Make the RTC count every 1 ms

RE: Make the RTC count every 1 ms

Wojtek — Mon, 23 May 2016 12:01:04 GMT

You can check this topic. I don't see any better solutions...

RE: Make the RTC count every 1 ms

Revo — Mon, 23 May 2016 11:56:21 GMT

I will do it but currently i don't have an oscilloscope (tomorrow i will check); but supposing that it won't work, aren't there other solutions?

RE: Make the RTC count every 1 ms

Wojtek — Mon, 23 May 2016 11:54:11 GMT

You have to check it, you can do it way i proposed in comment above.

RE: Make the RTC count every 1 ms

Revo — Mon, 23 May 2016 11:36:55 GMT

So defintely i cannot sample a signal with a nrf51822 at 1 kHz?

RE: Make the RTC count every 1 ms

Wojtek — Mon, 23 May 2016 11:34:12 GMT

If you have oscilloscope you can set some pin in app_timer handler and then clear it in ADC irq handler. you will see that way if your app_timer and adc irq interval is 1kHz or not. I bet it is not.

RE: Make the RTC count every 1 ms

Revo — Mon, 23 May 2016 11:21:58 GMT

As you can probably see i still fill up a buffer of 20 bytes and then send it, you suggest to move it out from the IRQ handler function or what? Is really no way to reach 1kHz for sure maybe changing the clock source or what?

RE: Make the RTC count every 1 ms

Wojtek — Mon, 23 May 2016 10:51:47 GMT

Ok, i don't think you are able to keep 1kHz like that. You are using app_timer with scheduler, and later update BLE characteristics from IRQ - i don't think this is good idea. What I could suggest is to buffer more than one ADC sample, (ex. buffer up to 20 bytes), and then send it, and in the meantime just take samples (and nothing more, to have IRQ as short as possible). And maybe you have to get rid of app timer or at least move it out from scheduler, so it could really keep 1khZ. But still i am not sure you will have your frequency - softdevice has quite large timing overhead...

RE: Make the RTC count every 1 ms

Revo — Mon, 23 May 2016 10:42:16 GMT

I know, i post the main so you can see from yourself all the infos. However i take the result always in the IRQ handler!

RE: Make the RTC count every 1 ms

Wojtek — Mon, 23 May 2016 10:38:55 GMT

and when you take the result...? It is really hard to tell something without knowing your program flow. Or if you are using SD or something...

RE: Make the RTC count every 1 ms

Revo — Mon, 23 May 2016 10:37:47 GMT

Yes, i put TASK_START=1 in the timeout handler, and stop it in the IRQ of the ADC conversion complete.

RE: Make the RTC count every 1 ms

Wojtek — Mon, 23 May 2016 10:34:48 GMT

By activate you mean task START? or task start and waiting for sample to finish?

RE: Make the RTC count every 1 ms

Revo — Mon, 23 May 2016 10:33:08 GMT

By IRQ, i activate the ADC in the RTC interrupt!

RE: Make the RTC count every 1 ms

Wojtek — Mon, 23 May 2016 10:32:02 GMT

how do you sample ADC? blocking mode or by IRQ?