CAN implementation for the MC9S12C128 Freescale controller

[saudrehman]

hi guys,
i am supposed to write application programs for sending and receiving data from PC (RS232 vi)a CAN Bus using the MC9S12C128 Freescale controller which has a MsCAN module.i have two boards and i have to send data fromPC to one of the boards which will convert it into a Can Frame and send it to the other board which will receive it and send back to PC .
how should i go about writing the code.i have read and re-read the controller data sheets but have no clue on how to implement it.
how should i go abt it?
please help.

 

[marie65]

CAN Implementation

First off all, you have to decide for a communication protocol or to create one. The CAN frame is limited to 8 bytes. If you want to transmit from PC, messages with more then 8 bytes then you have to think how the message will be fragmented and pack inside the CAN messages. Also you have to decide if you use ACK reply for packets.
I don't have any experience with MC9S12C128, but the principles have to be the same with other CAN controllers:
if we suppose that your messages are shorter then 8 bytes you have to assign an ID for CAN telegram (different for each node), set the reception filter for that ID at the receiver node and transfer the serial received bytes in CAN data registers. Start the CAN transmision and at reception node, poll the CAN reception flag. Took the data from CAN receiver registers when the telegram arrived and transfer it to PC trough serial.
Looks simple but it isn't. You will have to set all the CAN parameters carefully, in order to work. And don't forget the 120 ohm line terminations.

 

[xscale]

CAN Implementation

you can dld CAST CAN design pdf

www.buswares.com

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