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BMP280 datasheet.pdf
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Apache License
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README.md
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# zh_avr_bmp280_sensor # AVR firmware for BMP280 wireless sensor (nRF24L01+)
AVR firmware for BMP280 wireless sensor (nRF24L01+). ## Features
1. Wireless sensor firmware for ATMega168/328 microcontrollers with BMP280 temperature and pressure sensor.
2. Power consumption in sleep mode approximately 5 uA using Power-down mode.
3. Transmits device identifier, battery voltage, temperature, and pressure readings on each measurement cycle.
4. Battery measurement through internal ADC with 1.1 V bandgap reference.
5. Wake-up from Power-down mode by watchdog timer interrupt with ~8 second interval.
6. Supports ATMega168, ATMega168P, ATMega168PB, ATMega328, ATMega328P, and ATMega328PB.
7. Hardware TWI (I2C) for BMP280 communication on PORTC pins PC4 (SDA) and PC5 (SCL).
## Attention
1. A compatible RF Gateway is required to receive and process transmitted packets.
2. Changing gateway address or channel requires reflashing the microcontroller.
3. The watchdog timer interval is fixed at ~8 seconds; the sensor transmits every 38 ticks (~5 minutes).
## Using
In an existing PlatformIO project, run the following command to install the firmware:
```bash
cd your_project
git clone https://github.com/aZholtikov/zh_avr_bmp280_sensor
```
platformio.ini
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[env:ATmega168]
platform = atmelavr
board = ATmega168
board_build.mcu = atmega168
board_build.f_cpu = 8000000L
framework = arduino
upload_protocol = usbasp
board_fuses.lfuse = 0xE2
board_fuses.hfuse = 0xDF
board_fuses.efuse = 0x07
upload_flags =
-Pusb
-e
lib_deps =
https://github.com/aZholtikov/zh_rf_config
[env:ATmega168P]
platform = atmelavr
board = ATmega168P
board_build.mcu = atmega168p
board_build.f_cpu = 8000000L
framework = arduino
upload_protocol = usbasp
board_fuses.lfuse = 0xE2
board_fuses.hfuse = 0xDF
board_fuses.efuse = 0x07
upload_flags =
-Pusb
-e
lib_deps =
https://github.com/aZholtikov/zh_rf_config
[env:ATmega168PB]
platform = atmelavr
board = ATmega168PB
board_build.mcu = atmega168pb
board_build.f_cpu = 8000000L
framework = arduino
upload_protocol = usbasp
board_fuses.lfuse = 0xE2
board_fuses.hfuse = 0xDF
board_fuses.efuse = 0x07
upload_flags =
-Pusb
-e
lib_deps =
https://github.com/aZholtikov/zh_rf_config
[env:ATmega328]
platform = atmelavr
board = ATmega328
board_build.mcu = atmega328
board_build.f_cpu = 8000000L
framework = arduino
upload_protocol = usbasp
board_fuses.lfuse = 0xE2
board_fuses.hfuse = 0xDF
board_fuses.efuse = 0x07
upload_flags =
-Pusb
-e
lib_deps =
https://github.com/aZholtikov/zh_rf_config
[env:ATmega328P]
platform = atmelavr
board = ATmega328P
board_build.mcu = atmega328p
board_build.f_cpu = 8000000L
framework = arduino
upload_protocol = usbasp
board_fuses.lfuse = 0xE2
board_fuses.hfuse = 0xDF
board_fuses.efuse = 0x07
upload_flags =
-Pusb
-e
lib_deps =
https://github.com/aZholtikov/zh_rf_config
[env:ATmega328PB]
platform = atmelavr
board = ATmega328PB
board_build.mcu = atmega328pb
board_build.f_cpu = 8000000L
framework = arduino
upload_protocol = usbasp
board_fuses.lfuse = 0xE2
board_fuses.hfuse = 0xDF
board_fuses.efuse = 0x07
upload_flags =
-Pusb
-e
lib_deps =
https://github.com/aZholtikov/zh_rf_config
src/main.c
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#include "avr/io.h"
#include "avr/interrupt.h"
#include "avr/sleep.h"
#include "avr/wdt.h"
#include "util/delay.h"
#include "stdbool.h"
#include "math.h"
#include "zh_rf_config.h"
#if defined(__AVR_ATmega328PB__)
#ifndef SPCR
#define SPCR SPCR0
#endif
#ifndef SPDR
#define SPDR SPDR0
#endif
#ifndef SPSR
#define SPSR SPSR0
#endif
#ifndef SPE
#define SPE SPE0
#endif
#ifndef MSTR
#define MSTR MSTR0
#endif
#ifndef SPR0
#define SPR0 SPR00
#endif
#ifndef SPIF
#define SPIF SPIF0
#endif
#ifndef TWBR
#define TWBR TWBR0
#endif
#ifndef TWCR
#define TWCR TWCR0
#endif
#ifndef TWSR
#define TWSR TWSR0
#endif
#ifndef TWDR
#define TWDR TWDR0
#endif
#endif
#define GATEWAY_CHANNEL 120
#define GATEWAY_ADDRESS 0xDDEEFF
#define DEVICE_ID 6
#define WDT_WAKE_COUNT 38
#define ZH_TWI_TWBR 32
#define NRF_CMD_W_REGISTER 0x20
#define NRF_CMD_W_TX_PAYLOAD 0xA0
#define NRF_CMD_FLUSH_TX 0xE1
#define NRF_CMD_NOP 0xFF
#define NRF_REG_CONFIG 0x00
#define NRF_REG_EN_AA 0x01
#define NRF_REG_EN_RXADDR 0x02
#define NRF_REG_SETUP_AW 0x03
#define NRF_REG_SETUP_RETR 0x04
#define NRF_REG_RF_CH 0x05
#define NRF_REG_RF_SETUP 0x06
#define NRF_REG_STATUS 0x07
#define NRF_REG_RX_ADDR_P0 0x0A
#define NRF_REG_TX_ADDR 0x10
#define NRF_CONFIG_MASK_RX_DR 0x40
#define NRF_CONFIG_EN_CRC 0x08
#define NRF_CONFIG_PWR_UP 0x02
#define NRF_STATUS_RX_DR 0x40
#define NRF_STATUS_TX_DS 0x20
#define NRF_STATUS_MAX_RT 0x10
#define BMP280_ADDR 0x76
#define BMP280_REG_ID 0xD0
#define BMP280_REG_RESET 0xE0
#define BMP280_REG_CTRL_MEAS 0xF4
#define BMP280_REG_CONFIG 0xF5
#define BMP280_REG_DATA 0xF7
#define BMP280_REG_CALIB00 0x88
/**
* @brief Initialize the watchdog timer for periodic wake-up.
