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AD7856 Production
The AD7856 is a high speed, low power, 14-bit Analog-to-Digital Converter (ADC) that operates from a single 5 V power supply. The ADC powers up with a...
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AD7856 on Analog.com

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Problem with AD7856 SPI in Arduino... Help!!



		

			

									
					    psicko275
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jan 18, 2013 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi, I try using the AD7856 in Arduino Mega ADK board, I read the datasheet and I have programing under Mode 2, but the AD7856 don't answer me, I connect a oscilloscope to MOSI and MISO lines and Arduino board send correctly the 16bits in MOSI line but in MISO only LOW! so this is my code in Arduino IDE, I hope you can help me!
    
 
    #include <SPI.h>
uint8_t adcMSB = 0, adcLSB = 0;
unsigned int read_adc;
void setup()
{
  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV4); //master clock 4MHZ
  SPI.setDataMode(SPI_MODE3);               //mode SPI 3
  SPI.setBitOrder(MSBFIRST);
  pinMode(53,OUTPUT);     
  digitalWrite(53,HIGH);
  pinMode(46,OUTPUT);
  digitalWrite(46,HIGH);
  Serial.begin(9600);
}


void loop()
{
  digitalWrite(46,LOW);     //this start the conversion in specific pin CONVST
  delay(1);                              //wait the device busy pin
  digitalWrite(46,HIGH);     //and start the trans.
  digitalWrite(53,LOW);     //enable device
  adcMSB=SPI.transfer(0b11100001); //here I configure the bits in Control Register, read channel 1, power mode normal
  adcLSB=SPI.transfer(0b00010001); //this read from ADC OUTPUT DATA REGISTER, start the Conversion, select mode 2
  digitalWrite(53,HIGH); //disable device
  delay(300);
  
//read for results
  read_adc= word(adcMSB, adcLSB);
  Serial.print(read_adc,HEX);
  Serial.print(" ");
  Serial.println(read_adc,DEC);
  
}


    
 
    
 
    and this is my schematic:
    
									
			        
		
    

							
    
				
				
			
    
					
						
        

    
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													0
							
			
				
									
							        
			
			
			
        
            
						
                            
            
            				
            
                on Apr 17, 2013 7:21 PM
            
            
					
        
	
        

		
		
        
					
        I have a new version, in this version I read and write in ADC via SPI hardware:
        
 
        but i have problems with interfacing, I have waiting 15 ms and repeat the instruction as a minimum twice to read more than two channelss: this is the new version:
        
 

        
 
        #include <Expander32.h>
#include <SPI.h>

/*
Definitions to work all channels
*/
#define AN1 B11100001
#define AN2 B11110001
#define AN3 B11100101
#define AN4 B11110101
#define AN5 B11101001
#define AN6 B11111001
#define AN7 B11101101
#define AN8 B11111101

Expander32 expander(40, 41); //Enable pins to Expander32SS board

//uint8_t adcMSB1 = 0, adcLSB1 = 0;
//unsigned int read_adc1;

uint8_t RstADCMSB = B01000000;    //this command 
uint8_t RstADCLSB = B00000010;    //reset the spi in ADC
uint8_t CtrlRegMSB = B11100000;    //this command select the chhanel 1
uint8_t CtrlRegLSB = B00010001;    //this commans is the same to all channels
//uint8_t CtrlRegMSB = B11100001;
//uint8_t CtrlRegLSB = B00010001;

//uint8_t StatRegMSB = B11100001;
//uint8_t StatRegLSB = B10010001;

uint16_t AD1=0;
uint16_t AD2=0;
uint16_t AD3=0;
float Vin1=0, Vin2=0, Vin3=0;
float N=3.05194e-4;    //cte to voltaje convertion 5/((2^14)-1)
void setup()
{
  expander.init();        //initialitation of the Expander32SS board
  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV128);    //Spi to 125kHz
  SPI.setDataMode(SPI_MODE0);                //SPI in mode 0
  SPI.setBitOrder(MSBFIRST);          //send the most significant bit first
  pinMode(53,OUTPUT);
  digitalWrite(53,HIGH);        //Disable the ADC
  pinMode(12,OUTPUT);          
  digitalWrite(12,HIGH);        //PIN to convst ADC
  Serial.begin(9600);
  delay(150);              //Wait for ADC auto calibration
}

void loop()
{
  
  setChannel(AN1);            //What channel read?
  delayMicroseconds(10);    //wait the complete convertion 5us
  AD1 = readChannel();        //read the ADC value
  
