X9241A - Digital Potentiometer

Revision as of 02:33, 14 September 2008

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Summary

Example of Method

I2C

There are basically only two functions that I am after right now which are both three byte instructions:

• Read WCR(Wiper Control Register) for the four potentiometers 0-3 (So far this is failing miserably)
  • Send 1st byte - Address (my circuit - 01011010 or 0x2D)(binary - 0101 A3 A2 A1 A0) A values are actual pins set to high or low for an address.
  • Send 2nd byte - Instruction (binary - 1001 (1/0)(1/0) 00) - The two bits are used to choose the potentiometer
  • Read WCR requested Byte
• Write WCR for the four potentiometers 0-3 (This works)
  • Send 1st byte - Address (my circuit - 01011010 or 0x2D)(binary - 0101 A3 A2 A1 A0) A values are actual pins set to high or low for an address.
  • Send 2nd byte - Instruction (binary - 1010 (1/0)(1/0) 00) - The two bits are used to choose the potentiometer
  • Send WCR Byte - Potentiometer value (binary - 00 D5 D4 D3 D2 D1 D0) - D values are the 0-63 potentiometer positions

Sample Code

       Wire.beginTransmission(X9241_I2C_ADDRESS);
       Wire.send(0xa0); //Instruction to write WCR-00
       Wire.send(0x20); //Send a D value of 32
       Wire.endTransmission();

x9241A_Digital_Potentiometer_v.01 code

/*
 * x9241A Digital Potentiometer v.01
 * by <http://www.combustory.com> John Vaughters
 *
 * This Program illustrates the use of I2C to set up the x9241A Digital Potentiometer by setting and transferring the registers.
 * I attempted to read the register data through I2C, but was unable to get it to work.
 * Since the reading part was not so important to me I stopped trying.  
 * To set the registers up and transfer them to the Wiper registers met my goals and that is where I stopped.
 *
 * The x9142A has four Digital Pots and each pot has four static registers and one dynamic register the Wiper Control Register (WCR). 
 * Therefore, there are 16 total bytes of storage and four WCR's.
 * This Program has the following commands:
 * S - Set the 16 registers.  Each pot has four registers and this command will set each register group with the same value. So register 00 for each pot will
 *     be the same value for each pot, and the same for register 01 through 11.
 * G(0-3) - Global Transfer of Registers to the WCR's.  This command will bulk load the values stored in registers into the WCR's.  
 *          For example, a G0 will load the 00 register for each pot into the WCR in one command. A G1 loads the 01 register for each pot, etc.
 * (0-3)(0-3) - This set of commands transfers a single register into a single WCR. The digits are arranged like this (WCR)(Reg). 
 *              For example, a 00 command will load register 00 into WCR 00 or a 13 command will load register 11 into WCR 01, etc.
 * W(0-3) - This command writes directly to the WCR.  I have created four values that are just random, but the command shows how to write directly to the WCR for each pot.
 *          For example, a W0 command will write a value of decimal 16.  These commands are just for example purposes.
 *
 * Command Note: If you enter a command that is not recognized, then it is ignored and nothing happens and nothing is printed.
 */
 

#include "Wire.h"
#define X9241_I2C_ADDRESS 0x2D

// Global Variables
long command;
  

void setup() {
  Wire.begin();
  Serial.begin(57600);
  
}

void loop() {
   if (Serial.available()) {      // Look for char in serial que and process if found
      command = Serial.read();
      if (command == 83) {      //If command = "S" Set Register Data
      // This sets the four registers of each Digital Pot
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc0);  // This is the set register command c and the 16 registers are 0-f
          Wire.send(0x0a);  // This line is the value to set the register: 0-63 is a valid setting
          Wire.endTransmission(); 
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc1);
          Wire.send(0x14);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc2);
          Wire.send(0x20);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc3);
          Wire.send(0x3c);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc4);
          Wire.send(0x0a);
          Wire.endTransmission(); 
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc5);
          Wire.send(0x14);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc6);
          Wire.send(0x20);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc7);
          Wire.send(0x3c);
          Wire.endTransmission();
          delay(100);          
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc8);
          Wire.send(0x0a);
          Wire.endTransmission(); 
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xc9);
          Wire.send(0x14);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xca);
          Wire.send(0x20);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xcb);
          Wire.send(0x3c);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xcc);
          Wire.send(0x0a);
          Wire.endTransmission(); 
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xcd);
          Wire.send(0x14);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xce);
          Wire.send(0x20);
          Wire.endTransmission();
          delay(100);
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xcf);
          Wire.send(0x3c);
          Serial.println("cmd: S");
       }   
       else if (command == 71) {      //If command = "G" Transfer Global Register Data   
        delay(100);
        if (Serial.available()) {
         command = Serial.read(); 
         if (command == 48) {        // If command = "0" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0x10); // Global Load WCR's with Reg-00
          Wire.endTransmission();
          Serial.println("cmd: G0");
         }
         else if (command == 49) {        // If command = "1" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0x11); // Global Load WCR's with Reg-01
          Wire.endTransmission();
          Serial.println("cmd: G1");
         }
         else if (command == 50) {        // If command = "2" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0x12); // Global Load WCR's with Reg-10
          Wire.endTransmission();
          Serial.println("cmd: G2");
         }
         else if (command == 51) {        // If command = "3" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0x13); // Global Load WCR's with Reg-11
          Wire.endTransmission();
          Serial.println("cmd: G3");
         }
        }
       }
       
