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