Comments on: Vigorius stirring redefined. Part 2 – electronics

By: Reading rotary encoder on Arduino « Circuits@Home

Reading rotary encoder on Arduino « Circuits@Home — Mon, 12 Apr 2010 21:44:29 +0000

[...] cheap low-quality encoders, but is somewhat cryptic and difficult to understand. Soon after posting one of my projects where I used rotary encoder to set motor speed i started receiving e-mails asking to explain the [...]

By: Cory

Cory — Sat, 13 Mar 2010 20:23:14 +0000

Duh! I should have known that lol

Thanks again,
Cory

By: oleg

oleg — Thu, 11 Mar 2010 05:14:55 +0000

If you want your enc_value to be larger than 255, it needs to be declared as unsigned int. It’s currently declared as byte AKA unsigned char which is 8 bits.

By: Cory

Cory — Thu, 11 Mar 2010 05:00:12 +0000

I really like the simplicity of this code and I want to use it in my project, but I’m running into a problem. My encoders are 624 counts per revolution but the code seems to max out at 255 even if I change the :
if( enc_value == 255 ) to if( enc_value == 624 ) .

I even tried changing from PINC to PINB thinking that the analog pins were maxed at 255.

Thanks,
Cory

By: oleg

oleg — Thu, 31 Dec 2009 19:05:22 +0000

Somehow your previous post with code ended up in spam folder and I haven’t noticed it until today. Anyway, It’s nice that you had encoder control sorted out!

By: Brad

Brad — Thu, 31 Dec 2009 03:37:27 +0000

After a bit of twiddling I got it working – Oleg, I have to say that this is THE most elegant rotary encoder solution I have seen. I have spent the past week or so working with different routines for quadrature encoders and this is just absolutely awesome.

Thanks very much!

Brad

By: Brad

Brad — Thu, 31 Dec 2009 03:21:28 +0000

Oleg, yours is the most elegant and simple code for reading an encoder I have seen… only it doesn’t work for me! Would you mind looking over what I have here and possibly giving me a suggestion?

#include #fuses HS,NOWDT,NOPROTECT,NOLVP,BROWNOUT,PUT,NOPBADEN,DEBUG #use delay(clock=20M) #use rs232(baud=115200,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8) #include


signed char enc_states[] = {0,-1,1,0,1,0,0,-1,-1,0,0,1,0,1,-1,0};

byte old_AB = 0;

byte enc_value = 127;

byte old_enc_value = 0;
void encoder0Loop(void) {     // int8 enc_value

   old_AB <<= 2;    //remember previous state by shifting the lower bits up 2

   old_AB |= ( portb & 0x03 );      // AND the lower 2 bits of port b, then OR them with var old_AB to set new value

   enc_value += enc_states[( old_AB & 0x0f )];     // the lower 4 bits of old_AB & 16 are then the index for enc_states

      if ( enc_value == old_enc_value ) {

     return;

   }

   if( enc_value == 255 ) {       // Original line

     enc_value = 0;

   }

   printf("enc_value = %3d, old_AB = %3d, old_enc_value = %3d\n\r",enc_value,old_AB,old_enc_value);  // debugging...

   printf(lcd_putc,"\fEncoder 0 = %d\n",enc_value);

   old_enc_value = enc_value;

   // set whatever variable you need to increment to enc_value here...

   }

//////////////////////////////////////////////////////////////////#int_TIMER0

void timer0_isr()

   {

      output_toggle(PIN_A2);     // let me know it's alive...

   }

//////////////////////////////////////////////////////////////////
void main(void) {
   port_b_pullups(true);

   setup_adc_ports(NO_ANALOGS);

   set_tris_b(255);

   input_b();

   ENABLE_INTERRUPTS(global);

   ENABLE_INTERRUPTS(INT_TIMER0);

   SETUP_TIMER_0(RTCC_INTERNAL | RTCC_DIV_32);
   printf("\n\r\rRotary Encoder Test 2\n\n\r");

   printf(lcd_putc,"\fRotary Encoder\nTest 2");

   delay_ms(1000);
   while (true)

   {

      encoder0Loop();

   }     // end of while loop

} // end of main

I have scoped the encoder and it is working properly; currently this runs through the loop endlessly, with no response to the encoder at all! Any help would be greatly appreciated, but no problem if you don’t want to!

Thanks,
Brad

By: oleg

oleg — Wed, 30 Dec 2009 23:32:27 +0000

Encoder’s A and B pins are connected to Atmega’s PORTC pins 0 and 1. The name for the whole port byte is PINC. The magic happens on line 33 . ‘PINC & 0×03′ clears upper 6 bits of whatever was read from PORTC leaving bits 0 and 1 intact. ‘old_AB |= ( PINC & 0×03 )’ generates an index for enc_states. This code would work on a PIC with almost no changes, the port name being the only one. You would need to have your encoder connected to 2 lower bits of a port, otherwise the code would become more complex.

By: Brad

Brad — Wed, 30 Dec 2009 22:56:46 +0000

I guess what I’m asking is, how do you read your encoder?? (Like you said, outputting the question clariefies it in your mind!)

By: Brad

Brad — Wed, 30 Dec 2009 22:44:54 +0000

Neat stuff, Oleg!

I’m trying to borrow your encoder routine to use in my PIC 18F4620… I’ve got a couple of questions, though.

In line 33, you AND PINC & 0×03, and then OR it with old_AB… what is PINC connected to? How to you get your encoder0PinA & B input values into enc_value? (I’m guessing here…)

Thanks for a great website and projects!