       else if (command == 48) {      //If command = "0" Transfer Register-00 Data to WCR 0-3
         delay(100);
         if (Serial.available()) {
         command = Serial.read(); 
         if (command == 48) {              // If command = "0" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xd0); // Load WCR-00 with Reg-00
          Wire.endTransmission();
          Serial.println("cmd: 00");
         }
         else if (command == 49) {        // If command = "1" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xd1); // Load WCR-00 with Reg-01
          Wire.endTransmission();
          Serial.println("cmd: 01");
         }
         else if (command == 50) {        // If command = "2" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xd2); // Load WCR-00 with Reg-10
          Wire.endTransmission();
          Serial.println("cmd: 02");
         }
         else if (command == 51) {        // If command = "3" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xd3); // Load WCR-00 with Reg-11
          Wire.endTransmission();
          Serial.println("cmd: 03");
         }
        }
       }
        else if (command == 49) {      //If command = "1" Transfer Register-01 Data to WCR 0-3
         delay(100);
         if (Serial.available()) {
         command = Serial.read(); 
          if (command == 48) {              // If command = "0" 
           Wire.beginTransmission(X9241_I2C_ADDRESS);
           Wire.send(0xd4); // Load WCR-01 with Reg-00
           Wire.endTransmission();
           Serial.println("cmd: 10");
          }
          else if (command == 49) {        // If command = "1" 
           Wire.beginTransmission(X9241_I2C_ADDRESS);
           Wire.send(0xd5); // Load WCR-01 with Reg-01
           Wire.endTransmission();
           Serial.println("cmd: 11");
          }
          else if (command == 50) {        // If command = "2" 
           Wire.beginTransmission(X9241_I2C_ADDRESS);
           Wire.send(0xd6); // Load WCR-01 with Reg-10
           Wire.endTransmission();
           Serial.println("cmd: 12");
          }
          else if (command == 51) {        // If command = "3" 
           Wire.beginTransmission(X9241_I2C_ADDRESS);
           Wire.send(0xd7); // Load WCR-01 with Reg-11
           Wire.endTransmission();
           Serial.println("cmd: 13");
          }
         }
        }
        else if (command == 50) {      //If command = "2" Transfer Register-10 Data to WCR 0-3
         if (Serial.available()) {
          command = Serial.read(); 
          if (command == 48) {              // If command = "0" 
           Wire.beginTransmission(X9241_I2C_ADDRESS);
           Wire.send(0xd8); // Load WCR-10 with Reg-00
           Wire.endTransmission();
           Serial.println("cmd: 20");
          }
         else if (command == 49) {        // If command = "1" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xd9); // Load WCR-10 with Reg-01
          Wire.endTransmission();
          Serial.println("cmd: 21");
         }
         else if (command == 50) {        // If command = "2" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xda); // Load WCR-10 with Reg-10
          Wire.endTransmission();
          Serial.println("cmd: 22");
         }
         else if (command == 51) {        // If command = "3" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xdb); // Load WCR-10 with Reg-11
          Wire.endTransmission();
          Serial.println("cmd: 23");
         }
        }
       }
       else if (command == 51) {      //If command = "3" Transfer Register-11 Data to WCR 0-3
        delay(100);
        if (Serial.available()) {
         command = Serial.read(); 
        if (command == 48) {              // If command = "0" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xdc); // Load WCR-11 with Reg-00
          Wire.endTransmission();
          Serial.println("cmd: 30");
         }
         else if (command == 49) {        // If command = "1" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xdd); // Load WCR-11 with Reg-01
          Wire.endTransmission();
          Serial.println("cmd: 31");
         }
         else if (command == 50) {        // If command = "2" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xde); // Load WCR-11 with Reg-10
          Wire.endTransmission();
          Serial.println("cmd: 32");
         }
         else if (command == 51) {        // If command = "3" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xdf); // Load WCR-11 with Reg-11
          Wire.endTransmission();
          Serial.println("cmd: 33");
         }
        }
       }
       else if (command == 87) {      //If command = "W" write directly to WCR 0-3
        delay(100);
        if (Serial.available()) {
         command = Serial.read(); 
        if (command == 48) {              // If command = "0" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xa0); //Instruction to write WCR-00
          Wire.send(0x10); //Send a D value of 16
          Wire.endTransmission();
          Serial.println("cmd: W0");
         }
         else if (command == 49) {        // If command = "1" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xa4); //Instruction to write WCR-01
          Wire.send(0x20); //Send a D value of 32
          Wire.endTransmission();
          Serial.println("cmd: W1");
         }
         else if (command == 50) {        // If command = "2" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xa8); //Instruction to write WCR-10
          Wire.send(0x2a); //Send a D value of 26
          Wire.endTransmission();
          Serial.println("cmd: W2");
         }
         else if (command == 51) {        // If command = "3" 
          Wire.beginTransmission(X9241_I2C_ADDRESS);
          Wire.send(0xac); //Instruction to write WCR-11
          Wire.send(0x30); //Send a D value of 48
          Wire.endTransmission();
          Serial.println("cmd: W3");
         }
        }
       }
    }
}
//*****************************************************The End***********************

x9241A_Digital_Potentiometer_v.01 User Guide

Commands

Troubleshooting

Summary

Quick Test