My RAILUINO app required two modifications: 1. An extra (interrupt) wire between MCP2515 INT (pin12) and ATmega328P pin PD2 (pin32) 2. MCP2515 crystal should be 16MHz instead of 8 MHz. The MassiveButDynamic was willing to to both modifcations. Incredible good service!!! Now the CAN/ARDUINO works perfectly!!!