[help!!!!]how can i get to know the messages (using the send(msgs, timeout) func) have been successfully acked on the CANBUS? #1822

leijr · 2024-07-24T08:55:43Z

leijr
Jul 24, 2024

for example, i send msgs in a very high frequency, but i dont know if the msg i send successfully acked on the can bus.
i try to send next message after the previous message has been acked by the can bus
is there any functions or api can help me resolve this?
really appreciated!!! thank you very much

Tbruno25 · 2024-07-26T15:56:41Z

Tbruno25
Jul 26, 2024

What's the use case? The protocol itself handles ack's and you should never really need to verify this.

2 replies

leijr Jul 27, 2024
Author

i have checked the user docuemnt:
there is a api function called bus.send(msg, tiimeout=None). timeout (Optional[float]) – If > 0, wait up to this many seconds for message to be ACK’ed or for transmit queue to be ready depending on driver implementation.
but my purpose is sending many messages in a very high frequency in a python for loop, then check if the last message is send successfully.
the Pseudo code :
for i in range(1, len(send_data)):
msg = can.Message(arbitration_id=send_id, data=send_data[i], is_extended_id=False, dlc=len(send_data[i]), is_fd=is_fd)
self.bus.send(msg, timeout = 100)
# print("data", send_data[i])
36_service = [0x02, 0x36, 0xaa,.....]
self.bus.send(36_service)
uds_msg_response = self.bus.recv(timeout=0.01)

the upper code after i debug i found that i send too many message in the for loop , all the message are on the transmit queue to be sent, if i continue send a new uds message service and wait the uds response, the self.bus.recv will be timeout because of the vector are still sending the message on the transmit queque, and the response delayed and timeout
so i want to to know if the last message has been acked by the can bus, i continue sending the next new message by the following steps.

Tbruno25 Jul 28, 2024

I think I understand your reasoning, but why not simply increase the timeout?

If you don't want to do that for whatever reason, another option could be to utilize the receive_own_messages parameter during bus creation. I have no idea whether this will function the way you need but it's something to play around with. For example, you can verify you're able to receive the last message before transmitting the next --

import can

bus = can.Bus(channel="demo", interface="virtual", receive_own_messages=True)
message = can.Message(arbitration_id=0x123, data=[0x11, 0x22, 0x33, 0x44])

for _ in range(25):
    bus.send(message)
    
    while received := bus.recv():
        if received.arbitration_id == message.arbitration_id:
            if received.data == message.data:
                break

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[help!!!!]how can i get to know the messages (using the send(msgs, timeout) func) have been successfully acked on the CANBUS? #1822

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[help!!!!]how can i get to know the messages (using the send(msgs, timeout) func) have been successfully acked on the CANBUS? #1822

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