Handle PWM on pin PD4, PD5 and PD7

src/common.h

@@ -5,9 +5,13 @@
 
 #define BIT(n)            (0x1U << (n))
 #define UNUSED(s)         (void)(s)
+#define MAX(a, b)         ((a) > (b) ? (a) : (b))
+#define MIN(a, b)         ((a) < (b) ? (a) : (b))
+#define CLAMP(n, hi, lo)  (MIN(hi, MAX(n, lo)))
 
 void Info(const char *fmt, ...);
 void Error(const char *fmt, ...);
+double Clamp(double n, double upper, double lower);
 
 #include <util/delay.h>
 #define Sleep(ms) _delay_ms(ms)

src/common/common.c

@@ -1,6 +1,7 @@
 #include "common.h"
 #include "bus/usart.h"
 #include <stdio.h>
+#include <math.h>
 
 static void Puts(const char *str)
 {

src/main.c

@@ -5,6 +5,11 @@
 #include <avr/interrupt.h>
 #include <assert.h>
 
+// Minimum speed for Noctua fans is 20%
+#define FAN_01_MIN_DUTY 255 / 100 * 20
+#define FAN_02_MIN_DUTY 255 / 100 * 20
+#define HEATER_MIN_DUTY 0
+
 // ADS1115 (ADC)
 // PCA9546 (Multiplexer TWI)
 // ATH20 (3x)
@@ -26,6 +31,9 @@
 
 static void SetPinDefaults(void);
 static void SetTWIChannel(int channel);
+static void SetFan01Speed(int n);
+static void SetFan02Speed(int n);
+static void SetHeaterTemp(int n);
 
 int main(void)
 {
@@ -39,29 +47,18 @@ int main(void)
 	Info("Initializing...");
 	SetTWIChannel(0);
 
-	Sleep(500);
+	SetFan01Speed(51);
+	SetFan02Speed(51);
+	SetHeaterTemp(0);
+
+	for (;;) {
+		Info("PING");
+		Sleep(1000);
+	}
 
 	return 0;
 }
 
-static void SetPinDefaults(void)
-{
-	// Initialize Pin Outputs
-	// ======================
-
-	// PB0: MOSFET #1 (Peltier)
-	DDRB |= (1 << PB0);    // Out
-	PORTB &= ~(1 << PB0);  // Low
-
-	// PB1: MOSFET #2 (Heating)
-	DDRB |= (1 << PB1);    // Out
-	PORTB &= ~(1 << PB1);  // Low
-
-	// PB2: MOSFET #3 (Lights)
-	DDRB |= (1 << PB2);    // Out
-	PORTB &= ~(1 << PB2);  // Low
-}
-
 static void SetTWIChannel(int channel)
 {
 	unsigned char crb;
@@ -115,3 +112,107 @@ static void SetTWIChannel(int channel)
 
 	Info("TWI channel was switched to %d.", channel);
 }
+
+static void SetPinDefaults(void)
+{
+	// Initialize Pin Outputs
+	// ======================
+
+	// PB0: MOSFET #1 (Peltier)
+
+	DDRB |= BIT(PB0);    // Out
+	PORTB &= ~BIT(PB0);  // Low
+
+	// PB1: MOSFET #2 (Heating)
+
+	DDRB |= BIT(PB1);    // Out
+	PORTB &= ~BIT(PB1);  // Low
+
+	// PB2: MOSFET #3 (Lights)
+
+	DDRB |= BIT(PB2);    // Out
+	PORTB &= ~BIT(PB2);  // Low
+
+	// PD4: PWM Peltier Hot Side
+	// PD5: PWM Peltier Cold Side
+	// PD7: PWM Heating
+
+	DDRD |= BIT(PD4) | BIT(PD5) | BIT(PD7);
+
+        // Fast mode, 8-bit, non-inverting, no prescaling
+	TCCR1A = BIT(WGM10) | BIT(COM1A1);
+	TCCR1B = BIT(WGM12) | BIT(CS10);
+        TCCR2 = BIT(WGM20) | BIT(WGM21) | BIT(COM21) | BIT(CS20);
+
+	// PD4 OC1B (Timer/Counter1 Output CompareB Match Output)
+	OCR1A = 51; // Minimum speed for Noctua fans at 20% PWM
+
+	// PD5 OC1A (Timer/Counter1 Output CompareA Match Output)
+	OCR1B = 51; // Minimum speed for Noctua fans at 20% PWM
+
+	// PD7 OC2 (Timer/Counter2 Output Compare Match Output)
+	OCR2  = 0;  // XXX: Set heater low to turn off?
+
+	// TODO: Update documentation below from ATMega32A sheet...
+	// Had to skip the TCR0 timer and use TCR1 and TCR2 instead.
+
+	// TCCR0 8-bit Timer/Counter Register
+	// 7    6     5     4     3     2    1    0
+	// FOC0 WGM00 COM01 COM00 WGM01 CS02 CS01 CS00
+
+	// Waveform Generation Mode Bit
+	// Mode  WGM01  WGM00   Counter Mode
+	//    0      0      0   Normal
+	//    1      0      1   PWM Phase Correct
+	//    2      1      0   CTC
+	//    3      1      1   PWM Fast
+
+	// Compare Output Mode, Fast PWM Mode
+	// COM01  COM00   Description
+	//     0      0   Normal port operation, OC0 disconnected.
+	//     0      1   Reserved.
+	//     1      0   Clear OC0 on match, set OC0 at BOTTOM, (non-inverting mode).
+	//     1      1   Set OC0 on match, clear OC0 at BOTTOM, (inverting mode).
+
+	// Compare Output Mode, Phase Correct PWM Mode
+	// COM01  COM00   Description
+	//     0      0   Normal port operation, OC0 disconnected.
+	//     0      1   Reserved.
+	//     1      0   Clear OC0 on match when up-counting, set when downcounting.
+	//     1      1   Set OC0 on match when up-counting, clear when downcounting.
+
+	// Clock Select Bit
+	// CS02  CS01  CS00   Description
+	//    0     0     0   No clock source (Timer/Counter stopped).
+	//    0     0     1   clk I/O No prescaling
+	//    0     1     0   clk I/O /8 from prescaler
+	//    0     1     1   clk I/O /64 from prescaler
+	//    1     0     0   clk I/O /256 from prescaler
+	//    1     0     1   clk I/O /1024 from prescaler
+	//    1     1     0   External clock source on T0 pin. Clock on falling edge.
+	//    1     1     1   External clock source on T0 pin. Clock on rising edge.
+}
+
+static void SetFan01Speed(int n)
+{
+	n = CLAMP(n, 0xFF, FAN_01_MIN_DUTY);
+	Info("Setting FAN01 to PWM %d.", n);
+
+	OCR1B = (unsigned char) n; // PD4
+}
+
+static void SetFan02Speed(int n)
+{
+	n = CLAMP(n, 0xFF, FAN_02_MIN_DUTY);
+	Info("Setting FAN02 to PWM %d.", n);
+
+	OCR1A = (unsigned char) n; // PD5
+}
+
+static void SetHeaterTemp(int n)
+{
+	n = CLAMP(n, 0xFF, HEATER_MIN_DUTY);
+	Info("Setting HEATER to PWM %d.", n);
+
+	OCR2 = (unsigned char) n; // PD7
+}