Skip to content
    • Welcome to the Linux Foundation Forum!

    Why would I get two write_raw() calls in an IIO driver?

    Posts: 2
    in Drivers

    I'm working on an IIO DAC driver for a LTC1669 single channel DAC. I have the driver mostly working but have an issue when I write to the out_voltage_raw sysfs file. On an oscilloscope I see the output of the DAC briefly go up then it goes back to 0V.

    /sys/bus/iio/devices/iio:device1# echo 512 > out_voltage_raw
    ltc1669_write_raw: chan:0 val:512 val2:0 mask:0
    ltc1669_write: 512 - 00:00:02
    ltc1669_write_raw: chan:0 val:0 val2:0 mask:0
    ltc1669_write: 0 - 00:00:00

    Any ideas why I'm seeing the second write?

    Thanks

    Answers

    • Posts: 2

      Never mind. I figured it out.

      My I2C write function used by (*write_raw) was returning the result if i2c_master_send(). I assumed that return would be 0 on success, it actually returns the number of bytes written.

      Fixed that and now the DAC is set properly.

    • Posts: 2

      Thank you for the post @bigguiness
      I have a similar issue here. Could you please elaborate more on this?

    Welcome!

    It looks like you're new here. Sign in or register to get started.
    Sign In

    Welcome!

    It looks like you're new here. Sign in or register to get started.
    Sign In

    Quick Links

    Categories

    Upcoming Training