Extra pin monitoring


We are trying to monitor the ON_Sleep (DIO9) pin of an NB-IoT cellular module made by Digi. We have wired this pin to processor’s A9 pin declared as an input pin.

We expected to be able to assert the cellular module’s pin state (0 / 3,3V), but this does not seem to work; furthermore the whole operation of the cellular module is affected.

Are we doing something wrong?

Hi Darius,

If I’m correct pin 9 is the sleep pin on the XBee.

Based on a quick glance to our schematics it seems that this pin is not called A9 on the autonomo.

I think it is actually on A13, let me know if that pin works.


Hello Thom,

Our purpose is to get a confirmation when the XBee module goes to sleep, and in this respect we try to follow the ON /SLEEP/DIO9 which is PIN 13 on the Digi documentation which you have referred to, which does not seem to be connected to the Autonomo pins. We do use A13 pin of the Autonomo to send the XBee to sleep and wake it up.
On the other hand, we are trying to check XBee’s pin 13, which we have connected to Autonomo’s pin A9, and we noticed that this is affecting the serial communication between the XBee and Autonomo.

Hi Darius,

Clear, seems I misunderstood there!
I’ll need you to describe what exactly " this is affecting the serial communication between the XBee and Autonomo." means. Could you show me some code snippets? Perhaps some imagery would be helpful here too.


Hi Thom,

In our application, Automomo and XBee are ‘talking’ on the serial port, and there were times when the transmission or reception did not work at all, or messages were scrambled (containing non-ASCII characters).

What is even stranger si that if we connected first the USB cable (PC to Autonomo) and then the battery, they started working together fine, which makes us think that there would be some resistor/capacitor needed to be connected between the Autonomo and XBee pins?

Hi @darius.popa ,

Sounds like you have some blocking code in your setup()
Do you have somewhere: While(!SerialUSB); ?
Or can you share your setup code so we can have a look why this might happen?

Bes regards,

Dear Jan and Thom,

We have just reached a conclusion after we did further investigation into the matter: there is a hardware issue with that specific Autonomo board. We could see other weird things happening, and then we changed the board with another Autonomo and everything worked as expected!
A good reason to buy more! :slight_smile:
Thank you once again!
Best Regards,