Sparkfun SAMD21 dev breakout issue

Projects General Guidance
1

My pressure sensor signal voltage to the arduino A0 pin is 75mV, or .015 of the 0-5V it puts out. The SAMD21 is 12 bit, so 4096 steps. .015*4095 = 61.4, but the reading is 26 or so. What am I missing??

Thanks!

Bill

2

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Here is the code and output.

3

Also, I am having to use the arduino MKR Zero drivers as whenever I load the Sparkfun samd21 dev breakout driver the board accepts programming, produces no error codes, but won't output any data.

4

Since the SAMD21 is a 3.3V ONLY processor, if a voltage > 3.3V was ever applied to the analog input, you may have damaged the ADC.

This thread shows how to get 16bit resolution using oversampling and averaging: Addressing SAM D21 ADC

More on getting the most out of the SAMD21 ADC: Reading analog values with the SAMD21's ADC - Stargirl (Thea) Flowers

5

Thanks. I'm such a noob. Only 75mV has ever been applied.

6

How do you know that?

You should NEVER connect a 5V device output to a 3.3V device input without taking precautions like using a voltage divider, a logic level shifter, etc. as the circumstances require.

7

Its a psia pressure sensor that has only been exposed to atmosphere. That's 75mV, period.

8

If you believe that, without checking for startup or shutdown transients, good luck.