Simple encoder code not working

[olympique71]

Hi everyone,

So here's my problem. I'm actually using an Arduino nano to read an encoder (link) that has 1024 PPR. It is way too precise for what I want to do (simply get the rpm of a shaft) 0~300 RPM max. For this purpose, I decided to simply use one channel and simply count it on a rising front.

I made my lecture, so I attached channel A to an interrupt pin and the channel B too because I read on another thread that sometime, the second channel needs to be on a pull-up pin or something like that.

Also, I already succeeded to make it work with the library "Encoder.h", but it doesn't fit my needs as I need to read other sensors too and communicate via i2c and interrupts simply cut the communication. And when I used that library, from the moment you write the line myEncoder.read(), the interrupt pins will always work. I tried to use noInterrupts();, but everything stopped working.

That's why I decided to create my own code as it is relatively simple. However, using this code, I was hoping everything would work, but nothing appears in the Serial monitor. I even tried to write Serial.println("test"); inside the void loop(){} but it didn't print anything at all.

Also, another problem is that when the magnet isn't near the encoder it doesn't print anything (when I use it with the Encoder.h library) it should print 0 but instead it prints nothing.

#define PINA 2
#define PINB 3
volatile uint32_t rotaryCount = 0;

void count()
{
  rotaryCount++;
}

void setup ()
{
  pinMode(PINA, INPUT_PULLUP);
  pinMode(PINB, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(PINA), count, RISING);  
  Serial.begin (115200);
} 

void loop ()
{
    Serial.println(rotaryCount);
    delay(100);
} 

[jremington]

@olympique71

I attached channel A to an interrupt pin and the channel B too

Not a good idea. Remove the B connection. Please post a wiring diagram (hand drawn preferred), showing all the connections to the encoder, with pins clearly labeled.

With TTL outputs, you usually need a pullup resistor. It may be sufficient to use pinMode(pin, INPUT_PULLUP);, but if not, use 4.7K to 5V.

I recommend using the Arduino encoder library.

To read RPM, use an encoder with MUCH reduced resolution. Interrupts will saturate the Arduino with a 1024 PPR encoder, leaving no time for anything else.

[cattledog]

The linked encoder has a z output of one pulse per revolution.

Channels A, B, Z

You can read that with an interrupt.

[olympique71]

First of all, here's the wiring diagram.

@jremington

I recommend using the Arduino encoder library.

What is the pros of using it ? because I have 3 other sensors that I need to read too. If I'm using the library, I can't just shut off the interrupt pins when reading other sensors, compared to my actual code.

@jremington

use an encoder with MUCH reduced resolution

As @cattledog said, if I use the Z channel it is almost nothing for the arduino right?

I'll try it soon and keep you posted guys!

[cattledog]

@olympique71

if I use the Z channel it is almost nothing for the arduino right?

Correct. At 300 rpm that's 5 per second or 200 ms between interrupts. For a 16MHz processor that's a snooze.

[olympique71]

Ok so using this code, nothing prints. Very weird, even the string "test" doesn't print in the serial monitor and I have the matching baud rate..

Even if there's nothing happening on pin 2, I should still see "test" in the monitor ?!

#define PINA 2
volatile uint32_t rotaryCount = 0;

void count(){
  rotaryCount++;
}

void setup(){
  pinMode(PINA, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(PINA), count, RISING);  
  Serial.begin (115200);
} 

void loop(){
    Serial.println(rotaryCount);
    delay(1000);
    Serial.print("test"); // Simply to see if it can print something
} 

[GolamMostafa]

Please, post a link to the data sheets of your product: ERCK 05TTL 1024. The link you have mentioned in post #1 takes to a brief product/sales specification page.

[olympique71]

I just edited the link.

[JCA34F]

Try this test, turn encoder very slowly, see if the LED "L" blinks.

#define pinA 2
#define pinB 3
volatile uint32_t rotaryCount = 0;
uint32_t rotaryCountCopy;
void count()
{
  rotaryCount++;
  bitWrite(PORTB,5, !bitRead(PINB,5)); // toggle LED L
}

void setup ()
{
  pinMode(pinA, INPUT_PULLUP);
  pinMode(pinB, INPUT_PULLUP);
  pinMode(LED_BUILTIN,OUTPUT);
  attachInterrupt(digitalPinToInterrupt(pinA), count, RISING);  
  Serial.begin (115200);
} 

void loop ()
{
    noInterrupts();
    rotaryCountCopy = rotaryCount;
    interrupts();
    Serial.println(rotaryCountCopy);
    delay(100);
}

[GolamMostafa]

@olympique71

I need to read other sensors too and communicate via i2c

Thanks for the link of data sheets of the encoder.

Please, mention the sensor which you are operating uisng I2C Bus along with your encoder.

First check : Slowly turn the shaft of your encoder by one rotation and chcek that you can acquire/display ~4096 pulses for both Ch-A and Ch-B. Use both polling and interrupt methods.

Do you need to know the direction of rotation/movement?

[cattledog]

@olympique71

if there's nothing happening on pin 2, I should still see "test" in the monitor ?!

Correct.

Do you see output if you put some serial printing in setup()?

