Posted on January 16, 2014 at 09:04Nothing weird in the ISR.
I used a standard example,
just added a few Pin toggles to follow with LEDs.
Don't see it entering the ISR during DEBUG Mode at all though.
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Got it - found the problem !
One of the mcp2551 chips (or both) is not working.
So I use the Diode circuit below, and got rid of the failed mcp2551 chips.
It enters into the ISR properly repeatedly on schedule now !
Data is not always perfect - but can solve that at my ease (via protocols).
Learned Notes:
1) Connecting CAN Tx to Rx on same Chip - will Not work. It will just continuously Resend without Receiving in the ISR. If it answered its own message - how could any other Node/Chip answer it then ?
2) Connecting TxRx to another chip RxTx with common Gnd does not work.
3) Can use Simpler DIODE circuit instead of a CAN chip which works somewhat ok. Link (2) micros together via a wire connected to the CAN RX lines and Diodes connecting the TX (as a drain) to the same line. And, using a common Gnd wire.
Micro1: Micro2:
CAN RX <-------+-------------+-------> CAN RX
| |
CAN TX >--|<--+ +-->|--< CAN TX
Gnd o-----------------------------------------o Gnd
This gives a lot simpler setup for Debugging.
