CMWX1ZZABZ with STM32CubeExpansion_SFOX_V1.1.0 blocks on TX_START unless PA2 and PA3 are physically pulled up and configured as LPUART
Hi,
I have tested a B-L072Z-LRWAN1 board with the default Sgfx_push_button application included in STM32CubeExpansion_SFOX_V1.1.0 folder. So far so good, everything was working as expected.
I've designed and built a custom board, following the requirements for using the CMWX1ZZABZ with Sigfox. (especially connecting SX1276_DIO4 to PA5). Whith the same Sgfx_push_button application, the application is blocking on TX_START (shown on the serial terminal with DEBUG active).
B-L072Z-LRWAN1 is using PA2 and PA3 as STLINK_TX/STLINK_RX while on my custom board PA2 and PA3 are not in use. I've disconnected PA2 and PA3 form STLINK on B-L072Z-LRWAN1 (opening SB28 and SB29) and I was able to reproduce the problem, same application blocking on the TX_START as on my custom board.
Working around the problem, I've tied PA2 and PA3 to +3V3 and the transmission occurred every time when triggered as should. However, I needed to see on the serial console what's going so I reconfigured LPUART1 to use PA14 and PA13. Once this done, the problem came back, application blocking on TX_START.
I've tried to configure PA2/PA3 as OUTPUT_PP PULLUP (and toggled UP) and as ADC, the only configuration that seems to work being configured as LPUART and physically pulled up.
I was not able to find in the documentation and source code anything meaningful related to this.
Was somebody coming across the same problem? Any help would be appreciated.
Thank you,
Bogdan Paduraru
