CAN header and EXT asm question

[retepsnikrep]

Interface board with SPI controlled MCP 2515 and line driver to use with non CAN enabled PIC's
https://www.aliexpress.com/item/1005006850683509.html

Line driver to use with CAN enabled PIC's.
https://www.aliexpress.com/item/1005006209071522.html

You get the idea.. Cheap as chips..

My YT channel has a lot of PIC CAN tinkering stuff. @retepsnikrep
On Insightcentral.net and the CRZforum.com is tons of stuff from over the years.

[retepsnikrep]

Earlier CAN MITM prototypes.

One using 16F1825 at 32mhz and one using 18F26K80 at 64mhz.

It was possible to drive one of those serial data to RCA video gadgets as well.
This made a nice little very cheap dash mounted text display for info and debugging.

[retepsnikrep]

Watch out for the slew rate control bit in PICS.
It defaults to on in the PIC18F26K80!

This screwed me for hours as the SPI just kept falling over above 1mhz.
Not enough drive power for the circuit capacitance etc.

Once I found the SLRCON register and cleared it the SPI bus would run happily at 10mhz with the PIC overclocked to 80mhz.
In the end I dropped back to 8mhz and 64mhz for the bus and pic respectively.

IIRC 10mhz SPI is the maximum for the MCP2515 running with an 8mhz crystal.

[retepsnikrep]

Anyone got anything else to add/share please??
I bared my feeble CAN soul, now it's your turn.

[Ioannis]

Very useful info that are posted in this thread, but I am afraid that CAN topic is not very popular!

Thanks anyway for your kindness to share your experience.

Ioannis

[HenrikOlsson]

I played with the MCP25625 (CAN controler and driver) using the SPI peripheral on the 18F57Q53 a while back (just looked, turns out it's 4 years ago now, bloody hell...).
My intention was to make a "universal" driver for it and it looks like I did get most of the way but then lost interest it (which is what usually happens) since I didn't really had a need and/or use for it at the time.

You could

#DEFINE CAN_OSCILLATOR 20
#DEFINE CAN_BITRATE 125000

And it would automatically set the CNF1-3 registers (to reasonable values) based on bitrate and oscillator speed. Low level read/write/modify register routines, medium level Load_Tx_Buffer & Read_Rx_Buffer routines and higher level like GetCANMessage seems to have been implemented. I need an actual project to finish it.