smart-home/weather-sensor/firmware/main.c

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <util/delay.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>

#include "led.h"
#include "spi.h"
#include "nrf24l01.h"
#include "nrf24l01_definitions.h"
#include "bme280_interface.h"
#include "bme280_defs.h"
#include "pin_programming.h"
#include "crc.h"
#include "encryption.h"



uint8_t ownId;
const uint8_t encryptionKey[16] = {0x9e, 0x37, 0x79, 0xb9, 0x9b, 0x97, 0x73, 0xe9, 0xb9, 0x79, 0x37, 0x9e, 0x6b, 0x69, 0x51, 0x56}; /* TODO: use exernal file with the keys */
uint64_t salt;

char bool_case = 0;
int timer = 0;
int timer_max = 0;

volatile uint8_t cycle = 0;

volatile bool nrfInterruptRaised;

volatile uint8_t interruptCounter;
volatile uint8_t executionFlag;


static uint8_t messageBuffer[PACKET_LENGTH];
static PACKET * packet = (PACKET*) messageBuffer;


void Enter_Power_Save_Mode(void);
void Exit_Power_Save_Mode(void);


bool Send_Get_Salt_Message(PACKET * packet, uint64_t salt); //TODO: put into own file
bool Read_Salt_Message(PACKET * packet, uint64_t * salt);

void Set_Up_Power_Save_Mode(void);
void Enter_Power_Save_Mode(void);


ISR(TIMER2_COMPA_vect)
{
	/* Do nothing as the interrupt is only used to wake up the MCU. */
}

ISR(PCINT2_vect)
{
	nrfInterruptRaised = true;
}

int main (void)
{
	struct bme280_data sensorData;
	uint16_t crc;
	bool saltReceived = false;

	/* Enable the debug LED */
	LED_DDR |= (1 << LED_PIN);

	/* Get the own ID */
	Configure_Pin_Programming_Pins();
	ownId = Get_Own_Identifier();

	/* Initialize the SPI */
	Initialize_SPI();

	/* Initialize the nrf24l01 */
	Initialize_NRF24L01();
	// The NRF24L01 is now in the mode Standby-I.

	/* Configure the transmission parameters (Enhanced ShockBurst)*/
	Configure_Transmission(ownId);

	/* Initialize the BME280 */
	Initialize_BME280();
	Set_Up_Power_Save_Mode();

	/* Initialize the salt */
	salt = 0x0ull;
	salt |= ownId;


	/* TODO: Request a salt from the base station:
	 * - loop as long as no reply from the base station was received:
	 *   - send the packet that requests the salt
	 *   - if no ack is received for the packet go direclty to sleep for 100 ms
	 *   - if no salt is received within 100 ms send the message again
	 *   - keep the LED on for the duration to allow the user to see that the device is ready for operation.
	 */
	LED_PORT |= (1 << LED_PIN);
	do
	{
		if (Send_Get_Salt_Message(packet, salt) == true)
		{
			memset(messageBuffer, 0x0F, 32);
			if (NRF24L01_Receive_Message(messageBuffer, 100 /*ms*/) == true)
			{
				_delay_ms(10);
				saltReceived = Read_Salt_Message(packet, &salt);
			}
		}
		else
		{
			/* TODO: enter power save mode instead to make the battery life longer */
			_delay_ms(100);
		}
	} while (saltReceived == false);
	LED_PORT &= ~(1 << LED_PIN);

	salt &= 0xFFFFFFFFFFFFFF00ull;
	salt |= ownId;


	/* Delay the change of the operating frequency by the function Enter_Power_Save_Mode for the
	 * first function pass. If it is changed before the ISP can flash the MCU the clocks of the ISP
	 * and MCU are mismatched and the flashing will fail.
	 */
	_delay_ms(500);

	while(1)
	{
		Enter_Power_Save_Mode(); // The MCU enters the Power Save Mode here.
		Exit_Power_Save_Mode(); // The MCU exits the Power Save Mode here.

		if (cycle == 0) // TODO cycle == 7 to execute this every 60 s
		{
			/* Re-Initialize the peripherals */
			Set_BME280_Pins();
			Set_NRF24L01_Pins();

			/* Get measurement and send it */
			BME280_Get_Measurement(&sensorData);


			/* TODO: put the following into a Send_Report function */
			memset((uint8_t*)packet, 0, PACKET_LENGTH); //Reinitialize the buffer with zeros

			salt &= ~(1ull<<63);
			packet->salt = salt;
			packet->payload.reportData.packetIdentifier.elementCount = 3;
			packet->payload.reportData.packetIdentifier.packetType = PACKET_TYPE_REPORT;

			/* Fill in the payload */
			packet->payload.reportData.valueTypeTemperature = VALUE_TYPE_TEMPERATURE;
			packet->payload.reportData.temperature = sensorData.temperature/10;
			packet->payload.reportData.valueTypePressure = VALUE_TYPE_PRESSURE;
			packet->payload.reportData.pressure = sensorData.pressure;
			packet->payload.reportData.valueTypeHumidity = VALUE_TYPE_HUMIDITY;
			packet->payload.reportData.humidity = sensorData.humidity * 100/1024;

			/* Calculate the CRC */
			crc = Calculate_Crc(packet->payload.buffer, PACKET_PAYLOAD_BUFFER_LENGTH);
			packet->crc = crc;

			/* Encrypt the packet */
			/* TODO: 
			 * - increment the salt for every packet
			 * - Receive salt from the base station
			 */
			Encrypt((uint32_t*) packet->payload.buffer,
			        PACKET_PAYLOAD_BUFFER_LENGTH + sizeof(crc),
			        salt, (uint32_t*) encryptionKey);

