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STM32L031G6U6 only works in debug debug mode

Question asked by morrison.simon on Jun 12, 2018

Custom PCB using an STM32L031G6U6 (as a slave co-processor to a BLE module, to drive a graphics LCD display). We started with a Nucleo then migrated the project to a custom PCB which implements SWD directly and the program runs okay when debugging via an adapter lead to my Segger J-Link under the control of IAR Embedded Workbench for ARM 8.22.2. The STM is configured using STM32CubeMX 4.25.1. Both of these projects are contained in the attached zip file.


Previously, I have 4-5 years experience with STM32F205 and the IAR (and previously Atollic) IDEs, but this is my first project using STMCube.


1) Anyway, my progran runs fine on the STD debugger, but when I detach the SWD port the program does not start. The rise time of my DC PSU is 2ms. I have an external 100nF capacitor on NRST. I have tried putting 100K pull-up resistors on SWDIO and SWCLK but this made no difference. As far as I can tell, the program just does not start. Please can I have your ideas?

2) Can anybody tell me how to set up the level of POR from either STMCube or IAR?


Thanks in advance, Simon