RE: AC (240V) current measurement using a CT with NRF52832

bivay — Wed, 25 Sep 2019 12:49:56 GMT

Thanks

RE: AC (240V) current measurement using a CT with NRF52832

haakonsh — Wed, 25 Sep 2019 12:25:52 GMT

Yes, with continuous sampling.

RE: AC (240V) current measurement using a CT with NRF52832

bivay — Wed, 25 Sep 2019 11:52:21 GMT

Can this will be achieved without requesting time slot or stopping BLE functionality.

RE: AC (240V) current measurement using a CT with NRF52832

haakonsh — Wed, 25 Sep 2019 08:01:17 GMT

[quote user=""]Which mode is suitable for it like single shot, or continuous mode?[/quote]

Continuous mode is best if you need accurate measurements(in time) and the easiest, but it has a bit more current consumption than single-shot.

Single shot on the other hand is at the mercy of the BLE stack who's got higher interrupt priority. One way to get around the interrupt priority is to use the Radio Timeslot API of the SoftDevice's Multiprotocol support to request a time slot where you have complete control of the MCU. For a 50Hz signal that requires 20ms of sampling + minor processing of the data.

To find the maximum and minimum value of an array you can use the ARM CMSIS DSP library's arm_max_f32 and arm_min_f32, or:

// Set min/max values for 10-bit precision
int16_t max_val = -1023;
int16_t min_val = 1023;

for(uint16_t i=0; i < SAMPLE_SIZE; i++)
{
    if(my_samples[i] > max_val)
    {
        max_val = my_samples[i];
    }
    else if(my_samples[i] < min_val)
    {
        min_val = my_samples[i];
    }
}