//  delayMicroseconds(100);
//

  setChannel(AN2);            //What channel read?
  delayMicroseconds(10);    //wait the complete convertion
  AD2 = readChannel();        //read the ADC value
  
  Vin1=N*AD1;          //Voltaje convertion
  Vin2=N*AD2;          //Voltaje convertion
  
  /*Print the results in serial RS232*/
  Serial.print(Vin1, DEC);
  Serial.print("\t");
  Serial.print(AD1,DEC);
  Serial.print("\t");
  Serial.print(Vin2,DEC);
  Serial.print("\t");
  Serial.println(AD2,DEC); 
  
}

/*
Method to select the channel of ADC
*/
void setChannel(uint8_t channel){
  for (int i=1; i>=0; i--){    // this methos call twice and dont kwon why
  digitalWrite(12,LOW);        //start convertion 
  delayMicroseconds(1);        //
  digitalWrite(12,HIGH);       //
  delayMicroseconds(10);       //Wait a moment
  expander.Spin(16);        //Enable of SPin 16 in Expander32SS board 
  digitalWrite(53,LOW);      //Enable ADC
  SPI.transfer(channel);     //channel to set
  SPI.transfer(CtrlRegLSB);  //Same command all channels
  digitalWrite(53,HIGH);      //Disable ADC
  expander.disable();
  delay(15);                  //Wait 15 ms and dont kwon why
  }
}

/*
Method to read the value of ADC
*/
uint16_t readChannel(void){
  uint16_t out=0;
  uint8_t adcMSB=0;
  uint8_t adcLSB=0;
  for (int i=1; i>=0; i--){    // this methos call twice and dont kwon why
  digitalWrite(12,LOW);        //start convertion 
  delayMicroseconds(1);        //
  digitalWrite(12,HIGH);       //
  delayMicroseconds(10);       //Wait a moment
  expander.Spin(16);        //Enable of SPin 16 in Expander32SS board 
  digitalWrite(53,LOW);      //Enable ADC
  adcMSB=SPI.transfer(0x00);  //send 0x00 to generate clock signal 
  adcLSB=SPI.transfer(0x00);  //send 0x00 to generate clock signal
  digitalWrite(53,HIGH);      //Disable ADC
  expander.disable();
  delay(15);                  //Wait 15 ms and dont kwon why
  }
  out= word(adcMSB, adcLSB);

  return out;
}

        
 
        
 
        With this code the ADC don't stops but and I write to zero un bus spi to read the sample.
        
 

        
 
        best regards!
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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Reply

        


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													0
							
			
				
									
							        
			
			
			
          
            
						
                            
            
            				
            
                on Apr 17, 2013 7:21 PM
            
            
					
          
	
          

		
		
          
					
          I have a new version, in this version I read and write in ADC via SPI hardware:
          
 
          but i have problems with interfacing, I have waiting 15 ms and repeat the instruction as a minimum twice to read more than two channelss: this is the new version:
          
 

          
 
          #include <Expander32.h>
#include <SPI.h>

/*
Definitions to work all channels
*/
#define AN1 B11100001
#define AN2 B11110001
#define AN3 B11100101
#define AN4 B11110101
#define AN5 B11101001
#define AN6 B11111001
#define AN7 B11101101
#define AN8 B11111101

