Start working on system initialization

src/main.c

@@ -3,15 +3,33 @@
 #include "bus/twi.h"
 
 #include <avr/interrupt.h>
+#include <assert.h>
+
+// ADS1115 (ADC)
+// PCA9546 (Multiplexer TWI)
+// ATH20 (3x)
+// BMP280 (3x)
+
+// PB0 Mosfet 1 Peltier
+// PB1 Mosfet 2 Heating
+// PB2 Mosfet 3 Lights
+
+// PD4 PWM Peltier Hot Side
+// PD5 PWM Peltier Cold Side
+// PD7 PWM Heating
+
+// PC0 TWI Multiplexer SCL
+// PC1 TWI Multiplexer SDA
+
+// PD0 Serial USART RX
+// PD1 Serial USART TX
+
+static void SetPinDefaults(void);
+static void SetTWIChannel(int channel);
 
 int main(void)
 {
-	char crb;
-
-	// ADS1115 (ADC)
-	// PCA9546 (Multiplexer TWI)
-	// ATH20 (3x)
-	// BMP280 (3x)
+	SetPinDefaults();
 
 	USART_Init();
 	TWI_Init();
@@ -19,11 +37,42 @@ int main(void)
 	sei();
 
 	Info("Initializing...");
+	SetTWIChannel(0);
+
+	Sleep(500);
+
+	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;
+
+	assert(channel >= 0);
+	assert(channel <= 3);
 
 	// PCA9546 I2C Multiplexer
 	// =======================
 
-	TWI_Stop();
+	Info("Switching TWI channel to %d...", channel);
 
 	// Excerpts taken from the PCA9546A datasheet:
 	// https://www.ti.com/lit/ds/symlink/pca9546a.pdf
@@ -45,12 +94,14 @@ int main(void)
 
 	//  7  6  5  4   |   3   2   1   0
 	//  X  X  X  X   |  B3  B2  B1  B0
-	//               |  CHANNEL_______
+	//  UNUSED____   |  CHANNEL_______
 
-	crb = 0x01; //  Channel 0  |  00000001
-	//  = 0x02  //  Channel 1  |  00000010
-	//  = 0x04  //  Channel 2  |  00000100
-	//  = 0x08  //  Channel 3  |  00001000
+	crb = (1 << channel);
+
+	// crb = 0x01; //  Channel 0  |  00000001
+	// crb = 0x02  //  Channel 1  |  00000010
+	// crb = 0x04  //  Channel 2  |  00000100
+	// crb = 0x08  //  Channel 3  |  00001000
 
 	TWI_Write(crb);
 
@@ -62,8 +113,5 @@ int main(void)
 	TWI_Wait_ACK();
 	TWI_Stop();
 
-	Info("Switched to TWI channel 0.");
-	Sleep(500);
-
-	return 0;
+	Info("TWI channel was switched to %d.", channel);
 }