I have a distance sensor connected to an Arduino DUE and I want to wire its output to an Arduino UNO.

In Arduino DUE, after calculating the distance, I convert a range of distances (0-10cm) to Volts (0-5V), then I map these to 0-255 values and I do AnalogWrite at the DAC pin.

In Arduino UNO, I AnalogRead from an analog pin (A0) which is connected with a jumpwire to the DAC pin of Arduino DUE. I was expecting to get values between 0 (when the distance is 0 cm) and 1023 (when the distance is 10 cm). But instead I get a weird and unstable range between 100 and 548.

The two Arduinos are connected with a jumpwire between grounds and a jumpwire between DAC and A0.

What am I doing wrong? I thought I had understood how to do this, but apparently not :)

Thank you for your help and time in advance!


  • 1
    why do you want to do this? Due is 3.3 V and Uno ADC reads 1023 at 5 V – Juraj Oct 21 '20 at 16:26
  • I'm not too sure what you're end goal is but it sounds like your using this as a means of communication. If that's the case, use a level shifter and communicate via UART through the arduino. Here's a link for the level shifter adafruit.com/product/757 – bunker89320 Oct 21 '20 at 17:35
  • As said by @Juraj it is 3.3V, so it is normal to have a value from 0 to 550. Add a 1k resistor to ground if you want a better and stable output. Isn't there a better way to transmit the value? You will never be able to transmit the real value if you convert it to an analog signal. – Adriano Oct 21 '20 at 19:32
  • Thank you very much guys! The reason I want to do this, is that the Arduino UNO is already part of a larger system that I cannot modify. This Arduino UNO normally reads the analog signal from a potentiometer. I need to replace this potentiometer with a distance sensor. So I bought the ultrasonic HS sensor and I reasoned that I could do it through an Arduino DUE that does AnalogWrite to the Arduino UNO that does its AnalogRead. Do you think I could do it in a smarter way? I am not super good with these so any help/suggestions are greatly appreciated! – Konstantina Kilteni Oct 22 '20 at 5:17

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