V3: add I2C. Add I/O note to porting guide.

Author: peterhinch

v3/as_drivers/i2c/asi2c.py

@@ -160,7 +160,7 @@ async def _run(self):
     # On Pyboard blocks for 380μs to 1.2ms for small amounts of data
     def _handler(self, _, sn=bytearray(2), txnull=bytearray(2)):
         addr = Responder.addr
-        self.rem.irq(handler=None, trigger=machine.Pin.IRQ_RISING)
+        self.rem.irq(handler=None)
         utime.sleep_us(_DELAY)  # Ensure Initiator has set up to write.
         self.i2c.readfrom_into(addr, sn)
         self.own(1)

v3/as_drivers/i2c/asi2c_i.py

@@ -86,8 +86,7 @@ async def _run(self):
                     tstart = utime.ticks_us()
                     self._sendrx()
                     t = utime.ticks_diff(utime.ticks_us(), tstart)
-                except OSError as e:
-#                    print('OSError:', e)  # TEST
+                except OSError:  # Reboot remote.
                     break
                 await asyncio.sleep_ms(Initiator.t_poll)
                 self.block_max = max(self.block_max, t)  # self measurement
@@ -99,27 +98,26 @@ async def _run(self):
             if self.reset is None:  # No means of recovery
                 raise OSError('Responder fail.')
 
-    # Send payload length (may be 0) then payload (if any)
-    def _sendrx(self, sn=bytearray(2), txnull=bytearray(2)):
-        siz = self.txsiz if self.cantx else txnull
-        if self.rxbyt:
-            siz[1] |= 0x80  # Hold off further received data
-        else:
-            siz[1] &= 0x7f
+    def _send(self, d):
         # CRITICAL TIMING. Trigger interrupt on responder immediately before
         # send. Send must start before RX begins. Fast responders may need to
         # do a short blocking wait to guarantee this.
         self.own(1)  # Trigger interrupt.
-        self.i2c.send(siz)  # Blocks until RX complete.
+        self.i2c.send(d)  # Blocks until RX complete.
         self.waitfor(1)
         self.own(0)
         self.waitfor(0)
+
+    # Send payload length (may be 0) then payload (if any)
+    def _sendrx(self, sn=bytearray(2), txnull=bytearray(2)):
+        siz = self.txsiz if self.cantx else txnull
+        if self.rxbyt:
+            siz[1] |= 0x80  # Hold off further received data
+        else:
+            siz[1] &= 0x7f
+        self._send(siz)
         if self.txbyt and self.cantx:
-            self.own(1)
-            self.i2c.send(self.txbyt)
-            self.waitfor(1)
-            self.own(0)
-            self.waitfor(0)
+            self._send(self.txbyt)
             self._txdone()  # Invalidate source
         # Send complete
         self.waitfor(1)  # Wait for responder to request send
@@ -133,7 +131,6 @@ def _sendrx(self, sn=bytearray(2), txnull=bytearray(2)):
         self.cantx = not bool(sn[1] & 0x80)
         if n:
             self.waitfor(1)  # Wait for responder to request send
-            # print('setting up receive', n,' bytes')
             self.own(1)  # Acknowledge
             mv = self.rx_mv[0: n]  # mv is a memoryview instance
             self.i2c.recv(mv)

v3/as_drivers/i2c/i2c_esp.py

@@ -51,6 +51,7 @@ async def sender():
     swriter = asyncio.StreamWriter(chan, {})
     txdata = [0, 0]
     while True:
+        txdata[0] = gc.mem_free()
         await swriter.awrite(''.join((ujson.dumps(txdata), '\n')))
         txdata[1] += 1
         await asyncio.sleep_ms(1500)

v3/docs/I2C.md

@@ -376,6 +376,11 @@ chan = Initiator(i2c, syn, ack, rst, verbose, self._go, (), self._fail)
 
 # 5. Limitations
 
+Currently, on the ESP8266, the code is affected by
+[iss 5714](https://github.com/micropython/micropython/issues/5714). Unless the
+board is repeatedly pinged, the ESP8266 fails periodically and is rebooted by
+the Pyboard.
+
 ## 5.1 Blocking
 
 Exchanges of data occur via `Initiator._sendrx()`, a synchronous method. This