[参考译文] ADS1299：nRF52832电路板上的 SPI 通信和数据不稳定性问题(异常值)疑难解答

void loop(){
  if (is_running) {
    //is data ready?      
    while(!(ADSManager.isDataAvailable())){            // watch the DRDY pin
      delayMicroseconds(10);
    }
    unsigned long start_micros = micros();
  
    //get the data
    // analogVal = analogRead(PIN_ANALOGINPUT);   // get analog value
    ADSManager.updateChannelData();            // update the channelData array 
    sampleCounter++;                           // increment my sample counter
    
    //Apply  filers to the data
    if (useFilters) applyFilters();
    ADSManager.printChannelDataAsText(MAX_N_CHANNELS,sampleCounter);  //print all channels, whether active or not
  }

} // end of loop

void ADS1299::updateChannelData(){
	byte inByte;
	int nchan=8;  //assume 8 channel.  If needed, it automatically changes to 16 automatically in a later block.
	digitalWrite(CS, LOW);				//  open SPI
	
	// READ CHANNEL DATA FROM FIRST ADS IN DAISY LINE
	for(int i=0; i<3; i++){			//  read 3 byte status register from ADS 1 (1100+LOFF_STATP+LOFF_STATN+GPIO[7:4])
		inByte = transfer(0x00);
		stat_1 = (stat_1<<8) | inByte;				
	}
	
	for(int i = 0; i<8; i++){
		for(int j=0; j<3; j++){		//  read 24 bits of channel data from 1st ADS in 8 3 byte chunks
			inByte = transfer(0x00);
			channelData[i] = (channelData[i]<<8) | inByte;
		}
	}
	
	digitalWrite(CS, HIGH);				//  close SPI
	
	//reformat the numbers
	for(int i=0; i<nchan; i++){			// convert 3 byte 2's compliment to 4 byte 2's compliment	
		if(bitRead(channelData[i],23) == 1){	
			channelData[i] |= 0xFF000000;
		}else{
			channelData[i] &= 0x00FFFFFF;
		}
	}
}

#include "ADS1299.h"

void ADS1299::initialize(int _DRDY, int _RST, int _CS, int _FREQ, boolean _isDaisy){
	isDaisy = _isDaisy;
	DRDY = _DRDY;
	CS = _CS;
	int FREQ = _FREQ;
	int RST = _RST;
	
	delay(250);				// recommended power up sequence requiers Tpor (~32mS)	
	pinMode(RST,OUTPUT);
	digitalWrite(RST,LOW);
	delayMicroseconds(4);	// toggle reset pin
	digitalWrite(RST,HIGH);
	delayMicroseconds(20);	// recommended to wait 18 Tclk before using device (~8uS);
	

    // **** ----- SPI Setup ----- **** //
    
    SPI.begin();
    SPI.setBitOrder(MSBFIRST);
    SPI.setDataMode(SPI_MODE1); // clock polarity = 0; clock phase = 1 (pg. 8)
    
    switch (FREQ){
        case 8:
            SPI.setClockDivider(SPI_CLOCK_DIV8);
            break;
        case 4:
            SPI.setClockDivider(SPI_CLOCK_DIV16);
            break;
        case 2:
            SPI.setClockDivider(SPI_CLOCK_DIV32);
            break;
        case 1:
            SPI.setClockDivider(SPI_CLOCK_DIV64);
            break;
        default:
            break;
    }
    
    // **** ----- End of SPI Setup ----- **** //
    
    // initalize the data ready chip select and reset pins:
    pinMode(DRDY, INPUT);
    pinMode(CS, OUTPUT);
    
    digitalWrite(CS,HIGH); 	
	digitalWrite(RST,HIGH);
}


//SPI communication methods
byte ADS1299::transfer(byte _data) {
	return SPI.transfer(_data);
}