I am looking over the connections between the CAN Shield V2.0 and an Arduino Mega2560 and seek some clarification.
The Shield PCB schematic shows the SPI signals MOSI, MISO and SCK connected to the PB connector, pins 12,13 and 14 respectively. On the Arduino Mega2560 PCB, I believe this corresponds to pins 11,12 and 13 respectively (Arduino schematic JP6 pins 7,6 and 5). This in turn connects to pins 24, 25 and 26 on the ATMega2560 IC. These pins are assigned for general I/O or output compare functions.
The SPI pins on the ATMega2560 IC, pins 20, 21 and 22 are connected to 52, 51 and 50 respectively (Arduino schematic 36 way connector XIO pins 33,32 and 31).
At first glance, the shield SPI pins do not connect to the SPI interface on the ATMega2560. The alternative connections are via the ISCP pins on the shield, however, the female connector on the bottom will not mate with the female connector on the Arduino PCB.
This leads me to the following queries regarding the Arduino Mega2560 module.
- Is the SPI being bit bashed at the PB connector pins on the shield.
- Is the ATMega2560 IC SPI port connected to the shield via some means which I have missed?