ADC Sampling Principle

power_wong921

ADC Sampling Principle [Copy link]

 

Hello everyone! Recently I saw an ADC sampling code written by PIC18F45K80 series microcontroller. The main code is as follows:
ADC is 12-bit precision, one channel is sampled 64 times, and then the average value is calculated. However, I don’t understand the sentence V_SampleSum += (V_SampleData >> 4); V_SampleSum is the accumulated 64 AD sampling values. Why not just use V_SampleSum += ADC_SampleData;

I also hope that experts can explain the meaning of the code here, thank you!

#define        ShiftPoint            6
uint          V_SampleData = 0;                         //临时变量
ulong          V_SampleSum  = 0;                         //输出电压采集值累加
volatile    uint          V_SampleValueFilt = 0;                         //输出电压滤波采集值
 
ADC_SampleData = (uint)(((ADRESH&0x0F)<<8) + ADRESL);
 
case    S_54V:                    //54V采样电压通道
            {
                V_SampleData = ADC_SampleData + (V_SampleData - (V_SampleData >> 4));
                if(SampleFlag == 0)
                    V_SampleSum    += (V_SampleData >> 4);
                                        
                break;
            }
 
V_SampleValueFilt = (V_SampleSum>>(ShiftPoint));//求最终的ADC平均值

lugl4313820

What is the sampling speed? Will the accuracy be much higher if the sampling is done in this way?

power_wong921

Hello! The system clock FOSC is a crystal oscillator with a frequency of 11.0592, then multiplied by 4. The AD conversion clock is FOSC/64, and the AD result acquisition time TAD = 6

power_wong921

lugl4313820 posted on 2024-3-4 10:02 What is the sampling speed? Will the accuracy be much higher if the sampling is done in this way?

An interrupt will be generated after the AD conversion is completed