Counter using timer

RE: Counter using timer

Einar Thorsrud — Tue, 07 Dec 2021 11:09:05 GMT

Hi,

There is an example of using LPCOMP with a timer and PPI in his thread. Perhaps that is the best one to look at. For the COMP you could look at the implementation in <SDK>\components\libraries\csense_drv\nrf_drv_csense.c. Perhaps it would also be good to look at and understand the PPI example. This just use two timers, but demonstrates well how PPI works.

RE: Counter using timer

Judge — Tue, 07 Dec 2021 01:48:48 GMT

Hi,

can you give me a sample of code using all 3 of them? (PPI, timer, and comp) I'm using nrf mesh SDK 16

Best regards

RE: Counter using timer

Einar Thorsrud — Mon, 06 Dec 2021 13:52:01 GMT

Hi,

PPI does not contribute to increased current consumption. In practice, it should lead to a small reduction in over all energy use as the operation is as efficient as possible, and without using the CPU more than necessary.

RE: Counter using timer

Judge — Sat, 04 Dec 2021 07:11:23 GMT

Hi,

Great for your suggestion. But I am having a question when using PPI what will be the current consumed? Since our device has to optimize the power level in the best way, I want to know this

RE: Counter using timer

Einar Thorsrud — Fri, 03 Dec 2021 12:58:08 GMT

Hi,

There are a few potential error sources here:

You are measuring an analog input signal by reading it as a digital input. This will be inaccurate as there is a significant undefined region (see GPIO Electrical Specification). You should use the comparator for such tasks.
You have a while loop where you read. If there is an interrupt in between here that could cause additional delay. You should solve this using PPI.

As you see, the proper way to do this, which would solve both these issues is to use the comparator to get an event when the voltage passes a threshold, and use PPI to capture the timer when that happens. This way this will happen all in HW, and you can read the value later when the CPU has time. Any interrupts at a bad time will not affect the measurements.