Nordic Tech (Customer) asked a question.
Hi all,
I have run into an issue trying to read an analog signal from a load cell (FX293X-100A-0050-L). The load cell outputs an analog signal from 0.5-4.5V. The load cells require a 5V supply which I am generating using a buck converter. Ive tested these using the default Aref up to 3.3V and they work just fine. Today I tried applying 5V to the Aref pin and it seems to mess up the Vcc voltage on the P1AM. Before I connect 5V to Aref I measure 3.3V on the Vcc pin, and as soon as I apply 5V to the Aref the Vcc voltage jumps to ~4V. I did this test with and without my code and I get the same result.
I found this in the arduino documentation (https://docs.arduino.cc/language-reference/en/functions/analog-io/analogReference/) and have added a analogReference(AR_EXTERNAL); line to my code before I set the pinMode on any analog pins.
I was wondering if there is any documentation related to using external analog reference voltages. It seems like I can use Aref for voltages <3.3V but not greater than. Can anyone confirm this?
Any help would be greatly appreciated!
Thanks!
The aref pin will be limited to 3.3V(*technically* 3.6V) on the P1AM-100. It's a limitation of the SAMD21 chip in relation to VCC. Below is a snippet with the absolute max on any pin from the microcontroller datasheet.
Thank you for the reply!
I will likely reduce the voltage signal from the load cells using a voltage divider, or find a suitable ADC.