Support for MCP2515 with 12MHz oscillator

[carsondarling]

I was recently attempting to use a CAN board designed for a Raspi (Waveshare's CAN Hat) with this library, but it has a 12MHz crystal attached to the MCP2515. I was able to modify MCP2515.cpp to support the 12MHz oscillator for my use case below. Is there interest in me putting together a pull request for full 12MHz support in this library?

diff --git a/src/MCP2515.cpp b/src/MCP2515.cpp
index aa46051..e6afd08 100644
--- a/src/MCP2515.cpp
+++ b/src/MCP2515.cpp
@@ -103,6 +103,8 @@ int MCP2515Class::begin(long baudRate)
     {  (long)8E6,   (long)10E3, { 0x0f, 0xbf, 0x07 } },
     {  (long)8E6,    (long)5E3, { 0x1f, 0xbf, 0x07 } },
 
+    { (long)12E6,  (long)500E3, { 0x00, 0xa2, 0x02 } },
+
     { (long)16E6, (long)1000E3, { 0x00, 0xd0, 0x82 } },
     { (long)16E6,  (long)500E3, { 0x00, 0xf0, 0x86 } },
     { (long)16E6,  (long)250E3, { 0x41, 0xf1, 0x85 } },

[hellmutbrudny]

Hi. I found this one looking for a solution for the same problem. But... I wanted to run my CAN HAT with 250kbps (this is a standard in my network). How did you calculated your values for 500kbps?

[carsondarling]

I used the datasheet's description of the CNF registers (section starts on page 39). I know Kvaser has a calculator , though I haven't used it.

[carsondarling]

Looking at the Kvaser calculator, it seems like you could use something like this:

+    { (long)12E6,  (long)250E3, { 0x01, 0x9b, 0x02 } },

(fair warning: this is totally untested, YMMV, etc)

[hellmutbrudny]

Your values work. Thanks A LOT!

[magicsmoke]

Yeah, this could defo be added to the library.

[carsondarling]

For what it's worth, I've since started using timurrrr/arduino-CAN (a fork of this library) since it appears that @sandeepmistry isn't updating this version.