Olimex Support Forum

OLinuXino Android / Linux boards and System On Modules => AM3352 => Topic started by: vihai on March 16, 2017, 07:20:58 PM

Title: CAN continuously transmitting?
Post by: vihai on March 16, 2017, 07:20:58 PM

I'm doing some experiment on the EVB with the Olimex Debian SD. Everything seems to be fine during setup but looking on an oscilloscope I'm noticing the bus never going back to idle.

Well, I suppose that in CAN terms a idle bus is electrically idle, I'm not an expert in CAN buses ::)

Am I doing something wrong?
Title: Re: CAN continuously transmitting?
Post by: KeesZagers on March 17, 2017, 07:45:28 PM
Hello Vihai,
I'm not familiar with this hardware, but I guess I know what is happening on the CANbus. The CANbus should be idle on startup. However as soon as you start to send a message, the hardware is expecting at least one other participant on the CANbus. At the end of the CAN message it has a so-called ACK(nowledge) slot, in which it sets a recessive bit (1), but it is expecting a dominant bit (0), which is set by all the other participants on the bus, which have received the message correctly. As long as no other participants are on the bus, it will retry to send the message continuously. So nothing wrong with your hardware or software.