Recently found this code that takes an analog read value and converts it to a signal for a digi pot control, basically an analog pot controlling the digi pot. I'm using a MCP41050 which is confirmed working with other code.
#include <SPI.h>
// include the SPI library:
const int slaveSelectPin = 10; // set pin 10 as the slave select for the digital pot:
float valueAnalogPot; // potValue divided by 8. 1024 values/128 7 bit resistor resolution:
int digiPotData; // value of analog pot scaled and cast into an integer:
void setup() {
pinMode (slaveSelectPin, OUTPUT); // set the slaveSelectPin as an output:
SPI.begin(); // initialize SPI:
Serial.begin(9600); //serial communication to screen:
digitalPotWrite(0, 0);
delay(1);
digitalPotWrite(16, 0);
delay(1);
}
void loop() {
int potValue = analogRead(A0); //store ADC of pot value 0-1023 in potValue:
Serial.println(potValue); //print value between 0-1023 to screen int datatype:
//delay(1); //stability
valueAnalogPot = potValue / 8; // scaled to fit 7 bit pot:
digiPotData = (int) valueAnalogPot; //cast to integer to be used as data byte for digipot
int CommandByte = 0; // Pot 0 – Write Mode:
// change the resistance on this digital pot 0 to scaled version of the analog pot:
digitalPotWrite(CommandByte, digiPotData);
delay(10);
}
int digitalPotWrite(int CommandByte, int value) {
// take the SS pin low to select the chip:
digitalWrite(slaveSelectPin, LOW);
// send in the address and value via SPI:
SPI.transfer(CommandByte);
SPI.transfer(value);
// take the SS pin high to de-select the chip:
digitalWrite(slaveSelectPin, HIGH);
}
I can't get the digi pot wiper to move at all. It's stuck at about ~43k. This code was used for MCP4241. I've tried scaling the bit rate up to match the 41050 but no luck. What else could I be missing?
How exactly would I go about writing the correct sequence? Fairly new to SPI. When I try to change the power up values in void setup, I can't get it to even go through a check during a power up.
When I do this, it gives me an error saying that 'potvalue' is not declared... I made it an integer and the error went away but I dont know if thats normal or not.
Why not potValue = potValue >> 2;
Do you know that the 8 Bit AVRs have no DIV instruction and must do all divisions in code? Even if the compiler can optimize a division, the float conversion and later back again costs time and possibly also program memory.
Even with these changes, its still not doing anything. The way the address it's being fed is definitely the issue by looking at the data sheet. I have no idea how to change it. I was looking at this example to maybe gain an understanding:
#include <SPI.h>
byte address = 0x11;
int CS= 10;
int i=0;
void setup()
{
pinMode (CS, OUTPUT);
SPI.begin();
// adjust high and low resistance of potentiometer
// adjust Highest Resistance .
digitalPotWrite(0x00);
delay(1000);
// adjust wiper in the Mid point .
digitalPotWrite(0x80);
delay(1000);
// adjust Lowest Resistance .
digitalPotWrite(0xFF);
delay(1000);
}
void loop()
{
for (i = 0; i <= 255; i++)
{
digitalPotWrite(i);
delay(10);
}
delay(500);
for (i = 255; i >= 0; i--)
{
digitalPotWrite(i);
delay(10);
}
}
int digitalPotWrite(int value)
{
digitalWrite(CS, LOW);
SPI.transfer(address);
SPI.transfer(value);
digitalWrite(CS, HIGH);
}
Just a simple fade in fade out timed procedure. Maybe this is the one I should edit for external pot control? Thank y'all for the info so far.
Have you tried the code in post#13 again to prove your digipot is still working?
Do you have a DMM to measure the resistance?
It sounds a simple job to add the external control Pot.
Can you please post a circuit diagram of your porject, include the pot and digipot as well ass power connections?
A hand drawn schematic will be fine.
