analog Encoder in Matlab and arduino

Hi

I have an encoder which it's channels are analog require, I mean these channels must be connected to the analog pins of the arduino board so, for reading this encoder I have a problem in Matlab, I know that there is a library for encoders in the Matlab and it should be written as:

a=arduino('com7','uno','Libraries','RotaryEncoder');
encoder=rotaryEncoder(a,'D2','D3',12)

but, as I said my encoder channels must be connected to the analog pins and I write this code:

a=arduino('com7','uno','Libraries','RotaryEncoder');
encoder=rotaryEncoder(a,'A0','A1',12)

and it could not be accepted and it shows an error that these pins are not correct for rotary encoder library

my question is how I could read my analog encoder pulses?

Answer 1

[Madhu Govindarajan]

Just go ahead and connect the encoder outs to digital pins that you have access to. Then use rotaryEncoder function on those digital pins while spinning the encoder by hand and use readCount to see if it shows results appropriately.

This should work just fine.

[john white]

tahnk you so much actually, I tested the rotaryEncoder function several days ago but it didn't work because the damage encoder was tested but, why in the Arduino program I must definite the encoder channels with analog pins but, in the Matlab I definite them with digital pins and it works in both of the softwares ?

[Madhu Govindarajan]

Here is a link to the encoder library that you are using in your Arduino sketch - https://www.pjrc.com/teensy/td_libs_Encoder.html

This plus the sensor link you provided shows that you are indeed using a quadrature encoder.

https://www.arduino.cc/reference/en/language/functions/digital-io/pinmode/

The Notes section on the link shows that 'A0' and 'A1' can be used as digital pins. This might be the reason why everything worked seemlessly on the Arduino sketch or maybe the encoder library uses pinMode function if it sees an analog pin and makes it a digital pin.

HTH,

Madhu

[john white]

ok thanks a lot

Answer 2

[Madhu Govindarajan]

The rotaryEncoder function is only going to work with quadrature encoders as noted in the documentation.

It seems to me like that analog encoders are usually potentiometers that have some sort of linear relationship between output voltage and degrees moved. You willl need to read the tech specification sheet or do your own testing to understand what the analog output voltages means with regards to the degree of the shaft. You can use the readVoltage function in MATLAB to bring in the voltages and establish the relationship.

Best bet for more help from community users - share existing arduino code to bring in data from this encoder or the spec sheet of the encoder itself.

[john white]

ok thank you for your answer

I write this code:

for i=1:1000
       
       pos = readVoltage(a,'A0');
       fprintf('Current knob position: %d\n',pos);
       pause(1);
   end

and it shows just 0 and 5 !

[Madhu Govindarajan]

Can you give more information on -

1) Is the encoder connected to a motor? If so, how fast is the motor spinning? If not, how are you controlling how fast the encoder is spinning.

2) What encoder are you using?

[john white]

actually for testing I just turn the magnet handly and the encoder is incremental magnetic

[Madhu Govindarajan]

When I google incremental magnetic encoders I get information about rotary encoders that are digital. Are you sure that yours is analog?

[john white]

yes ofcourse I test this encoder with Arduino program and when I connect the encoder pins to the analog pins of the Arduino board the code read the pulses correctly

[Madhu Govindarajan]

Please share the Arduino code you used to test it and possibly the wiring diagrams for the connections you made. Then it would be easier to tell if there are MATLAB equivalents or not.

[john white]

ok, there is the code:

#include <Encoder.h>
Encoder myEncoder(A0,A1);
double Position;
int t;
void setup() {
  Serial.begin(250000);
  Serial.println("DC POSITION.");
  
}
long oldPosition = -999;
void loop() {
  long newPosition = myEncoder.read();
  if (newPosition != oldPosition) {
    oldPosition = newPosition ;
  }
Serial.print("t");
Serial.println(t);
Serial.print("Position = ");
Serial.println(newPosition);

  analogWrite(5,60);
 
  digitalWrite(8,LOW);
  t=millis();
  if (t<2000){
     digitalWrite(7,HIGH);
  }     
  else if(t>=2000 && t<4000){ digitalWrite(7,LOW);
  digitalWrite(8,HIGH);
  }
  else{  digitalWrite(8,LOW);

  }
}
   

and there is the diagram:

[Madhu Govindarajan]

Could you also post a link to your encoder itself or provide its name? Because it seems more and more like this is a quadrature encoder, in which case you can use the rotaryEncoder function. The reason I ask for the link to encoder is if I can confirm that it is a quadrature encoder or an encoder that can be connected to digital pins then I can recommend exact steps.

Madhu

[john white]

I have the data sheet of the encoder, I attached it