B-L072-ZLRWAN1 not working while on battery

Hagen Wittlich · ‎2018-06-03

Posted on June 03, 2018 at 18:46

Dear STM32 Community,

I have a B-L072-ZLRWAN1 that I have programmed using arduino and the libraries from

https://github.com/GrumpyOldPizza/ArduinoCore-stm32l0

. I use the board to connect to The Things Network and it works, as long as it is connected to my PC. However, if I try to power the board via the battery compartment, only LED 7 lights up but no connection to TTN happens. Any ideas what the reason could be? I am new to this board and couldn't find a solution in the specs. Thank you for your help and time!

T J · ‎2018-06-03

Posted on June 04, 2018 at 07:01

can you check the batteries voltage ? are they new or old batteries ?

did you check the reference manual, what voltage do you need ?

sometimes the battery's terminals corrode, check with a meter the battery voltage on the pcb wire connection.

Hagen Wittlich · ‎2018-06-04

Posted on June 04, 2018 at 07:48

Hi TJ, thank you for your quick reply.

The batteries were all new when I first tested, my multimeter reads ~1.482 V for each. As mentioned before, LD 07 on the board is lit up, which supposedly means +5V power is present. I tested the 3V3 Pin and got ~3.3V, for the 5V pin I got a reading of ~4.2V.

The manual (

http://www.st.com/content/ccc/resource/technical/document/user_manual/group0/ac/62/15/c7/60/ac/4e/9c/DM00329995/files/DM00329995.pdf/jcr:content/translations/en.DM00329995.pdf

) states that 3 x AAA Batteries are to be used (p. 14).

There's nothing connected to the Board except for the standard antenna.

T J · ‎2018-06-04

Posted on June 04, 2018 at 07:55

as a transmitter, it will need some capacity in those batteries, not just surface voltage that is already low.

you are out of luck, I only have 2 AAA's here, can't test it easily here.

the boards works on 5V USB Yes ?

did you try new batteries ?

Hagen Wittlich · ‎2018-06-04

Posted on June 04, 2018 at 09:39

I will try brand new batteries later today , although I am fairly certain that the ones I used were fresh from a recently bought pack when I started testing.

- The board correctly connects to TTN when I plug it into my computer via USB.

- It does not connect at all using batteries.

- I haven't extensively tested using USB solely as power source (eg via power bank or wall outlet) , however so far that doesn't seem to work either.

I wonder if I have to change anything on the board, but my understanding of the electronics involved is limited. I appreciate your help greatly!

Hagen Wittlich · ‎2018-07-05

Posted on July 05, 2018 at 13:24

I got a great solution from someone on github. Simply put a jumper between NRST and 3V3, that suffices. The jumper needs to be removed if you don't want to power the board with batteries any longer.