Why do I use this module? There is a feedback resistor in Op-Amp negative amplifier and it is not handy when you use hand to adjust the feedback resistor so I decide to use digital potentionmeter as an auto-again adjustment (AAA)
Step 0: hardware connection
pin 2, 3, 4 —> INC, U/D, CS
pin A0 –> RW
2 resistors 100Ω: pull-up at RH and pull-down at RL
Step 1: go to https://sites.google.com/site/tfagerscode/home/digipotx9cxxx download the library and paste it in your Arduino library.
Step 2:
/*
* Date: Wed, 03/05/2017
* Desc: Test digital potentionmeter X9C104
* the initial pot_index will be zero
*/
#include <DigiPotX9Cxxx.h>
#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>
DigiPot pot(2,3,4);
#define I2C_ADDR 0x3F
#define BACKLIGHT_PIN 3
#define En_pin 2
#define Rw_pin 1
#define Rs_pin 0
#define D4_pin 4
#define D5_pin 5
#define D6_pin 6
#define D7_pin 7
LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);
char incomingChar;
int pot_index;
const int analogInPin = A0;
int sensorValue = 0;
void setup() {
// Return value of pot to zero
for (int i=0; i<100; i++){
pot.decrease(1);
delay(10);
}
pot_index = 0;
// Initial device
Serial.begin(9600);
Serial.println("Starting ...");
lcd.begin(16,2);
lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE);
lcd.setBacklight(HIGH);
sensorValue = analogRead(analogInPin);
display_lcd(pot_index, sensorValue);
delay(1000);
}
void loop() {
// receive '1' to increase, '0' to decrease
if (Serial.available()){
incomingChar = (char) Serial.read();
if (incomingChar == '1'){
if(pot_index >= 100){
Serial.println("Pot index reaches maximum limit.");
lcd.clear();
lcd.print("Maximum limit");
}else{
pot.increase(1);
pot_index ++;
sensorValue = analogRead(analogInPin);
display_lcd(pot_index, sensorValue);
}
}
else if (incomingChar == '0'){
if (pot_index <= 0){
Serial.println("Pot index reaches minimum limit.");
lcd.clear();
lcd.print("Minimum limit");
}else{
pot.decrease(1);
pot_index --;
sensorValue = analogRead(analogInPin);
display_lcd(pot_index, sensorValue);
}
}else{
Serial.println("Something wrong happens.");
lcd.clear();
lcd.print("Error");
}
}
}
void display_lcd(int p_index, int p_value){
lcd.clear();
lcd.print("pot index: ");
lcd.setCursor(11,0);
lcd.print(p_index);
lcd.setCursor(0,1);
lcd.print("pot value: ");
lcd.setCursor(11,1);
lcd.print(p_value);
}
There are two definition of pot, pot_index and pot_value. Pot_index will be from 0 to 100. That is the value of X9C104 we control. Pot_value is the analog feedback on pin A, it will be from 0 to 1023. However I added 2 resistor: pull-up resistor at pin RH and pull-down resistor at pin RL so the value of analog A0 will be from 8 to 1008 (or from 4 to 1004 ... ADC still has some tolerance, let's say)
Why needs amplifying? Something the signal is too small to determine is the reading value a noise or a real value? You will see the usefulness of digital potentionmeter in my project Dimmer with current feedback.
