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

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:

Parents
  • 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!

Reply
  • 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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