Unable to enable internal pullDown in some pins like PB_12 and PA_10

LPWAN Modules / EVBs RAK3172
1

I’m using Mbed OS and trying to enable an interrupt on pin PB_12 for a reed switch.

#define reed_pin PB_12

InterruptIn reed(reed_pin,PullDown);

I’ve configured the interrupt pin to use internal pullDown, but the pin’s voltage seems to be floating for PB_12, always VCC for PA_10, but curiously, it works property with PA_0.

¿Is there something connected to pins PB_12 or PA_10 in RAK3172 that prevent the use of internal pulldown?

Thanks

2

Hello @jfmateos

Are you sure it is PB_12 floating and PA_10 VCC and not the other way around?

PB12 has a pullup to VCC inside the module. For PA_10, I am not sure, it is a combined ADC/DAC/GPIO pin. Could be that it cannot be programmed with internal pullup because of the ADC/DAC functionality

3

Thanks @beegee
I will recheck it tomorrow.
Where could I find the schematic to see that pullup resistor on PB12?

Kins regards from Madrid

4

Schematics of our WisDuo modules are not made public.

I am still talking with R&D about the other pin, PA_10.

5

Thank you very much @beegee

My problem is that I am designing a custom board based on RAK3172 (with no additional microcontroller) and I need to connect digital/analog/interrupt inputs to it.

imagen
imagen1280×720 96.4 KB

I have tested all the available pins and none of them gives the expected value for all internal pullup/pulldown configurations (except perhaps PB_3 that has an odd 0.11V as interrupt pulldown, and PA_0 that cannot be properly tested because I already have circuitery connected to it).

imagen

The PB_12 results are consistent with the PullUp resistor you commented before.
I don’t need the schematic, just need to know what other connections have these pins inside the Rak3172 module.

Kind regards

6

More information

PA_10 didn’t get the pullDown configuration with InterruptIn using the Mbed example (mbed-os-example-lorawan) as shown in the table above, but it works with a simpler program (see below), so there must be something in the mbed example inpacting that pin

#include "mbed.h"


InterruptIn reed(PA_10,PullDown);

 
int main() {
    while(true){
        
        ThisThread::sleep_for(1s);
        
    }  
}
7

The problem with PA_10 not entering PullDown configuration in InterruptIn was this line:
imagen
After removing it, the Interrupt is working properly.
I will try to further investigate interrupt behaviour in other pins.

8

For the IO pins of RAK3172, except PB12, all pins of the stamp module are directly connected to the STM32WL5 chip, no pull-ups or pull-downs attached to them.

I have no experience with Mbed OS, so I do not know how it does the setup of the GPIO’s.

9

Thank you very much @beegee
That’s a very valuable information.
Kind regards.