			NRF24L01_Send_Message((uint8_t*)packet, PACKET_LENGTH);

			/* Increment salt */
			salt += (1 << 8);

			LED_PORT |= (1 << LED_PIN);
			_delay_ms(100); /* TODO: only for debugging, remove this later! */
			LED_PORT &= ~(1 << LED_PIN);

			cycle = 0;
		}
		else
		{
			cycle ++;
		}
	}
}

void Set_Up_Power_Save_Mode(void)
{
	// Disable Brown-Out-Detection by setting the BODLEVEL 2:0 Fuses to 0b111 (should be default)
	// Disable the on-chip debug system by setting the DWEN Fuse to 1 (should be default)

	/* Disable some unused peripherals that are not used during operation of the weather station: */
	// The ADC is turned off by default
	ACSR &= ~(1<<ACD); // Analog comperator
	ACSR &= ~(1<<ACIE); // The interrupt bit has to be cleared after switchin of the analog comperator
	/*
	 * The Internal voltager reference is automatically disabled if the BOD, ADC and Voltage
	 * Reference are disabled
	 */

	/* Set up Timer/Counter2 */
	PRR &= ~(1<<PRTIM2); // Enable the timer 2 in the Power Reduction Register

	TCCR2A |= (1<<COM2A1)|(1<<COM2A0)|(1<<WGM21); // Set the timer to ClearTimer on Compare Match with output compare mode for channel A
	/* There is a problem: The maximum time until the counter 2 overflows is 262ms at the nominal
	 * core frquency of 1MHz and a timer prescaler of 1024.
	 * This can be attenuated by lowering the system frequency to 31.25 kHz via the clock prescaler
	 * (CLKPS3...0) of the register CLKPR. This gives a overflow time of 8.3s.
	 * The cycle time of one minute can thus be accomplished by setting the output compare register
	 * to 229. This spawns an interrupt every 7.5s which means the operation has to be executed
	 * every 8 interrupt calls.
	 */

	TCCR2B |= (1<<CS22)|(1<<CS21)|(1<<CS20); // Set the timer prescaler to 1/1024
	OCR2A = 229; // TODO: calculate this number from the wanted cycle time and the timer frequency.

	TIMSK2 |= (1<<OCIE2A); // Enable the Output Compare Match A Interrupt.

	/* Enable global interrupts: */
	sei();
}

void Enter_Power_Save_Mode(void)
{
	PRR |= (1<<PRTWI) | (1<<PRTIM0) | (1<<PRTIM1) | (1<<PRSPI) | (1<<PRUSART0) | (1<<PRADC); /* Only timer 2 is needed for wake-up interrupt */

	/* Set the clock prescaler for a frequency of 32.25 kHz*/
	CLKPR = (1<<CLKPCE);
	CLKPR = (1<<CLKPS3);

	TCNT2 = 0;// Reset timer 2
	TIMSK2 |= (1<<OCIE2A); // Enable the Output Compare Match A Interrupt.


	set_sleep_mode(SLEEP_MODE_PWR_SAVE);
	sleep_mode();
}

void Exit_Power_Save_Mode(void)
{
	TIMSK2 &= ~(1<<OCIE2A); // Disable the Output Compare Match A Interrupt.

	/* Set the normal operating frequency of 1 MHz */
	CLKPR = (1<<CLKPCE);
	CLKPR = (1<<CLKPS1) | (1<<CLKPS0);

	PRR &= ~(1<<PRSPI); // Enable SPI
	Initialize_SPI(); // reinitalize SPI
}

bool Send_Get_Salt_Message(PACKET * packet, uint64_t salt) //TODO: put into own file
{
	bool success = false;
	uint16_t crc;

	memset((uint8_t*)packet, 0, PACKET_LENGTH); //Reinitialize the buffer with zeros

	salt &= ~(1ull<<63); /* Set the most significant bit to 0 to indicate a packet from the device to the base station */

	packet->salt = salt;
	packet->payload.reportData.packetIdentifier.elementCount = 0;
	packet->payload.reportData.packetIdentifier.packetType = PACKET_TYPE_GET_SALT;

	/* Calculate the CRC */
	crc = Calculate_Crc(packet->payload.buffer, PACKET_PAYLOAD_BUFFER_LENGTH);
	packet->crc = crc;

	Encrypt((uint32_t*) packet->payload.buffer,
	        PACKET_PAYLOAD_BUFFER_LENGTH + sizeof(crc),
	        salt,
	        (uint32_t*) encryptionKey);

	success = NRF24L01_Send_Message((uint8_t*)packet, PACKET_LENGTH);


	return success;
}

bool Read_Salt_Message(PACKET * packet, uint64_t * salt)
{
	uint16_t crcRemainder = 0xFFFF;
	uint64_t baseStationSalt = 0x0;


	/* TODO: check that the packet originated from the base station by checking the id */

	baseStationSalt = packet->salt;
	Decrypt((uint32_t*)packet->payload.buffer,
	        PACKET_PAYLOAD_BUFFER_LENGTH + sizeof(packet->crc),
	        baseStationSalt,
	        (uint32_t*) encryptionKey);

	crcRemainder = Calculate_Crc(packet->payload.buffer,
	                             PACKET_PAYLOAD_BUFFER_LENGTH + sizeof(packet->crc));
	if (crcRemainder != 0)
	{
		return false;
	}

	if ((packet->payload.saltData.packetIdentifier.packetType != PACKET_TYPE_SALT) ||
	    (packet->payload.saltData.packetIdentifier.elementCount != 0))
	{
		return false;
	}

	memcpy((uint8_t*)salt, packet->payload.saltData.salt, 7);
	*salt = (*salt) << 8;

	return true;
}