Member Since: March 22, 2013

Country: United States

  • After banging my head against the wall trying to get this board to work with the Arduino Mega 2560, I finally figured it out. As was mentioned previously, you have to wire the SPI bus pins 10-13 of the shield to 50-53 of the Mega 2560 as follows:

    • Mega CAN bus shield
    • 51 11 (SPI MOSI)
    • 50 12 (SPI MISO)
    • 52 13 (SPI SCK)
    • 53 10 (SPI CS)

    But, the final trick to get the SKPang software to work properly was to modify the port assignments in file “defaults.h” as follows:

    // Atmega 168/328 pin mapping
    //#define   P_MOSI      B,3 // pin 11
    //#define   P_MISO      B,4 // pin 12
    //#define   P_SCK       B,5 // pin 13
    //#define   MCP2515_CS  B,2 // pin 10
    //#define   MCP2515_INT D,2 // pin 2
    //#define   LED2_HIGH   B,0 // pin 8
    //#define   LED2_LOW    B,0 // pin 8
    // Pins remapped to Arduino Mega 2560
    #define P_MOSI          B,2 // pin 51
    #define P_MISO          B,3 // pin 50
    #define P_SCK           B,1 // pin 52
    #define MCP2515_CS      B,0 // pin 53
    #define MCP2515_INT     E,4 // pin 2
    #define LED2_HIGH       H,5 // pin 8
    #define LED2_LOW        H,5 // pin 8

    I did some reading here: It discusses the advantage of better speed of controlling I/O pins by writing directly to the ports, but the disadvantage is that it is not a portable design to other processor pin maps. Yup.

    The 2 pin maps I found here, and corrected the mappings: (this is what the shield was designed to run with)

    This works! Hallelujah!

  • Your info implies there might be more than one “standard” for the pinout of the DB-9 connector. If you look at the pinout dwg for the Sparkfun cable, it agrees with the board schematic:

  • I am just getting started using this shield with the Mega 2560 - any wiring connectivity help would be appreciated. I’ve seen some discussion about the use of different pins and wiring some pins to other locations, and I’m a noob, so a wiring diagram of what actually works would be great.

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