Roborio RS-232 port issue

[sanelss]

Originally Posted by jman4747

Yes RS-232 is +15V to to -3V. The arduino is TTL UART at 5V. Conjecture, use the UART on the MXP port. Also note that the dedicated I2c, MXP I2c pins, and MXP UART are all at 3.3V. Using a 3.3 volt arduino or Bi-directional I2c safe level shiftier is necessary for I2c.

What I did was use software serial which supports inverted logic so I don't need to change pins or use any additional hardware on the arduino. the port can handle higher voltage so i just shove the tx line from arduino to the rx on roborio, i only care about one way communication so I don't need to worry about the -V output of the roborio. the i2c device we use has open collector output and I just pulled it up to the 3.3V rail so no problems on that end.

I just got it working as expected though a bit annoying to figure out!