5 Replies Latest reply on Feb 26, 2015 2:37 PM by KurtE

    Can't program SPI SCK higher than 4MHz Edison mini breakout board

    dexterloqueras

      Hi,

      I am trying to connect a MCP4922 DAC to the Edison mini breakout board. I am using python mraa library and yocto image. There is a function under mraa.Spi class that will set up the SCK frequency as you want, but it seems that is not working since I am looking to set the SPI SCK to 20MHz as is needed by this DAC.

       

      import mraa as m

       

      dev = m.Spi(0)

      dev.frequency(20000000)

      dev.mode(0)

      dev.bitPerWord(16)

      while True:

        txbuf = bytearray(2)

        txbuf[0] = 0b00000000

        txbuf[1] = 0b01110101

        dev.write(txbuf)

       

      Using a scope I am seeing that SCK is 6.2MHz. For some reason using this code I am not able to see any voltage at the DAC output so I am thinking it could be the SPI SCK speed.

       

      I will really appreciate your help. Thanks

       

      Scope.png