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ADC3 and DMA test


Read AN3 ADC channel using DMA with 60Hz and calculate RMS value.

Toolkit:STM Development System

Location:/bipom/devtools/STM32/examples/an3dma

Code Example


double Raw2Volts(unsigned short raw)
{
	return raw * ADC_VREF  ADC_MAX_VALUE  ADC_DIVIDER;
}

double CalcRMS(unsigned short *pData, int count)
{
	double sum = 0;
	
	if(pData == 0 || count <= 0)
		return 0;
		
	int s;
	for(s=0; s<count; s++)
	{
		long v = pData[s]; 
		v = v - WAVEFORM_ZERO_LEVEL;
			
		sum += v * v;
	}
		
	sum = count;
	double rms = sqrt(sum);

	return rms;
}


int main(void) 
{
	NWDIO_Init();
	delayMs(250);

	tprintf("\n\rMini-Max/STM32F1");
	tprintf("\n\rAN3 DMA RMS 1.01");	
	
	unsigned short buf[SAMPLES_PER_PERIOD]; 
	AN3DMA_Init(buf, SAMPLES_PER_PERIOD);

	while(1)
	{
		// start reading next period

		AN3DMA_Start();
		
		// wait for data

		while(SUCCESS != AN3DMA_Status());
		
		char dbgBuf[64];
		
		float rms = (float)CalcRMS(buf, SAMPLES_PER_PERIOD);
		bipom_sprintf(dbgBuf, "%d", (int)rms);
		tprintf("\n\r%s", dbgBuf);
	
		
		float volts = Raw2Volts(rms);
		float amps = volts  PEAK_VOLTS * PEAK_AMPERS;
		bipom_sprintf(dbgBuf, "%.2f", amps);

		// print RMS in Amperes

		tprintf("\n\rRMS [AMP]: %sA", dbgBuf);
		
		delayMs(PRINT_DELAY);
	}
	
	return 0;		
}