RE: nRF52832 - how to reduce initialization time

John — Mon, 03 Apr 2017 09:19:20 GMT

Thanks Martin!

I solved the problem by using internal RC oscillator now. I used before external crystal oscillator. Now with internal RC oscillator, the start up time is now around 4 ms.

RE: nRF52832 - how to reduce initialization time

MartinBL — Mon, 03 Apr 2017 07:27:27 GMT

Hi,

I suspect you are using an external LF crystal? Those 252ms is most likely the time it takes for it to start when you initiate your Softdevice. Check out the start up time in the spec: 32.768 kHz crystal oscillator (LFXO).

What you can do is to use the internal RC oscillator when you first start your Softdevice, and then switch to the external oscillator at a less time critical point in time. The LFRC's startup time is much lower: 32.768 kHz RC oscillator (LFRC).

I once did some measurements of the LFXO startup time using an nRF51 DK kit. Normally the startup time was ~270ms, but when I put my finger on the crystal it increased to 500ms. So the startup time also seems very dependent on its environment. I guess my finger introduced some stray capacitance it didn't like. Large load capacitance means long startup time.

If you are using a bootloader that might also interfere with the start up time.