Problem interfacing stepper motor with Atmega 32

Question

I have been trying to interface a bipolar stepper motor with an ATmega32 controller using AVR assembly, but it just keeps clicking without movement or just move back and forth in the same step. Here is the code:

    .include "m32def.inc"

    ; define motor pins         
    .equ A1              = PB0
    .equ A2              = PB1
    .equ B1              = PB2
    .equ B2              = PB3


    .cseg                       
    .org 0x00


     ser r16       
     out DDRB, r16          ;do not need to save r16


start:

     ; Step 1

     sbi PORTB, A1
     cbi PORTB, A2
     cbi PORTB, B1
     cbi PORTB, B2
     ldi delayMultiplier, 50
     rcall delay


     ; Step 2
     cbi PORTB, A1
     cbi PORTB, A2
     sbi PORTB, B1
     cbi PORTB, B2
     ldi delayMultiplier, 50
     rcall delay
     
     ; Step 3
     cbi PORTB, A1
     sbi PORTB, A2
     cbi PORTB, B1
     cbi PORTB, B2
     ldi delayMultiplier, 50
     rcall delay


     ; Step 4
     cbi PORTB, A1
     cbi PORTB, A2
     cbi PORTB, B1
     sbi PORTB, B2

      
     ldi delayMultiplier, 50
     rcall delay
     rjmp start






    .def delayMultiplier = r25

    .equ l1      = 20000


 delay:
      push r27
      push r26
      push r25
      

      
    
 loop2:
    
      ldi r26, LOW(l1)
      ldi r27, HIGH(l1)
      
loop1:
      sbiw r26, 1
      brne loop1

      dec delayMultiplier
      brne loop2

      
      pop r25
      pop r26
      pop r27


      ret

I tried some C code that does the same function and it kind of worked, but was still glitchy and behaved weirdly. It starts rotating then begin clicking a bit and eventually totally stopping.

 #include <avr/io.h>
    #define F_CPU 8000000L
    #include <util/delay.h>
    
   
    
    
    int main(void)
    {
        DDRB = 0xff;
        
        while (1) 
        {
            
         PORTB = 0x01;  //A1 high
         _delay_ms(500);
         PORTB = 0x02;  //B1 high
         _delay_ms(500);
         PORTB = 0x04;  //A2 high
         _delay_ms(500);
         PORTB = 0x08;  //B2 high
         _delay_ms(500);
        
            
            
        }
    }

lastly I tried it using an Arduino UNO, and for some reason is worked flawlessly

void setup() {
  // put your setup code here, to run once:
DDRB = 0xff;
}

void loop() {
  // put your main code here, to run repeatedly:

    PORTB = 0x01;  //A1 high
    delay(500);
    PORTB = 0x02;  //B1 high
    delay(500);
    PORTB = 0x04;  //A2 high
    delay(500);
    PORTB = 0x08;  //B2 high
    delay(500);

} 

it also worked with this code

int a1 = 7, a2 = 6, b1 = 5, b2 = 4;


void setup() {
  // put your setup code here, to run once:
pinMode(a1,OUTPUT);
pinMode(a2,OUTPUT);
pinMode(b1,OUTPUT);
pinMode(b2,OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(a1,HIGH);
digitalWrite(a2,LOW);
digitalWrite(b1,LOW);
digitalWrite(b2,LOW);

delay(100);

digitalWrite(a1,LOW);
digitalWrite(a2,LOW);
digitalWrite(b1,HIGH);
digitalWrite(b2,LOW);

delay(100);

digitalWrite(a1,LOW);
digitalWrite(a2,HIGH);
digitalWrite(b1,LOW);
digitalWrite(b2,LOW);

delay(100);

digitalWrite(a1,LOW);
digitalWrite(a2,LOW);
digitalWrite(b1,LOW);
digitalWrite(b2,HIGH);

delay(100);


}

Obviously I have no Idea what is going on so please advice.

Note that I am doing this for a university project so I have to do it using assembly.

Circuit Schematic:

Answer 1

You seem to have inconsistent pins, PORTs, and DDRs.

Your schematic seems to show the motor controller connected to chip PD0-3, but your working Arduino code sample seems to access PORTB. Then the second working Arduino code is accessing the PORTD pins (using their Arduino pin numbers).

Your non-working C code example seems to set the DDRD but then update the PORTB bits.

Lots of sloppy inconsistencies here, which will make it very hard to figure out what is happening.

Are you using the same hardware in all these examples?

I also see that in your schematic you are using PORTD pins that are also multiplexed with the serial port. If the serial port pins are enabled then the GPIO on this same pins is disabled. You do not show enabling the serial port in your ASM code, but again with everything so inconsistent it is hard to tell.

Clean everything up and report back with your results and I'm sure we can get everything working.

Answer 2

The assembly code can't use rcall to subroutine because the stack is not initialized. It also does not adhere to standard startup code with interrupt vectors, including a reset vector, at address 0, but it may not require that. Please see the datasheet or application notes for working examples of assembly code.