Not able to transmit more than 8bytes single frame in can bus using python

[FarhatJ]

Describe the bug

I am trying to transmit more than 8 bytes of single frame size(CAN FD) for classci CAN channel using can.Message. Also using Vector Canoe Application on Windows.

To Reproduce

with concurrent.futures.ThreadPoolExecutor() as executor:
            future = executor.submit(self.listen_for_port, port=port)

            msg0 = can.Message(arbitration_id=0x580, dlc=15, is_fd=True,
                               is_extended_id=True, bitrate_switch=True,
                               data=[3, 3, 3, 3, 3, 3, 3, 3, 3, 3])

            msg1 = can.Message(arbitration_id=0x582, dlc=15, is_fd=True,
                               is_extended_id=True, bitrate_switch=True,
                               data=[3, 3, 3, 3, 3, 3, 3, 3, 3, 3])

            messages = [msg0, msg1]
            vbus1.send_messages(messages, 1000)
            time.sleep(2)
            udp_frames = future.result()

I am getting below error when data is more than 8.

When data is 8 or less than 8, transmission works

Expected behavior

Should be able to see more tahn 8 bytes of data on canoe can channel when data=[3, 3, 3, 3, 3, 3, 3, 3, 3, 3]

Additional context

OS and version: Windows Python version: 3.7.9 python-can version: 4.2.0 python-can interface/s (if applicable):

I though initially the issue is on isotp protocol so raised issue in Python-can-isotp repository but after few discussion suggestion was to raise issue in Python-can layer For more detail: https://github.com/pylessard/python-can-isotp/issues/85

[zariiii9003]

CAN 2.0 can not transmit more than 8 bytes per message. CAN FD can transmit up to 64 bytes. Instantiate the bus with fd=True to connect to a CAN FD bus.

[FarhatJ]

I have initalised fd=True: My can bus obj looks like this:

self.bus = can.Bus(channel=net_channel,
                           interface='vector',
                           receive_own_messages=True,
                           app_name='CANoe',
                           fd=True,
                           bitrate=500000)

Sending 2 different length of data:

data1=[3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3]) data2=[3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3]) DLC does vary first one is 14 and second one is 10 but i still do not see full data on single frame.

I even configured my can channel for CAN FD

Is there anything else that I am missing?

[zariiii9003]

According to your traceback, you did NOT set fd=True when you created the issue.

When you are connected, do you see two baud rates here or just one?

[FarhatJ]

@zariiii9003 yes you are correct, initially fd=True was not set, after your information I did set.

When I am connected to canoe application, I do see 2 Baud rates.

[FarhatJ]

I found the issue why I am not able to see the full data on CAN Channel. For isotp protocol to get full data of 64 bytes on single frame, parameter that i have set for data length are:

1. tx_data_length: 64,
2. tx_data_min_length: 64, # this makes sure my data length is 64, and dlc varies depending on the data I am sending

Is there any coresponding param for tx_data_min_length in can.Message() to be set, other than dlc??