Hi everyone!
So I have a ATMega project that is supposed to reflect a quadrature encoder, using a 10k potentiometer to increase/decrease the frequency and using a switch rocker to switch the signals so that it can represent if the quadrature is going forward or backwards. However, when I rotate the potentiometer and the frequency updates, it also switches the direction without me intending to. I was thinking I had an issue with my method that updates the frequency, but I wasn't too sure. I am using timer interrupts to toggle my signals.
volatile int signalA = 9; // Set signal A for pin 9
volatile int signalB = 12; // Set signal B for pin 12
const int potPin = A1; // Set potentiometer for pin A1
const byte switchPin = 38; // Set switch for pin 38
volatile byte switchState = 0; // Current state of switchPin
byte changeState = 0; // Variable to check to see if switchPin state value has changed
boolean toggleA = 0; // Toggle flag for signal A
boolean toggleB = 0; // Toggle flag for signal B
int value = 0; // Analog to digital value read in by potentiometer
int potval = 0; // Variable to check to see if potentiometer value has changed
int buf[4]; // Buffer for potentiometer values
int cumulative = 0; // Variable to hold all current buf values
int bufcount = 0; // Counter for buf
uint16_t intcount = 0; // Counter for LEDs
void setup() {
Serial.begin(9600);
pinMode(signalA, OUTPUT); // Initialize signal pins to be outputs
pinMode(signalB, OUTPUT);
pinMode(potPin, INPUT); // Set potentiometer pin to be input
pinMode(switchPin, INPUT_PULLUP); // The switch pin is an input pulled HIGH by an internal resistor
DDRA = B11111111; // Set PORTA to outputs
DDRC = B11111111; // Set PORTA to outputs
cli(); // Disable all interrupts
TCCR1A = 0; // Set timer
TCCR1B = 0;
TCNT1 = 0; // Set counter to 0. TCNT1 stores the timer 1 counter values
ICR1 = 199; // Set default ICR1 = [16Mhz / (desired frequency * prescaler)] - 1
OCR1A = ICR1 - 1; // Set Compare Match Register A to ICR1 at almost 100% duty cycle
OCR1B = OCR1A / 2; // set Compare Match Register B to OCR1A with 50% duty cycle
TCCR1B |= (1 << CS11); // Set prescaler
// CS10, CS11, CS12 are the clock select bits for Timer 1
// Each bit corresponds to a prescaler
// In this case, enabling CS11 will set the prescaler to 8.
TIMSK1 |= (1 << OCIE1A) | (1 << OCIE1B); // Enable Timer Compare Interrupt A & B
TCCR1B |= (1 << WGM13) | (1 << WGM12); // CTC mode with ICR1 = Clear timer when the counter reaches the compare match register
// This will set the two bits of WGM to 14
// Note: 1 << WGM12 is the same as TCCR1B = 32
sei(); // Enable all interrupts
}
void loop() {
switchState = PIND & 0b10000000; // Set switchState to only observe digital pin 38
if (changeState != switchState) { // If changeState does not equal the current state of the switchPin
switchPins(); // Call method to change the signal pins
changeState = switchState; // Set changeState to equal the current state of the switchPin
}
delay(100);
readPin(); // Read potentiometer pin
}
void switchPins() { // Change direction of quadrature
Serial.println("CHANGE");
int temp = signalB; // Create temp variable to hold pin value of signal B
signalB = signalA; // Switch signal B to equal signal A
signalA = temp; // Have signal A equal temp
}
void readPin() {
volatile int temp = analogRead(potPin); // Analog read from potPin and assigned to value
temp = temp >> 4; // Shift value by 4 bits to reduce range (1023/16) for smoother transition
if (bufcount < 4) { // If the bufcount is less than 4, have it equal the value of the potPin
buf[bufcount] = temp;
cumulative += buf[bufcount]; // Add and store buf into cumulative
bufcount++; // Increment bufcount
}
else { // If bufcount is now greater than the buf size
value = cumulative >> 2; // value is equal to cumulative/4
bufcount = 0; // Reset both bufcount and cumulative
cumulative = 0;
}
if (potval != value) { // If potval does not equal value, update the frequency
updatePin();
}
potval = value; // Set potval to equal value
}
void updatePin() {
if (value <= 49 && value >= 0) { // Set a limit for when potentiometer ADC value to 48 (49 is for 20kHz)
cli(); // Disable all interrupts
resetICR(99); // Set value
sei(); // Enable all interrupts
}
else if (value == 63) { // Stop all interrupts if potentiometer value is 63
cli(); // 63 is the "lowest" value the potentiometer can reach
}
else {
cli(); // Disable all interrupts
resetICR(value); // Otherwise, update frequency to acceptable value from the potentiometer
sei(); // Enable all interrupts
}
}
void resetICR(int input) {
intcount = 0;
TCCR1A = 0; // Set timers
TCCR1B = 0;
TCNT1 = 0; // Set counter to 0. TCNT1 stores the timer 1 counter values
ICR1 = input; // Set ICR1 = [16Mhz / (desired frequency * prescaler)] - 1
OCR1A = ICR1 - 1; // Set Compare Match Register A to ICR1 at almost 100% duty cycle
OCR1B = OCR1A / 2; // set Compare Match Register B to OCR1A with 50% duty cycle, toggling signal half a period later
TCCR1B |= (1 << CS11); // Set prescaler
// CS10, CS11, CS12 are the clock select bits for Timer 1
// Each bit corresponds to a prescaler
// In this case, enabling CS11 will set the prescaler to 8.
TIMSK1 |= (1 << OCIE1A) | (1 << OCIE1B); // Enable Timer Compare Interrupt A & B
TCCR1B |= (1 << WGM13) | (1 << WGM12); // CTC mode with ICR1 = Clear timer when the counter reaches the compare match register
}
ISR(TIMER1_COMPA_vect) { // Interrupt handler. Toggle signalA
if (toggleA) {
digitalWrite(signalA, HIGH);
// PORTA = intcount; // This code is for the binary counter for the 12 LEDs
// PORTC = intcount >> 4; // Additional port registers are shifted by 4 bits
// intcount++; // Increment counter
PORTA = 1 << intcount; // This code is for the sweeping LEDs
PORTC = 1 << intcount - 4; // Additional port registers are shifted by 4 bits
intcount++; // Increment counter
if (intcount == 12) { // Clear counter once it reaches 12 since there are 12 LEDs
intcount = 0;
}
toggleA = 0;
}
else {
digitalWrite(signalA, LOW);
toggleA = 1;
}
}
ISR(TIMER1_COMPB_vect) { // Interrupt handler. Toggle signalB
if (toggleB) {
digitalWrite(signalB, HIGH);
toggleB = 0;
}
else {
digitalWrite(signalB, LOW);
toggleB = 1;
}
}