If you don't attach the interrupt do you see the serial output in loop()??

[JCA34F]

@olympique71

#define PINA 2

Do you get a "redefined" error warning when you compile? I did.

[olympique71]

@GolamMostafa

Do you need to know the direction of rotation/movement?

No.

@cattledog

Do you see output if you put some serial printing in setup()?

Problem solved, I had many IDE pages opened, I closed them all and reopen only my active project and it seems to have worked

@JCA34F

Do you get a "redefined" error warning when you compile?

Negative.

@JCA34F thanks to you, it's a nice feature to blink the LED "L" didn't know !

Here is my updated code working

#include "Wire.h"
#define pinZ 2
#define SHT20_ADDRESS 0x40 // Define the I2C address of the SHT20 sensor

volatile uint32_t rotaryCount = 0;

// variables for encoder
const unsigned long timePeriod = 5000;
unsigned long startTime;
long startPosition;
long oldPosition = -999;

 void count(){
   rotaryCount++;
   bitWrite(PORTB,5, !bitRead(PINB,5)); // toggle LED L
 }

void setup() {
  pinMode(LED_BUILTIN,OUTPUT);
  pinMode(pinA, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(pinA), count, RISING);  
  Serial.begin(115200);
  Wire.begin();
}

void loop() {
  getTemp();
  readEncoder();
  delay(500);
}

void readEncoder(){
  unsigned long now = millis();
  rotaryCount = 0;
  startPosition = rotaryCount;
  while(millis() - now < timePeriod){}
  long newPosition = rotaryCount;

  float speed = (newPosition - startPosition) / (float)timePeriod * 1000 * 60;
  Serial.print("Avg speed is ");
  Serial.println(speed, 2);
  rotaryCount = 0;
}

 void getTemp(){
  Wire.beginTransmission(SHT20_ADDRESS); // Tell the sensor we want to read data
  Wire.write(0xF5); // Send the command to measure humidity
  Wire.endTransmission();

  delay(100); // Wait for the measurement to complete

  Wire.requestFrom(SHT20_ADDRESS, 3); // Request 3 bytes of data from the sensor
  while (Wire.available() < 3); // Wait for all the bytes to arrive

  uint16_t rawHumidity = Wire.read() << 8 | Wire.read(); // Combine the two bytes of data into a single 16-bit value
  Wire.read(); // Discard the checksum byte

  float humidity = -6 + 125 * (float)rawHumidity / 65536; // Convert the raw data to percent relative humidity

  Wire.beginTransmission(SHT20_ADDRESS); // Tell the sensor we want to read data
  Wire.write(0xF3); // Send the command to measure temperature
  Wire.endTransmission();

  delay(100); // Wait for the measurement to complete

  Wire.requestFrom(SHT20_ADDRESS, 3); // Request 3 bytes of data from the sensor
  while (Wire.available() < 3); // Wait for all the bytes to arrive

  uint16_t rawTemp = Wire.read() << 8 | Wire.read(); // Combine the two bytes of data into a single 16-bit value
  Wire.read(); // Discard the checksum byte

  float temperature = -46.85 + 175.72 * (float)rawTemp / 65536; // Convert the raw data to Celsius

  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" C");
  Serial.print("Humidity: ");
  Serial.print(humidity);
  Serial.println(" %RH");
}

[GolamMostafa]

@olympique71

 Wire.requestFrom(SHT20_ADDRESS, 3); // Request 3 bytes of data from the sensor
  while (Wire.available() < 3); // Wait for all the bytes to arrive

The control will not be transferred to the next line of requestFrom() method until 3-byte data are received and stored in the I2C Serial Buffer; so, why to execute this code: while(Wire.available()<3);?

@olympique71

while(millis() - now < timePeriod){}

You are blocking the MCU for 5-sec -- is it good?

@olympique71

long newPosition = rotaryCount;

You are reading a 4-byte wide variable whose value might change even before the read is complete. This is a critical section which you are not protecting/guarding. Your speed measurement could be erroneous.

[olympique71]

@GolamMostafa

so, why to execute this code: while(Wire.available()<3);?

Honestly, this part I don't really know, took it from an example sketch and I thought it is to be more robust ?!

@GolamMostafa

You are blocking the MCU for 5-sec -- is it good?

Yeah, I'm not sure if it's the best way to proceed, but I wait for 5 seconds and count the number of pulses that I got in 5 seconds and then I can get the average speed from a 5 seconds measure.

@GolamMostafa

You are reading a 4-byte wide variable whose value might change even before the read is complete.

I'm really sure to get what you are trying to say. This part of code below is used to reset the count and then wait 5 seconds to get the number of pulses and then compute the speed from the pulses.

  unsigned long now = millis();
  rotaryCount = 0;
  startPosition = rotaryCount;
  while(millis() - now < timePeriod){}
  long newPosition = rotaryCount;

[camsysca]

What, no one challenged this?

Surely, the encoder needs stable 5V and GND. Grounding the Z output isn't good, either.

Anyway, good luck.

[olympique71]

oups, you're right, channel Z is unpluged and the ground of the encoder is connected to the arduino ground.