[ARM] HSE STM32 crashes during GSM operation

Faced with such a problem. CSS (clock security system) is enabled for the STM32F205RET6, when an HSE fails, an NMI interrupt is generated. I register the failure fact in BKPSRAM STM32 and do a reset. The board works with Ethernet and GSM. Only when working with GSM (SIM800C) sometimes I fix a non-zero CSS hit counter.

The GSM antenna is like that. With an antenna on the cable 2 m is better, but it should work with the antenna nearby.

It was not possible to achieve CSS on the table, which I just didn’t do. I tried to work without an antenna - SIM800C works without an antenna, all the base stations are nearby. I connected an equivalent in the form of 4 resistors 1206 of 200 Ohms instead of an antenna, also works without problems as well as without an antenna. I tested the power supply (ST1S14) with an equivalent load of 2A - no problem.

On the board - GSM in the form of a module. GSM power and ground are duplicated by the 4th legs of the PLS connector. Quartz STM32 make in accordance with all rules - it connects to the ground STM32 separately from the backward earth, there is a shielding loop around the quartz chains.

Hi,

There is no solid GND plane on the microcontroller board. Then HF nearby ...malfunction is quite expectable.

--> Use one layer for GND only. No cuts, no other traces. Then try again.


Klaus

Expect field strengths up to 1000 V/m near a transmitting GSM antenna. The PCB is acting as part of the monopole antenna, RF currents are injected in the GSM module board and conducted to the processor board.

If you don't want to redesign the processor board, you can try with a metal shield around the board soldered to antenna jack ground. It might be also possible to reduce the susceptibility with a few additional supply bypass capacitors and small capacitors at sensitive lines, e.g. reset input. Obviously, you need a continuous ground at least around the processor to connect it.