GPIO Pins for external peripherals

Issue: Connecting External Peripherals

Setup: To connect LED to RAK5010

Details: I want to use an ext LED to indicate low battery status. However, i am not sure which IO pin I can connect to? From the J12 pinout, there are IO 1-4. But from the schematic, it shows that they are connected to the SIM module. Can someone help?

The IO 1-4 are not connected to SIM module. They are connected to a logic-level shifter then to NRF52840. Here’s the schematic connection. They are named NRF_IO1 to NRF_IO4.


NRF_IO1 - P0.19
NRF_IO2 - P0.20
NRF_IO3 - P1.02
NRF_IO4 - P1.01

Full schematic can be downloaded on this link

Hi Carl,

What is the pin assignment? In number format? Eg. Is pin 20, IO2?
I have tried to connect an LED to the pin 20 and done a simple test, but LED still doesnt light up, as the voltage at pin 20 is still read as 0V.

 pinMode(20, OUTPUT);

LED is fine, verified connecting between gnd and Vref.

Pin 19 or 20 should work. What voltage did you put on EXT_VREF?

Hi Carl,

I missed that part. Vref is not connected to anything at this moment. Can i connect Vbat to Vref ?I do not want to connect any other source to the RAK to make it compact.

Vbat is ok. Doing that, the high voltage level of your IO pin will be the Vbat level too.

Hi Carl,

Thanks. Will try that.