Add power save mode and send messages every 7.5s

weather-sensor/firmware/bme280_interface.c

@@ -21,10 +21,7 @@ int8_t Initialize_BME280(void)
 	uint8_t settings_sel;
 
 
-	/* Setup the SPI interface */
-	BME_CSN_DDR |= (1 << BME_CSN_PIN);
-	BME_CSN_PORT |= (1 << BME_CSN_PIN);
-
+	Set_BME280_Pins();
 
 	/* Sensor_0 interface over SPI with native chip select line */
 	deviceStructure.dev_id = 0;
@@ -51,6 +48,13 @@ int8_t Initialize_BME280(void)
 	return rslt;
 }
 
+void Set_BME280_Pins(void)
+{
+	/* Setup the SPI interface */
+	BME_CSN_DDR |= (1 << BME_CSN_PIN);
+	BME_CSN_PORT |= (1 << BME_CSN_PIN);
+}
+
 /* Get one measurement in forced mode */
 void BME280_Get_Measurement(struct bme280_data * data)
 {

weather-sensor/firmware/bme280_interface.h

@@ -10,6 +10,7 @@
 #define BME_CSN_PIN   PB2
 
 int8_t Initialize_BME280(void);
+void Set_BME280_Pins(void);
 void BME280_Get_Measurement(struct bme280_data * data);
 
 #endif

weather-sensor/firmware/main.c

@@ -1,4 +1,6 @@
 #include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/sleep.h>
 #include <util/delay.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -10,10 +12,6 @@
 #include "bme280_interface.h"
 #include "bme280_defs.h"
 
-//#define LED_DDR     DDRB        //DDRA, DDRB...
-//#define LED_PORT    PORTB       //PORTA, PORTB...
-//#define LED_PORTPIN PB0         //PA0, PA1..., PB0, PB1..., ...
-//#define time_off    8
 
 /* SPI: */
 /* TODO: move to spi.h */
@@ -22,14 +20,46 @@
 #define SPI_MOSI_PIN  PB3
 #define SPI_MISO_PIN  PB4
 
+/* Debug LED: */
+#define LED_DDR   DDRD
+#define LED_PORT  PORTD
+#define LED_PIN   PD3
 
 
 char bool_case = 0;
 int timer = 0;
 int timer_max = 0;
 
+volatile uint8_t cycle = 0;
+
+volatile uint8_t interruptCounter;
+volatile uint8_t executionFlag;
+
 
 void Initialize_SPI(void);
+void Enter_Power_Save_Mode(void);
+void Exit_Power_Save_Mode(void);
+
+
+/* TODO Notes for power saving:
+ * - Power-save-mode needed -> SM2...0 bits written to 011
+ * - Entering by issuing the SLEEP instruction -> What call in C?
+ *   - Before executing the SLEEP instruction, write bit SE of the SMCR to 1
+ * - Let Timer/Counter2 run with the necessary period and enable an interrupt.
+ *   -> The Global Interrupt Enable bit in SREG has to be set.
+ * - asynchronous/synchronous clock source?
+ * - When waking up
+ *   - Set PRR bits for needed peripherals
+ * - 
+ */
+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. */
+}
 
 int main (void)
 {
@@ -38,7 +68,10 @@ int main (void)
 //	uint8_t registerContent[5];
 //	char registerContentString[30];
 //	uint8_t lengthRead;
+	uint8_t temp = 0;
 
+	/* Enable the debug LED */
+	LED_DDR |= (1 << LED_PIN);
 
 	/* Initialize the SPI */
 	Initialize_SPI();
@@ -52,21 +85,119 @@ int main (void)
 
 	/* Initialize the BME280 */
 	Initialize_BME280();
+	Set_Up_Power_Save_Mode();
 
 
+	/* 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)
 	{
-		BME280_Get_Measurement(&sensorData);
-		NRF24L01_Send_Message((uint8_t*)&sensorData, sizeof(sensorData));
-		_delay_ms(1000);
+		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);
+			NRF24L01_Send_Message((uint8_t*)&sensorData, sizeof(sensorData));
+
+			if (temp == 0)
+			{
+				LED_PORT |= (1 << LED_PIN);
+				temp = 1;
+			}
+			else
+			{
+				temp = 0;
+				LED_PORT &= ~(1 << LED_PIN);
+			}
+
+			cycle = 0;
+		}
+		else
+		{
+			cycle ++;
+		}
 	}
 }
 
 void Initialize_SPI(void)
 {
+	/* TODO: move to spi.h */
 	/* Set MOSI and SCK output, all others input */
 	SPI_DDR = (1<<SPI_MOSI_PIN)|(1<<SPI_SCK_PIN);
 	/* Enable SPI, Master, set clock rate fck/16 */
 	SPCR = (1<<SPE)|(1<<MSTR);
 }
+
+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
+}

weather-sensor/firmware/nrf24l01.c

@@ -24,15 +24,7 @@ void Initialize_NRF24L01(void)
 	CONFIG_REGISTER configRegisterContents = {.byte = 0x0};
 
 	/* Configure the AVR pins for the nrf24l01 */
-	/* Set up the NRF24L01 */
-	NRF_CE_DDR |= (1 << NRF_CE_PIN);
-	NRF_CSN_DDR |= (1 << NRF_CSN_PIN);
-
-	/* Set the chip select pin to not selected */
-	NRF_CSN_PORT |= (1 << NRF_CSN_PIN);
-
-	/* Ensure that the CE pin is set to 0*/
-	NRF_CE_PORT &= ~(1 << NRF_CE_PIN);
+	Set_NRF24L01_Pins();
 
 	/* Wait more than 10.3 ms to make sure the nrf24l01 is running */
 	_delay_ms(11);
@@ -48,6 +40,19 @@ void Initialize_NRF24L01(void)
 	/* The NRF24L01 is now in the mode Standby-I */
 }
 
+void Set_NRF24L01_Pins(void)
+{
+	/* Set up the NRF24L01 */
+	NRF_CE_DDR |= (1 << NRF_CE_PIN);
+	NRF_CSN_DDR |= (1 << NRF_CSN_PIN);
+
+	/* Set the chip select pin to not selected */
+	NRF_CSN_PORT |= (1 << NRF_CSN_PIN);
+
+	/* Ensure that the CE pin is set to 0*/
+	NRF_CE_PORT &= ~(1 << NRF_CE_PIN);
+}
+
 void Configure_Transmission(void)
 {
 	FEATURE_REGISTER featureRegisterContents = {.byte = 0x0};
@@ -138,6 +143,10 @@ void NRF24L01_Send_Message(uint8_t *buffer, uint8_t length)
 	do
 	{
 		_delay_ms(1);
+		/* TODO: instead of polling the status register use the IRQ to spawn an interrupt as the
+		 * constant polling may induce transmission errors:
+		 * https://forum.mysensors.org/topic/10452/nrf24l01-communication-failure-root-cause-and-solution
+		 */
 		statusRegisterContents.byte = Read_NRF_Status_Register();
 
 		if (statusRegisterContents.bits.TX_DS == 1)

weather-sensor/firmware/nrf24l01.h

@@ -13,6 +13,7 @@
 #define NRF_CSN_PIN   PB6
 
 void Initialize_NRF24L01(void);
+void Set_NRF24L01_Pins(void);
 void Configure_Transmission(void);
 uint8_t Read_NRF_Status_Register(void);
 uint8_t Read_NRF_Register(uint8_t address, uint8_t * registerContents);