10 years, 5 months ago.

Sampling values from a 50Hz sine wave??

Hi

I have a program here which I am measuring a 50Hz sine wave using a Ticker which is calling my sampling function every 0.000625 seconds i.e period of waveform is 0.02 then dividing this by 32 to get 32 samples per waveform it requires to sample every 0.000625 seconds. The Ticker seems to be calling the ADC function correctly 32 times per period but when I try to read the values from the sampling of 4 waveforms they are wrong could somebody tell me why my below code isn't displaying the correct values?

Thanks

1. include "mbed.h" Serial pc(USBTX, USBRX);

**Global variables***

AnalogIn AinV(p16);

float ADC_Voltage_data;

float ADC_sampling_rate;

Ticker ADC_set;

float samples[128]; array to save 128 samples of data ie four waveforms of data

int ADC_Count;

DigitalOut sample_pulse(p17);

**Function prototype's

void ADC();

*Main Function**

int main() { sample_pulse=0;

ADC_Count=0;

ADC_set.attach(&ADC,0.000625); attach a ticker ADC-set to call ADC function at the sampling rate calculated to allow 32 samples per period

if (ADC_Count <128) {

}

for (int i=0;i<128;i++)

{

printf("%f\n\r", samples[ADC_Count]); }

}

*function to display analog input as voltage on LCD***

void ADC() {

sample_pulse=1;

ADC_Voltage_data=AinV*3.3; multiplyed by 3.3 to give the correct voltage reading

samples[ADC_Count]=ADC_Voltage_data; Save voltage reading within an array named ADC_count

sample_pulse=0;

}