High current when advertising with RTOS

RE: High current when advertising with RTOS

robert — Fri, 15 Jun 2018 17:59:41 GMT

I found the solution. Yes, it is caused by FPU interrupt. After reading errata #87, I guess SoftDevice enables FPU IRQ so that FPU interrupt keep happening due to this errata. When the patch code is placed inside idleTask(), it might be interrupted by FPU interrupt. I think it should be better to be placed in the FPU ISR.

So, I add a FPU ISR and put the patch code inside the ISR. It works very well. The figure below shows ADC sampling at 100Hz with three peaks indicate BLE advertising timing.

I think it should be useful to add this workaround in nRF52832 revision errata doc.

RE: High current when advertising with RTOS

robert — Fri, 15 Jun 2018 16:40:19 GMT

No luck and even worse. The CPU is completely halted with the patch code. The CPU is no more working and gets reset by watchdog. (I have configured watchdog timeout with 3 seconds)

RE: High current when advertising with RTOS

Håkon Alseth — Fri, 15 Jun 2018 10:49:28 GMT

Hi,

Most of your scenarios show a base current of ~3.5 mA, which is very high.

It could be the FPU that is waking up the CPU (errata #87). Could you try adding this prior to entering sleep?

#if (__FPU_USED == 1)
 __set_FPSCR(__get_FPSCR() & ~(0x0000009F)); 
 (void) __get_FPSCR();
 NVIC_ClearPendingIRQ(FPU_IRQn);
#endif
 my_sleep_function();

Best regards,

Håkon