drybox-core/src/main.c

#include "common.h"
#include "bus/usart.h"
#include "bus/mosfet.h"
#include "bus/pwm.h"
#include "bus/i2c.h"

#include <avr/interrupt.h>

// TODO: Implement primary state machine for update loop.
// TODO: Migrate to ATMega 1284P-PU for 2nd 16-bit timer.
// TODO: Keep persistent TEMP and DEWP targets in EEPROM.
// TODO: Check thermistor conversion results /w thermometer.
// TODO: Implement optional CRC8 sensor measurement check.
// TODO: Use 18.432MHz quarz crystal, burn required fuses.
// TODO: Write an improved command parser (low priority).
// TODO: Proper error handling and recovery (after testing).

enum state_e
{
	S_IDLE,
	S_HEAT_UP,
	S_COOL_DOWN,
	S_DEHUMIDIFY
};

static enum state_e state;
static float temp, temp_target;
static float dewp, dewp_target;

static int Init(void)
{
	state = S_IDLE;

	// MOSFETS control things like the heating element
	// so they are the highest priority to initialize
	// to a default state via MOS_Init().

	MOS_Init();

	// The serial interface is required for output
	// functions like Info() and Error() and it uses
	// IRQs, so we need to initialize it as soon as
	// possible and make sure to enable interrupts.

	USART_Init();
	sei();

	Info("Initializing...");

	// The watchdog timer is clocked from a separate
	// on-chip oscillator which runs at 1 MHz. Eight
	// different clock cycle periods can be selected
	// to determine the reset period. If the reset
	// period expires, the chip resets and executes
	// from the reset vector.

	// The update loop must call WDT_Reset to reset
	// the timer, kind of like a dead man's switch
	// allowing us to detect infinite loops and any
	// other error that halts execution.

	if (WDT_HasTriggered())
		Info("Unexpected system reset.");

	WDT_Enable();
	WDT_SetTimeoutFlag(WDT2000); // 2 seconds

	// There is a possiblity to use interrupt signals
	// for I2C communication but only as one large
	// branching routine for the whole I2C system.
	// The blocking approach used right now is fine.

	I2C_Init();
	PWM_Init();

	MOS_Enable(MOS03); // Lights
	MOS_Enable(MOS01); // Peltier
	// MOS_Disable(MOS02); // Heating

	// Only FAN01 and FAN02 are receiving the correct
	// frequency (25 KHz) right now. The 16-bit timer on
	// the ATMega32A has two outputs so it would require
	// software PWM to have a variable frequency on PD7.

	// A simple implementation will take up around 30-50
	// percent of CPU time. Faster approaches are quite
	// complicated so it might be worth it to switch to
	// something like an ATmega328PB.

	PWM_SetValue(FAN01, 20); // Fan Peltier Hot side
	PWM_SetValue(FAN02, 50); // Fan Peltier Cold Side
	// PWM_SetValue(FAN03, 20); // Fan Heating

	// The I2C_SetChannel command changes the channel
	// setting of the PCA9546 I2C multiplexer. Any
	// command after it will be sent to the device
	// listening on that channel.

	I2C_SetChannel(AHT01);
	I2C_AHT20_Init();

	I2C_SetChannel(AHT02);
	I2C_AHT20_Init();

	I2C_SetChannel(AHT03);
	I2C_AHT20_Init();

	return 0;
}

static void Update(void)
{
	float t[3], rh[3];
	float adct[3];

	Info("Reading sensor values...");

	I2C_SetChannel(AHT01);
	I2C_AHT20_Read(&t[0], &rh[0]);

	I2C_SetChannel(AHT02);
	I2C_AHT20_Read(&t[1], &rh[1]);

	I2C_SetChannel(AHT03);
	I2C_AHT20_Read(&t[2], &rh[2]);

	adct[0] = I2C_ADS1115_ReadThermistor(ADS01);
	adct[1] = I2C_ADS1115_ReadThermistor(ADS02);
	adct[2] = I2C_ADS1115_ReadThermistor(ADS03);

	Info("T1=%.2fC, RH1=%.2f%%, ADCT1=%.2fC", t[0], rh[0], adct[0]);
	Info("T2=%.2fC, RH2=%.2f%%, ADCT2=%.2fC", t[1], rh[1], adct[1]);
	Info("T3=%.2fC, RH3=%.2f%%, ADCT3=%.2fC", t[2], rh[2], adct[2]);

	// TODO: Implement state machine
	// TODO: Handle serial commands

	switch (state) {
	case S_IDLE:
		break;
	case S_HEAT_UP:
		break;
	case S_COOL_DOWN:
		break;
	case S_DEHUMIDIFY:
		break;
	}

	UNUSED(temp);
	UNUSED(dewp);
	UNUSED(temp_target);
	UNUSED(dewp_target);
}

int main(void)
{
	Init();

	for (;;) {
		WDT_Reset();
		Update();
		WDT_Reset();
		Sleep(1000);
	}

	return 0;
}