Merge pull request #1293 from jepler/jepler-feathercan

Add examples for upcoming Adafruit Feather M4 CAN guide

Author: ladyada

FeatherCAN_CircuitPython/listener-ack.py

@@ -0,0 +1,47 @@
+import struct
+
+import board
+import canio
+import digitalio
+
+# If the CAN transceiver has a standby pin, bring it out of standby mode
+if hasattr(board, 'CAN_STANDBY'):
+    standby = digitalio.DigitalInOut(board.CAN_STANDBY)
+    standby.switch_to_output(False)
+
+# If the CAN transceiver is powered by a boost converter, turn on its supply
+if hasattr(board, 'BOOST_ENABLE'):
+    standby = digitalio.DigitalInOut(board.CAN_STANDBY)
+    standby.switch_to_output(True)
+
+can = canio.CAN(rx=board.CAN_RX, tx=board.CAN_TX, baudrate=250_000, auto_restart=True)
+listener = can.listen(matches=[canio.Match(0x408)], timeout=.9)
+
+old_bus_state = None
+old_count = -1
+
+while True:
+    bus_state = can.state
+    if bus_state != old_bus_state:
+        print(f"Bus state changed to {bus_state}")
+        old_bus_state = bus_state
+
+    message = listener.receive()
+    if message is None:
+        print("No messsage received within timeout")
+        continue
+
+    data = message.data
+    if len(data) != 8:
+        print(f"Unusual message length {len(data)}")
+        continue
+
+    count, now_ms = struct.unpack("<II", data)
+    gap = count - old_count
+    old_count = count
+    print(f"received message: id={message.id:x} count={count} now_ms={now_ms}")
+    if gap != 1:
+        print(f"gap: {gap}")
+
+    print("Sending ACK")
+    can.send(canio.Message(id=0x409, data=struct.pack("<I", count)))

FeatherCAN_CircuitPython/listener.py

@@ -0,0 +1,44 @@
+import struct
+
+import board
+import canio
+import digitalio
+
+# If the CAN transceiver has a standby pin, bring it out of standby mode
+if hasattr(board, 'CAN_STANDBY'):
+    standby = digitalio.DigitalInOut(board.CAN_STANDBY)
+    standby.switch_to_output(False)
+
+# If the CAN transceiver is powered by a boost converter, turn on its supply
+if hasattr(board, 'BOOST_ENABLE'):
+    standby = digitalio.DigitalInOut(board.CAN_STANDBY)
+    standby.switch_to_output(True)
+
+can = canio.CAN(rx=board.CAN_RX, tx=board.CAN_TX, baudrate=250_000, auto_restart=True)
+listener = can.listen(matches=[canio.Match(0x408)], timeout=.9)
+
+old_bus_state = None
+old_count = -1
+
+while True:
+    bus_state = can.state
+    if bus_state != old_bus_state:
+        print(f"Bus state changed to {bus_state}")
+        old_bus_state = bus_state
+
+    message = listener.receive()
+    if message is None:
+        print("No messsage received within timeout")
+        continue
+
+    data = message.data
+    if len(data) != 8:
+        print(f"Unusual message length {len(data)}")
+        continue
+
+    count, now_ms = struct.unpack("<II", data)
+    gap = count - old_count
+    old_count = count
+    print(f"received message: count={count} now_ms={now_ms}")
+    if gap != 1:
+        print(f"gap: {gap}")

FeatherCAN_CircuitPython/sender-ack.py

@@ -0,0 +1,55 @@
+import struct
+import time
+
+import board
+import canio
+import digitalio
+
+# If the CAN transceiver has a standby pin, bring it out of standby mode
+if hasattr(board, 'CAN_STANDBY'):
+    standby = digitalio.DigitalInOut(board.CAN_STANDBY)
+    standby.switch_to_output(False)
+
+# If the CAN transceiver is powered by a boost converter, turn on its supply
+if hasattr(board, 'BOOST_ENABLE'):
+    standby = digitalio.DigitalInOut(board.CAN_STANDBY)
+    standby.switch_to_output(True)
+
+can = canio.CAN(rx=board.CAN_RX, tx=board.CAN_TX, baudrate=250_000, auto_restart=True)
+listener = can.listen(matches=[canio.Match(0x409)], timeout=.1)
+
+old_bus_state = None
+count = 0
+
+while True:
+    bus_state = can.state
+    if bus_state != old_bus_state:
+        print(f"Bus state changed to {bus_state}")
+        old_bus_state = bus_state
+
+    now_ms = (time.monotonic_ns() // 1_000_000) & 0xffffffff
+    print(f"Sending message: count={count} now_ms={now_ms}")
+
+    message = canio.Message(id=0x408, data=struct.pack("<II", count, now_ms))
+    while True:
+        can.send(message)
+
+        message_in = listener.receive()
+        if message_in is None:
+            print("No ACK received within timeout")
+            continue
+
+        data = message_in.data
+        if len(data) != 4:
+            print(f"Unusual message length {len(data)}")
+            continue
+
+        ack_count = struct.unpack("<I", data)[0]
+        if ack_count == count:
+            print(f"Received ACK")
+            break
+        else:
+            print(f"Received incorrect ACK: {ack_count} should be {count}")
+
+    time.sleep(.5)
+    count += 1

FeatherCAN_CircuitPython/sender.py

@@ -0,0 +1,36 @@
+import struct
+import time
+
+import board
+import canio
+import digitalio
+
+# If the CAN transceiver has a standby pin, bring it out of standby mode
+if hasattr(board, 'CAN_STANDBY'):
+    standby = digitalio.DigitalInOut(board.CAN_STANDBY)
+    standby.switch_to_output(False)
+
+# If the CAN transceiver is powered by a boost converter, turn on its supply
+if hasattr(board, 'BOOST_ENABLE'):
+    standby = digitalio.DigitalInOut(board.CAN_STANDBY)
+    standby.switch_to_output(True)
+
+can = canio.CAN(rx=board.CAN_RX, tx=board.CAN_TX, baudrate=250_000, auto_restart=True)
+
+old_bus_state = None
+count = 0
+
+while True:
+    bus_state = can.state
+    if bus_state != old_bus_state:
+        print(f"Bus state changed to {bus_state}")
+        old_bus_state = bus_state
+
+    now_ms = (time.monotonic_ns() // 1_000_000) & 0xffffffff
+    print(f"Sending message: count={count} now_ms={now_ms}")
+
+    message = canio.Message(id=0x408, data=struct.pack("<II", count, now_ms))
+    can.send(message)
+
+    time.sleep(.5)
+    count += 1