SPI does not work without debugger or RTT Viewer

[Moshe Baker]

Hi,

Our Nordic app is doing BLE<->SPI communication.

All works fine when running in debug mode with SEGGER IDE.

Once we run without the debugger running, the SPI transmits all sorts of garbage. there is no pattern, it is not a bit shift or byte shift

Strangely, also running RTT Viewer "fixes" the problem.

What can explain this???

We tried different SPI modes and configuration. it makes no difference.

Please respond ASAP. This is a killer of for us!.

Thanks,

Moshe

[Kenneth]

So there is no change in firmware here, only a difference caused by debugger is connected or not? 

If it's only caused by debugger is attached or not (or RTT viewer is running), then I would look at the hardware (e.g. check that proper ground connection between devices in the system and also check that vdd is connected (or very close to same level (e.g. ~100mV)) between devices that are connected in the system). 

[Shahar]

The issue seems to be related to sd_power_mode_set.

Following https://devzone.nordicsemi.com/f/nordic-q-a/34965/spis-data-shifting/134368

sd_power_mode_set(NRF_POWER_MODE_CONSTLAT);

 

Seems to have resolved the issue