beginTransaction	KEYWORD2
+endTransaction	KEYWORD2
+SPISettings	KEYWORD2
+transfer	KEYWORD2
+transfer16	KEYWORD2
+setBitOrder	KEYWORD2
+setDataMode	KEYWORD2
+setClockDivider	KEYWORD2
+setSCK	KEYWORD2
+setMOSI	KEYWORD2
+setMISO	KEYWORD2
+setCS	KEYWORD2
+
+#######################################
+# Constants (LITERAL1)
+#######################################
+SPI_CLOCK_DIV4	LITERAL1
+SPI_CLOCK_DIV16	LITERAL1
+SPI_CLOCK_DIV64	LITERAL1
+SPI_CLOCK_DIV128	LITERAL1
+SPI_CLOCK_DIV2	LITERAL1
+SPI_CLOCK_DIV8	LITERAL1
+SPI_CLOCK_DIV32	LITERAL1
+SPI_CLOCK_DIV64	LITERAL1
+SPI_MODE0	LITERAL1
+SPI_MODE1	LITERAL1
+SPI_MODE2	LITERAL1
+SPI_MODE3	LITERAL1

libraries/SoftwareSPI/library.properties

@@ -0,0 +1,10 @@
+name=SoftwareSPI
+version=1.0
+author=Earle F. Philhower, III <[email protected]>
+maintainer=Earle F. Philhower, III <[email protected]>
+sentence=Uses the PIO to provide an SPI interface on any pin.
+paragraph=
+category=Signal Input/Output
+url=http://arduino.cc/en/Reference/SPI
+architectures=rp2040
+dot_a_linkage=true