Using two encoders on one Arduino Mega 2560, second channel will only count up

Projects Programming
1

I am trying to use two encoders on one Arduino Mega 2560, on encoder for each wheel.

The first channel using Pin A=2 and Pin B=4, works great no issues.
The second channel using Pin A=3 and Pin B=4, the interrupt comes thru but it will only count in one direction).

If I put the encode for the second channel on the first channel, it works fine.

Any ideas?

Here is the code:
// Rotary Encoder Inputs

//Pin 2 and 3 can have external interrupts on them
//Pin 18 and 19 can also have external interrupts

int Encoder1_PinA = 2;
int Encoder1_PinB = 4;

int Encoder1_counter_2 = 0;
volatile int Encoder1_counter = 0;

int Encoder2_PinA = 3;
int Encoder2_PinB = 5;

int Encoder2_counter_2 = 0;
volatile int Encoder2_counter = 0;

volatile int Encode1_PinB_Value =0;
volatile int Encode2_PinB_Value =0;

char in_char;
unsigned long my_time;

String send, send2, info, info2, tab = "\t";

unsigned long start, stop, elapsed;
int Encoder1_pin_a = Encoder1_PinA, Encoder1_pin_b = Encoder1_PinB;
int Encoder2_pin_a = Encoder2_PinA, Encoder2_pin_b = Encoder2_PinB;

void setup()
{
pinMode(Encoder1_PinA, INPUT);
pinMode(Encoder1_PinB, INPUT);
pinMode(Encoder2_PinA, INPUT);
pinMode(Encoder2_PinB, INPUT);//INPUT_PULLUP

//PCMSK2 |= (1 << PCINT18) | (1 << PCINT19);

Serial.begin(115200);

start = millis();

attachInterrupt(digitalPinToInterrupt(Encoder1_pin_a), Encoder1_change, RISING);
attachInterrupt(digitalPinToInterrupt(Encoder2_pin_a), Encoder2_change, RISING);

Serial.println("Ready to go");
}

void Encoder1_change()
{
Encode1_PinB_Value =digitalRead(Encoder1_pin_b);

if (Encode1_PinB_Value == HIGH)
{
Encoder1_counter = Encoder1_counter - 1;
}
else
{
Encoder1_counter = Encoder1_counter + 1;
}
}

void Encoder2_change()
{
Encode2_PinB_Value =digitalRead(Encoder2_pin_b);
if (Encode2_PinB_Value == HIGH)
{
Encoder2_counter = Encoder2_counter - 1;
}
else
{
Encoder2_counter = Encoder2_counter + 1;
}
}

void DisplayPins()
{
Serial.print(" Encoder1[");
if (digitalRead(Encoder1_pin_a) == HIGH)
{
Serial.print("PinA=High ");
}
else
{
Serial.print("PinA=Low ");
}

if (digitalRead(Encoder1_pin_b) == HIGH)
{
Serial.print(" PinB=High ");
}
else
{
Serial.print(" PinB=Low ");
}
Serial.print(" PinB_Value="); Serial.print(Encode1_PinB_Value, DEC);
Serial.print("] ");

Serial.print(" Encoder2[");
if (digitalRead(Encoder2_pin_a) == HIGH)
{
Serial.print("PinA=High ");
}
else
{
Serial.print("PinA=Low ");
}

if (digitalRead(Encoder2_pin_b) == HIGH)
{
Serial.print("PinB=High ");
}
else
{
Serial.print("PinB=Low ");
}
Serial.print(" PinB_Value="); Serial.print(Encode2_PinB_Value, DEC);
Serial.println("]");
}

void loop()
{
if (Encoder1_counter != Encoder1_counter_2)
{
noInterrupts();
info = (String)Encoder1_counter;
Encoder1_counter_2 = Encoder1_counter;
interrupts();
send = info;
Serial.print("1-->");
Serial.print(send);
DisplayPins();
}

if (Encoder2_counter != Encoder2_counter_2)
{
noInterrupts();
info = (String)Encoder1_counter;
Encoder1_counter_2 = Encoder1_counter;

info2 = (String)Encoder2_counter;
Encoder2_counter_2 = Encoder2_counter;
interrupts();

send = info;
send2 =info2;
Serial.print("2-->");
Serial.print(" [1]-->");
Serial.print(send);
Serial.print(" [2]-->");
Serial.print(send2);
DisplayPins();
}

while (Serial.available() > 0)
{
char ch = Serial.read();
Serial.print(ch);
if(ch =='r')
{
Serial.println("Reset encoder");

noInterrupts();
Encoder1_counter=0;
Encoder1_counter_2= 0;
interrupts();
}
if(ch == 'i')
{
DisplayPins();
}
}
}

2

you might find reading this other thread helpful, https://forum.arduino.cc/index.php?topic=681420.0, He's working on code to service 43 encoders.

if you have a single routine that works for one encoder, it should work for another encoder

3

Please edit your post to add code tags, as described in "How to use this forum".

4

Not sure I can see why the two encoders are different (why not using INPUT_PULLUP everywhere?)

But I notice a lack of critical section covering some variable accesses:

 if (Encoder1_counter != Encoder1_counter_2)  <<< Encoder1_counter read not in critical section
  {
    noInterrupts();
    info = (String)Encoder1_counter;  <<< read in critical section, but greatly slowed by allocating a String
    Encoder1_counter_2 = Encoder1_counter;
    interrupts();
    send = info;
    Serial.print("1-->");
    Serial.print(send);
    DisplayPins();
  }

You should be putting all variable access in one critical section and do nothing else but copy them to locals:

  noInterrupts() ;
  int counter_copy = Encoder1_counter ;  // read variable once in critical section, as quick as possible
  interrupts() ;
  if (counter_copy != Encoder1_counter_2)
  {
    Encoder1_countre_2 = counter_copy ;
    info = (String) counter_copy;
    send = info;
    Serial.print("1-->");
    Serial.print(send);
    DisplayPins();
  }