[AVR] Arduino with digipot AD5293

[Rajiv Tyagi]

Digipot AD5293 is giving me a lot of trouble. Below is my code. I don't know why I can't get this to work or what I'm doing wrong. Can someone help, please?

[syntax=cpp]
#include <SPI.h>

void setup(){

  pinMode(10, OUTPUT); //CS
  pinMode(11, OUTPUT); //MOSI
  pinMode(12, INPUT);  //MISO
  pinMode(13, OUTPUT); //SCK

  Serial.begin(115200);

  writeCommand;
}

void loop(){
  unsigned int val;
  for (val = 0; val <= 1023; val++) {
    writeDigipots(val);
    //delay(10);
  }

  for (val = 1023; val > 0; val--) {
    writeDigipots(val);
    //delay(10);
  }

}


void writeDigipots(unsigned int val){
  SPI.beginTransaction(SPISettings(SPI_CLOCK_DIV8, MSBFIRST, SPI_MODE1));
  digitalWrite(10, LOW);
  //SPI.transfer(0x18); //send command byte
  //SPI.transfer(0x03);
  byte highbyte = val >> 8 + 0x04; //high wiper byte + command
  byte lowbyte = val & 0xFF;
  SPI.transfer(highbyte); //send wiper data high byte
  SPI.transfer(lowbyte); //send wiper data low byte
  digitalWrite(10, HIGH);
  SPI.endTransaction();
}

void writeCommand() {
  SPI.beginTransaction(SPISettings(SPI_CLOCK_DIV8, MSBFIRST, SPI_MODE1));
  digitalWrite(10, LOW);
  SPI.transfer(0x18); //send command high byte
  SPI.transfer(0x03); //send command low byte
  digitalWrite(10, HIGH);
  SPI.endTransaction();
}
[/syntax]

On the oscilloscope I can see the MOSI changing values, SCK is present and stable, CS is correct. What am I doing wrong?

Rajiv

 

[udayan92]

On the oscilloscope I can see the MOSI changing values, SCK is present and stable, CS is correct.

Does this happen in read mode/write mode?
Verify the timing and waveforms you saw in the oscilloscope with the timing diagram on page 8.https://www.analog.com/static/imported-files/data_sheets/AD5293.pdf

 

[Rajiv Tyagi]

0x1803 is the write control code. I am only writing to the digipot...

 

[udayan92]

Looks like you did not include the header file for the microcontroller which is running the SPI protocol.Include the microcontroller header file also.Then,the system might work.
Also,are the functions digitalWrite,SPI.transfer,SPI.beginTransaction a part of <SPI.h>?
If not,then they will not work,if you haven't defined them anywhere in the program.

 

[Rajiv Tyagi]

Yes, those are all SPI methods from the SPI Library built into the Arduino IDE. I am getting no compiler errors - everything compiles without any warning or error messages.

Could you please check if I am sending the data correctly? Starting with the 0x1803 control code and the masking of the two bytes I send in the writeDigipots() function? The Analog Devices datasheet is so sketchy, I wonder how people get their digipots working? Their help is almost non-existent - the designated helper on the AD line knows almost nothing about the device and just advises to compare waveforms with the datasheet...