Re: detect auto baud rate on can bus in linux driver.

["Heinz-Jürgen Oertel" <oe@emtas.de>]

[-- Attachment #1: Type: text/plain, Size: 1703 bytes --]

Am Sonntag, 27. April 2014, 20:01:35 schrieb Kurt Van Dijck:
> 
> Autobaud is, IMO, a userspace thing.
> The principle has been explained, and with iproute2 & candump piping into
> grep or wc, you could even make a shell script for that.


In can4linux it can be done in user space, like

int do_autobaud(can_fd)
{
int bitrate[] = {10, 20,  50, 125, 250, 500, 800, 1000 , 0};
int i;
int ret;
can_statuspar_t status;

	printf("\tswitch into listen only mode\n"); 
	set_lomode(can_fd, 1);
	/* for all possible bit rates */
	for (i = 0; ; i++) {
		if (bitrate[i] == 0) {
			ret = 0;
			break;
		}
		printf("\tTry %d Kbit/s\n", bitrate[i]);
		set_bitrate(can_fd, bitrate[i]);
		/* wait one second */
		sleep(1);
		ioctl(can_fd, CAN_IOCTL_STATUS, &status);
		/* printf("Rx buffer: %d\n", status.rx_buffer_used); */
		if (status.rx_buffer_used > 1) {
			printf("\t\tCould receive frames. Switch back to 
active mode\n");
			ret = bitrate[i];
			break;
		}
	}
	if (ret > 0) {
		/* bit rate detected */
		set_lomode(can_fd, 0);
	}
	return ret;
}


Of course the CAN controller should have a 'listen only' mode.

On a running EnergyBus it looks like:

using CAN device /dev/can1
doing auto bit rate detection now
take care that traffic is on the bus
        switch into listen only mode
        Try 10 Kbit/s
        Try 20 Kbit/s
        Try 50 Kbit/s
        Try 125 Kbit/s
        Try 250 Kbit/s
                Could receive frames. Switch back to active mode




-- 

Mit freundlichen Grüßen

    Heinz-Jürgen Oertel

-------------------------------------------------------------------------

emtas - your embedded solution partner
 

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 490 bytes --]