User/jvollmer/read can with submodule

.gitmodules

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+[submodule "sc1-data-format"]
+	path = sc1-data-format
+	url = git@github.com:badgerloop-software/sc1-data-format.git

README.md

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+Link to docs https://www.waveshare.com/wiki/RS485_CAN_HAT#Install_Library
+
+Create virtual environment using:
+
+- Windows: `virtualenv -p python3 .env`
+- Linux/MacOS: `python3 -m venv .env`

read_can_messages.py

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+import can
+import struct
+import time
+import logging
+from send_messages import transmit_can_message
+import argparse
+from typing import List, Dict, Any
+from dataclasses import dataclass, asdict
+import json
+
+"""
+Message structure: 
+.arbitration_id: id of the CAN message
+.data: the body content of the CAN message
+.timestamp: the timestamp of the CAN message
+"""
+
+
+@dataclass
+class SignalInfo:
+    name: str
+    bytes: int
+    type: str
+    units: str
+    nominal_min: int
+    nominal_max: int
+    subsystem: str
+
+
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s - %(levelname)s - %(message)s",
+    datefmt="%Y-%m-%d %H:%M:%S",
+)
+
+
+def preprocess_data_format(format: Dict[str, List[Any]]) -> Dict[str, Dict[int, Any]]:
+    """
+    Parse data format and return in a more friendly format for  CAN consumption:
+    <CAN ID>: {
+        <offset>: {
+            <category 1>: ...
+            ...
+        }
+        ...
+    },
+    ...
+    """
+    processed = {}
+    for key, s in format.items():
+        # Get the arbitration ID and offset
+        can_id = int(s[-2], base=16)
+        offset = s[-1]
+        # Drop the ID and offset
+        s = s[:-2]
+        # Add/Update the message data in the processed data format
+        p = processed.setdefault(can_id, {})
+        num_bytes = s[0]
+        data_type = s[1]
+        units = s[2]
+        nominal_min = s[3]
+        nominal_max = s[4]
+        subsystem = s[5]
+        signal_info = SignalInfo(
+            key, num_bytes, data_type, units, nominal_min, nominal_max, subsystem
+        )
+        p[offset] = signal_info
+
+    return processed
+
+
+with open("sc1-data-format/format.json", "r") as file:
+    data = json.load(file)
+
+signal_definitions = preprocess_data_format(data)
+
+
+class MyListener(can.Listener):
+    def on_message_received(self, message):
+        message_data = {
+            "id": message.arbitration_id,
+            "data": list(message.data),
+            "timestamp": message.timestamp,
+        }
+
+        # loop through signal definitions to find can_id
+        can_id = message_data["id"]
+        if can_id not in signal_definitions:
+            logging.error(f"CAN ID {can_id:0x} not found in signal definitions.")
+            return
+        signals = signal_definitions[can_id]
+        byte_array = bytes(message.data)
+
+        for offset, signals_info in signals.items():
+            logging.debug(f"Processing signal at offset {offset} for CAN ID {can_id:0x}")
+            print(offset)
+            print(signals_info)
+            data_type = signals_info.type
+            signal_name = signals_info.name
+            if data_type == "float":
+                if len(byte_array) < 4:
+                    logging.error(
+                        f"Insufficient data for float signal in CAN ID {can_id:0x}."
+                    )
+                    return
+                else:
+                    # Unpack the first 4 bytes as a little-endian float.
+                    float_value = struct.unpack("<f", byte_array[:4])[0]
+                    logging.debug(
+                        f"New Message: ID={can_id:0x},Name={signal_name} Value={float_value}, Time Stamp={message_data['timestamp']}"
+                    )
+            elif data_type == "boolean":
+                bool_value = bool((byte_array[0] >> offset) & 1)
+                logging.debug(
+                    f"New Message: ID={can_id:0x},Name={signal_name} Value={bool_value}, Time Stamp={message_data['timestamp']}"
+                )
+
+
+if __name__ == "__main__":
+    # Create a CAN bus connection
+    bus = can.interface.Bus(channel="can0", bustype="socketcan")
+
+    # set up listener
+    listener = MyListener()
+
+    # A Notifier runs in the background and listens for messages. When a new message arrives, it calls on_message in MyListener.
+    notifier = can.Notifier(bus, [listener])
+
+    try:
+        # create an infinite loop to keep listening to messages.
+        print("Listening for CAN messages... Press Ctrl+C to stop.")
+        parser = argparse.ArgumentParser(description="Specify the CAN channel.")
+        # Define a positional argument for channel
+        parser.add_argument("channel", type=str, help="CAN channel (e.g., can0, vcan0)")
+        args = parser.parse_args()
+        transmit_can_message()
+        while True:
+            time.sleep(1)
+            # Infinite loop to keep listening
+    except KeyboardInterrupt:
+        print("Stopping CAN receiver.")
+        notifier.stop()
+        bus.shutdown()

send_messages.py

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+#!/usr/bin/env python3
+import can
+import argparse
+import logging
+
+
+def transmit_can_message(channel="can0", bustype="socketcan"):
+    """
+    Initializes the CAN bus, prompts the user for message parameters,
+    and transmits the CAN message.
+    """
+    # Initialize the CAN bus interface
+    bus = can.interface.Bus(channel=channel, bustype=bustype)
+
+    # Prompt for the arbitration ID (CAN ID), this gets the arbitration id from the user and validates it
+    arb_id_input = input("Enter 3-digit hex message id (e.g. 0x123): ").strip()
+    try:
+        # Accept input as hex if it starts with 0x, otherwise assume hex too
+        arbitration_id = int(arb_id_input, 16)
+    except ValueError:
+        logging.error("Invalid data byte input.")
+        bus.shutdown()
+        return
+
+    # Prompt for data bytes input (as hex values) accepts users inputs as data.
+    data_input = input(
+        "Enter data bytes as hex values separated by spaces (e.g. '11 22 33 44'): "
+    ).strip()
+    try:
+        data_bytes = []
+        for byte_str in data_input.split():
+            # Convert each input to an integer (assumed hex)
+            data_byte = int(byte_str, 16)
+            if not (0 <= data_byte <= 255):
+                logging.debug(f"Byte out of range (0-255): {data_byte}")
+                bus.shutdown()
+                return
+            data_bytes.append(data_byte)
+    except ValueError:
+        logging.error("Invalid data byte input.")
+        bus.shutdown()
+        return
+
+    # Create the CAN message
+    msg = can.Message(
+        arbitration_id=arbitration_id, data=data_bytes, is_extended_id=False
+    )
+
+    # Send message using bus.send()
+    try:
+        bus.send(msg)
+        logging.debug(
+            f"Message sent successfully!\n Message Details: ID={msg.arbitration_id}, Data={msg.data}"
+        )
+    except can.CanError as e:
+        logging.error(f"Message failed to send: {e}")
+
+    # Cleanly shutdown the bus connection
+    bus.shutdown()
+
+
+if __name__ == "__main__":
+    # Allow user to input CAN channel
+    parser = argparse.ArgumentParser(description="Specify the CAN channel.")
+    # Define a positional argument for channel
+    parser.add_argument("channel", type=str, help="CAN channel (e.g., can0, vcan0)")
+    args = parser.parse_args()
+    # add logging
+    logging.basicConfig(
+        level=logging.INFO,
+        format="%(asctime)s - %(levelname)s - %(message)s",
+        datefmt="%Y-%m-%d %H:%M:%S",
+    )
+    transmit_can_message(args.channel)