RAK 11720 Internal Reference Voltage 1.5V only

LPWAN Modules / EVBs RAK11720
#1

Hi team,

Me and the team have recently swapped out a RAK 3641 for the 11720 and did not realize that the only possible internal reference voltage was 1.5V for the ADC.

Due to this our battery monitoring circuit does not work and will only allow us to monitor voltages up to 2.5V. This is a massive issue for us as at the moment and we want to be 100% sure there is no alternatives in firmware that we can explore prior to making the required hardware changes.

We are using RUI3.

Cheers,
Tom.

#2

Hi @tom-b ,

I already relayed your inquiry to the RUI3 team. The person responsible on the RAK11720 should be able to confirm about alternatives if there is possible workaround via FW. I will get back to you soon when I got any information.

1 Like
#3

Hi @tom-b ,

I am not sure if will still be helpful to you but you can increase the reference voltage up to 2.0V.

This is the info I got from our engineer. You can use the RUI3 API - analogReference(AR_DEFAULT).

#4

Hi @carlrowan,

Thanks for that, I did actually find this when digging through the code and have opted for this. Unfortunately this is still too low given the voltage divider we currently have.

Assuming this is the only other option we are thinking we will need to swap the resistors on our voltage divider out manually for this first batch of PCBs.

If there are any other options that you know of let me know.

Cheers,