CAN Communication issue (Bit Timing, Remote frames)

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
Not applicable
Hello,

I wrote an own Windows application which communicates through a VN1610 CANalyzer over a CAN-bus with a XC2768X microcontroller. The communication works good.

To understand the CAN protocol I still have some still not answered questions. I hope someone can help to answer them.

-Bit Timing: CAN nodes has to be synchronized because of the different running speed of uC and Canalyzer. I want to achieve a CAN-bus speed of 100kbaud. Should be the length of Phase_Seg1 and Phase_Seg2 and accordingly the sampling point the same in at all nodes ?

- I want to request data with my Canalyzer from a XC2768X controller. I send a remote frame with DLC content without data. When I send a remote frame to the XC2768X it successfully calls the ISR, where I send a message back with the same ID and data. The problem is, that before the ISR reacts to the remote frame, I get the same remote frame back. That causes problem in my application. Can it be that it is caused by an echo on the line?

- In my XC2768X program I want to receive 12 000 values (0-130 dez area) and store them in the RAM, which I get over the CAN bus. For testing purposes I already successfully sent and stored 30 values dynamically. If I want to store 12 000 values in the RAM is not enough space on the on-chip memory (12 000 values -> 12k RAM neccessary). Is it reasonable to add an external EEPROM to store these all values ? How big can I choose an array (XC2723X and XC2768X) from an onchip, to have still enough RAM for other functions ?

Thanks for your help
0 Likes
1 Reply
Not applicable
danme wrote:

Should be the length of Phase_Seg1 and Phase_Seg2 and accordingly the sampling point the same in at all nodes ?

Yes, you should arrange to have the Sample Point in all nodes at the same bit position.

danme wrote:

- I want to request data with my Canalyzer from a XC2768X controller. I send a remote frame with DLC content without data. When I send a remote frame to the XC2768X it successfully calls the ISR, where I send a message back with the same ID and data. The problem is, that before the ISR reacts to the remote frame, I get the same remote frame back. That causes problem in my application. Can it be that it is caused by an echo on the line?

No idea what happens here. Handling remote transmission request requires a special programming of the message object. The MO itself can answer the rtr frame. It is very unlikely that it sends a rtr frame back. And it is not possible that the cause is some signal echo on the bus line.
0 Likes