Update module 'pwm' to run on atmega1284p hardware

src/bus/pwm.c

@@ -1,23 +1,15 @@
 #include "common.h"
 #include "bus/pwm.h"
 
+// TODO: Add documentation for timer3: TCCR3A, TCCR3B, etc.
+
 int PWM_Init(void)
 {
 	// PD4: PWM NF-12 Fan Peltier Hot Side
 	// PD5: PWM NF-A8 Fan Peltier Cold Side
 	// PD7: PWM NF-R8 Fan Heating Element
 
-	// ATMega32A does not have more than two outputs for the
-	// 16-bit timer and the other 8-bit timers don't have modes
-	// where the value of TOP can be changed. We can only get
-	// 25 KHz with software PWM on this chip as far as I know.
-
-	// The 328P would allow us to use OCR2A as top but with
-	// 8-bit this gives us a really low duty step size of 2.5%.
-	// Ideal would be two 16-bit timers with two outputs each.
-
 	DDRD |= BIT(PD4) | BIT(PD5) | BIT(PD7);
-	// PORTD &= ~BIT(PD7); // Turn off PD7
 
 	// TCCR1A Timer1 Control Register A
 	// 7       6       5       4       3      2      1      0
@@ -90,18 +82,13 @@ int PWM_Init(void)
 	TCCR1B = BIT(WGM12) | BIT(WGM13) | BIT(CS10);
 	ICR1 = PWM_CYCLE_TOP; // 8000 MHz / 25000 KHz
 
+	TCCR3A = BIT(WGM31) | BIT(COM3A1) | BIT(COM3B1);
+	TCCR3B = BIT(WGM32) | BIT(WGM33) | BIT(CS30);
+	ICR3 = PWM_CYCLE_TOP; // 8000 MHz / 25000 KHz
+
 	OCR1B = FAN01_MIN_DUTY; // PD4
 	OCR1A = FAN02_MIN_DUTY; // PD5
-
-	// TIMER2: Fast mode, non-inverting, top=0xFF, prescale /8
-	// TOP set to 8000000 (f_cpu) / 8 (prescale) / 25000 (f_pwm) - 1
-
-	TCCR2 = BIT(WGM20) | BIT(WGM21) | BIT(COM21) | BIT(CS21);
-	OCR2 = 255; // XXX: OCR2A=TOP OCR2B=duty
-
-	// TCCR2 = 0; // Normal operation
-	// OCR2 = FAN03_MIN_DUTY; // PD7
-	// PORTD &= ~BIT(PD7);  // Low
+	OCR2A = FAN03_MIN_DUTY; // PD7
 
 	return 0;
 }
@@ -125,6 +112,6 @@ void PWM_SetValue(int port, int value)
 	switch (port) {
 	case PD4: OCR1B = n; break;
 	case PD5: OCR1A = n; break;
-	case PD7: OCR2  = n; break;
+	case PD7: OCR2A = n; break;
 	}
 }