4 Replies Latest reply on Apr 21, 2016 1:53 PM by nemrod

    Disable internal pull up resistors on SDA and SCL lines

    NickMC

      Hello,

       

      I want to try to disable the internal pull-up on the Edison because they are pulling the voltage up to 5v when my sensors run at 3v3. Currently I am using external pull ups on the SDA and SCL lines and this is creating a voltage divider on the lines, giving me 4.1v on the SDA and SCL lines. I want to see if by disabling the 5v internal pull ups, if i can still read the digital data on the I2C bus and if this has any effect on the ADC values I am reading off the analog inputs A1 and A2.

       

      I have tried changing the J9 jumper to 3v3 to pull up the SDA and SCL lines to 3v3 which works well for my digital sensors but it ruins the ADC conversion on the inputs A1 and A2 because im using a sensor that produces a 0 to 5v output signal and one that has a 300mv to 1.1v output range.

       

      This example here shows How to disable internal Arduino ATMEGA pullups on SDA and SCL with I2C bus | Varesano.net  and all i want to do is be able to do this on the Edison.

       

      Can it be done from the Ardiuno IDE?

       

      Regards,

      Nick