Expander32 expander(40, 41); //Enable pins to Expander32SS board

//uint8_t adcMSB1 = 0, adcLSB1 = 0;
//unsigned int read_adc1;

uint8_t RstADCMSB = B01000000;    //this command 
uint8_t RstADCLSB = B00000010;    //reset the spi in ADC
uint8_t CtrlRegMSB = B11100000;    //this command select the chhanel 1
uint8_t CtrlRegLSB = B00010001;    //this commans is the same to all channels
//uint8_t CtrlRegMSB = B11100001;
//uint8_t CtrlRegLSB = B00010001;

//uint8_t StatRegMSB = B11100001;
//uint8_t StatRegLSB = B10010001;

uint16_t AD1=0;
uint16_t AD2=0;
uint16_t AD3=0;
float Vin1=0, Vin2=0, Vin3=0;
float N=3.05194e-4;    //cte to voltaje convertion 5/((2^14)-1)
void setup()
{
  expander.init();        //initialitation of the Expander32SS board
  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV128);    //Spi to 125kHz
  SPI.setDataMode(SPI_MODE0);                //SPI in mode 0
  SPI.setBitOrder(MSBFIRST);          //send the most significant bit first
  pinMode(53,OUTPUT);
  digitalWrite(53,HIGH);        //Disable the ADC
  pinMode(12,OUTPUT);          
  digitalWrite(12,HIGH);        //PIN to convst ADC
  Serial.begin(9600);
  delay(150);              //Wait for ADC auto calibration
}

void loop()
{
  
  setChannel(AN1);            //What channel read?
  delayMicroseconds(10);    //wait the complete convertion 5us
  AD1 = readChannel();        //read the ADC value
  
//  delayMicroseconds(100);
//

  setChannel(AN2);            //What channel read?
  delayMicroseconds(10);    //wait the complete convertion
  AD2 = readChannel();        //read the ADC value
  
  Vin1=N*AD1;          //Voltaje convertion
  Vin2=N*AD2;          //Voltaje convertion
  
  /*Print the results in serial RS232*/
  Serial.print(Vin1, DEC);
  Serial.print("\t");
  Serial.print(AD1,DEC);
  Serial.print("\t");
  Serial.print(Vin2,DEC);
  Serial.print("\t");
  Serial.println(AD2,DEC); 
  
}

/*
Method to select the channel of ADC
*/
void setChannel(uint8_t channel){
  for (int i=1; i>=0; i--){    // this methos call twice and dont kwon why
  digitalWrite(12,LOW);        //start convertion 
  delayMicroseconds(1);        //
  digitalWrite(12,HIGH);       //
  delayMicroseconds(10);       //Wait a moment
  expander.Spin(16);        //Enable of SPin 16 in Expander32SS board 
  digitalWrite(53,LOW);      //Enable ADC
  SPI.transfer(channel);     //channel to set
  SPI.transfer(CtrlRegLSB);  //Same command all channels
  digitalWrite(53,HIGH);      //Disable ADC
  expander.disable();
  delay(15);                  //Wait 15 ms and dont kwon why
  }
}

/*
Method to read the value of ADC
*/
uint16_t readChannel(void){
  uint16_t out=0;
  uint8_t adcMSB=0;
  uint8_t adcLSB=0;
  for (int i=1; i>=0; i--){    // this methos call twice and dont kwon why
  digitalWrite(12,LOW);        //start convertion 
  delayMicroseconds(1);        //
  digitalWrite(12,HIGH);       //
  delayMicroseconds(10);       //Wait a moment
  expander.Spin(16);        //Enable of SPin 16 in Expander32SS board 
  digitalWrite(53,LOW);      //Enable ADC
  adcMSB=SPI.transfer(0x00);  //send 0x00 to generate clock signal 
  adcLSB=SPI.transfer(0x00);  //send 0x00 to generate clock signal
  digitalWrite(53,HIGH);      //Disable ADC
  expander.disable();
  delay(15);                  //Wait 15 ms and dont kwon why
  }
  out= word(adcMSB, adcLSB);

  return out;
}

          
 
          
 
          With this code the ADC don't stops but and I write to zero un bus spi to read the sample.
          
 

          
 
          best regards!
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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