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 Posted: Jul 26, 2012 - 07:36 AM |
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Joined: Mar 19, 2010
Posts: 52
Location: California
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I don't know if this is a hardware issue or software. So if its not hardware will a mod move it to the correct forum.
I have an ATmega1284P driving 2 L298 Dual Full Bridge Drivers on a custom circuit. Currently I am running 4 FA-130 motors. I am using general I/O's for the direction and 4 PWM pins to set the duty cycle output of the L298's.
My issue is that when I program the AVR to output the same PWM signal, not all the motors spin at the same rate. I am 98% sure my software is set properly. I am using timer1 and timer2, mostly because of hardware design, which are configured the same.
Does anyone have a solid place to start for trouble shooting.
Or tips, suggestions, incite. |
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I am not encumbered by the restraints of the adult mind.
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Posted: Jul 26, 2012 - 01:11 PM |
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Joined: Sep 04, 2002
Posts: 21249
Location: Orlando Florida
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| To be able to help, we need to see the schematic, and the c source. |
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Imagecraft compiler user
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Posted: Jul 26, 2012 - 06:02 PM |
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Joined: Mar 19, 2010
Posts: 52
Location: California
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I am using a 18.432 crystal. The PCB has been changed around aref and avcc to allow for internal voltage reference. And pins 1 and 15 on both L298 now have .5ohms 3 watt resistors to ground. I do not have a schematic but I do have my PCB design.
I know I do not have great comments so if I need to comment anything let me know.
Code:
void setup(void){
/** Timer1 Setup **/
TCCR1A |= (1 << WGM10) | (1 << COM1A1) | (1 << COM1B1);
TCCR1B |= (1 << CS10) | (1 << CS12);
/** Timer2 Setup **/
TCCR2A |= (1 << WGM20) | (1 << COM2A1) | (1 << COM2B1);
TCCR2B |= (1 << CS20) | (1 << CS21) | (1 << CS22);
}
void motor_output_on(){
DDRD |= (1 << DDD0) | (1 << DDD1) | (1 << DDD2) | (1 << DDD3) | (1 << DDD4) | (1 << DDD5) | (1 << DDD6) | (1 << DDD7);
DDRC |= (1 << DDC0) | (1 << DDC1) | (1 << DDC6) | (1 << DDC7);
}
void motor_output_off(){
DDRD &= ~(1 << DDD0) & ~(1 << DDD1) & ~(1 << DDD2) & ~(1 << DDD3) & ~(1 << DDD4) & ~(1 << DDD5) & ~(1 << DDD6) & ~(1 << DDD7);
DDRC &= ~(1 << DDC0) & ~(1 << DDC1) & ~(1 << DDC6) & ~(1 << DDC7);
}
void right_front(int speed, int direction){
if (direction == 0){ // Forward
OCR2A = speed;
PORTC |= (1 << DDC7); // C = H
PORTC &= ~(1 << DDC6); // D = L
} else if (direction == 1){ // Reverse
OCR2A = speed;
PORTC &= ~(1 << DDC7); // C = L
PORTC |= (1 << DDC6); // D = H
} else if (direction == 2){ // Fast Motor Stop
OCR2A = speed;
PORTC |= (1 << DDC6) | (1 << DDC7); // C = D
} else if (direction == 3){ // Free Running Motor Stop
OCR2A = 0; // C = X, D = X
}
}
void right_rear(int speed, int direction){
if (direction == 0){ // Forward
OCR2B = speed;
PORTC |= (1 << DDC0); // C = H
PORTC &= ~(1 << DDC1); // D = L
} else if (direction == 1){ // Reverse
OCR2B = speed;
PORTC &= ~(1 << DDC0); // C = L
PORTC |= (1 << DDC1); // D = H
} else if (direction == 2){ // Fast Motor Stop
OCR2B = speed;
PORTC |= (1 << DDC1) | (1 << DDC0); // C = D
} else if (direction == 3){ // Free Running Motor Stop
OCR2B = 0; // C = X, D = X
}
}
void left_front(int speed, int direction){
if (direction == 0){ // Forward
OCR1BL = speed;
PORTD |= (1 << DDD3); // C = H
PORTD &= ~(1 << DDD2); // D = L
} else if (direction == 1){ // Reverse
OCR1BL = speed;
PORTD &= ~(1 << DDD3); // C = L
PORTD |= (1 << DDD2); // D = H
} else if (direction == 2){ // Fast Motor Stop
OCR1BL = speed;
PORTD |= (1 << DDD2) | (1 << DDD3); // C = D
} else if (direction == 3){ // Free Running Motor Stop
OCR1BL = 0; // C = X, D = X
}
}
void left_rear(int speed, int direction){
if (direction == 0){ // Forward
OCR1AL = speed;
PORTD |= (1 << DDD1); // C = H
PORTD &= ~(1 << DDD0); // D = L
} else if (direction == 1){ // Reverse
OCR1AL = speed;
PORTD &= ~(1 << DDD1); // C = L
PORTD |= (1 << DDD0); // D = H
} else if (direction == 2){ // Fast Motor Stop
OCR1AL = speed;
PORTD |= (1 << DDD0) | (1 << DDD1); // C = D
} else if (direction == 3){ // Free Running Motor Stop
OCR1AL = 0; // C = X, D = X
}
}
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I am not encumbered by the restraints of the adult mind.
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Posted: Jul 27, 2012 - 03:18 AM |
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Joined: Feb 06, 2009
Posts: 832
Location: TN
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Could it be that Timer1 is a 16 bit timer, and Timer2 is 8 bit?
Perhaps using 16 bit values on Timer1 will help. Try setting the OCR1 high registers instead of the low. |
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It all starts with a mental vision.
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Posted: Jul 27, 2012 - 06:51 AM |
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Joined: Nov 22, 2002
Posts: 12035
Location: Tangent, OR, USA
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Also, if you are using PWM as a simple proportional drive, rather than stepping, the motor speed will be a function of the motor (varies some from one to the next), the supply voltage, the circuit losses, and the load.
Are you sure that both PWMs have the same duty cycle? Can you check with a scope?
Jim |
_________________
Jim Wagner
Oregon Research Electronics, Consulting Div.
Tangent, OR, USA
"The only thing standing between us and victory is defeat" P.G.Wodhouse in Wooster & Jeeves series
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