I have been playing with the UNO for a while now and now I have switched to the DUE. I have the following shield the can potentially control 4 DC motors.
http://arduino-direct.com/sunshop/index.php?l=product_detail&p=292
The shield comes with a library that is strictly for AVR Arduinos (everything but the DUE), so the library is useless. Trying to decypher the language, I understand that it is using a latch to trigger forward and reverse current (via shift register). I know where to send the PWM just not the control of direction...
http://yourduino.com/docs/Multi-MotorShieldSchematic.jpg
My previous designs required me to send states that would direct the polarity of the current to provide the reversing or forwarding of the motors. Now this shield uses a shift register and direct latch. This confusion along with my limited understand of ARM is making this difficult for me to understand.
Notice the "~_BV(a);" and "_BV(b);" and its variations that all polarity in the current.
From Library of Shield
- Code: Select all
void AF_DCMotor::run(uint8_t cmd) {
uint8_t a, b;
switch (motornum) {
case 1:
a = MOTOR1_A; b = MOTOR1_B; break;
case 2:
a = MOTOR2_A; b = MOTOR2_B; break;
case 3:
a = MOTOR3_A; b = MOTOR3_B; break;
case 4:
a = MOTOR4_A; b = MOTOR4_B; break;
default:
return;
}
switch (cmd) {
case FORWARD:
latch_state |= _BV(a);
latch_state &= ~_BV(b);
MC.latch_tx();
break;
case BACKWARD:
latch_state &= ~_BV(a);
latch_state |= _BV(b);
MC.latch_tx();
break;
case RELEASE:
latch_state &= ~_BV(a);
latch_state &= ~_BV(b);
MC.latch_tx();
break;
}
}
I hope this isnt to vague of a question. Please let me know if this is confusing.
Thanks,
Dan