*
* Configures the watchdog timer with a ~8 second interval using prescaler
* values WDP3 and WDP0, enables the watchdog interrupt, and clears the
* MCU reset flag. The watchdog interrupt service routine increments
* wdt_wake_count on each trigger.
*/
static void zh_wdt_init(void);
/**
* @brief Initialize the hardware TWI (I2C) peripheral.
*
* Configures PC4 (SDA) and PC5 (SCL) as inputs with pull-up enabled,
* sets the TWI bit-rate register (TWBR) and enables the TWI module
* in master mode. The hardware TWI is used for communication with
* the BMP280 sensor.
*/
static void zh_i2c_init(void);
/**
* @brief Wait for the TWI interrupt flag with a timeout.
*
* Polls the TWINT bit in TWCR until it is set or the 16-bit timeout
* counter expires. Returns true if the transfer completed successfully.
*
* @return true if TWINT was set before the timeout expired
* @return false on timeout
*/
static bool zh_i2c_wait(void);
/**
* @brief Generate a TWI start (or repeated start) condition.
*
* Asserts START and waits for completion, then verifies the status code
* (0x08 = start transmitted, 0x10 = repeated start transmitted).
*
* @return true when the start condition was acknowledged by the controller
* @return false on timeout or unexpected status
*/
static bool zh_i2c_start(void);
/**
* @brief Generate a TWI stop condition.
*
* Asserts STOP and waits (bounded by a timeout loop) until the TWSTO
* bit is cleared by hardware.
*/
static void zh_i2c_stop(void);
/**
* @brief Write one byte on the TWI bus and return the ACK status.
*
* Loads TWDR, triggers transmission and checks the TWI status code.
* Returns true when the slave acknowledges the byte (statuses 0x18,
* 0x28 for data transmit, 0x40 for SLA+R transmit).
*
* @param data Byte to transmit
*
* @return true if the slave acknowledged the byte
* @return false on timeout or NACK
*/
static bool zh_i2c_write(uint8_t data);
/**
* @brief Read one byte from the TWI bus and send an ACK after reading.
*
* Enables the acknowledge bit (TWEA), triggers the read cycle and
* returns the contents of TWDR. Returns 0xFF on timeout.
*
* @return Received byte
*/
static uint8_t zh_i2c_read_ack(void);
/**
* @brief Read one byte from the TWI bus and send a NACK after reading.
*
* Disables the acknowledge bit, triggers the read cycle and returns
* the contents of TWDR. Returns 0xFF on timeout.
*
* @return Received byte
*/
static uint8_t zh_i2c_read_nack(void);
/**
* @brief Write a register value to the BMP280 sensor over TWI.
*
* Initiates a TWI transaction with the BMP280 address, writes the
* register address followed by the value, and stops the bus. A delay
* of 2 ms is applied after the write for the sensor's internal timing.
*
* @param reg Register address to write
* @param value Value to write to the register
*
* @return true on success
* @return false if the start/stop condition or any byte transfer failed
*/
static bool zh_bmp280_write_reg(uint8_t reg, uint8_t value);
/**
* @brief Read multiple bytes from a BMP280 register over TWI.
*
* Performs a repeated-start transaction: writes the register address
* then reads the specified number of bytes, sending ACK for each byte
* except the last one, where a NACK is sent.
*
* @param reg Register address to read from
* @param buf Pointer to the buffer where the data will be stored (must not be NULL)
* @param len Number of bytes to read
*
* @return true on success
* @return false if any start condition or byte transfer failed
*/
static bool zh_bmp280_read_reg(uint8_t reg, uint8_t *buf, uint8_t len);
/**
* @brief Initialize the BMP280 sensor and read calibration data.
*
* Verifies the device ID, performs a soft reset, reads all calibration
* registers (33 bytes total), and configures humidity and filter settings.
* A 100 ms delay is applied after power-up before reading the device ID.
*
* @return true if the sensor is present and initialized successfully
* @return false if the device ID does not match or a register operation fails
*/
static bool zh_bmp280_init(void);
/**
* @brief Read raw sensor data from the BMP280.
*
* Configures the sensor for a measurement cycle, waits for conversion
* to complete, then reads 8 bytes of raw data and unpacks the pressure,
* and temperature ADC values.
*
* @param temperature Pointer to store the raw temperature ADC value (must not be NULL)
* @param pressure Pointer to store the raw pressure ADC value (must not be NULL)
*
* @return true on success
* @return false if the register write or read operation fails
*/
static bool zh_bmp280_read(int32_t *temperature, int32_t *pressure);
/**
* @brief Compensate raw temperature using Bosch calibration coefficients.
*
* Applies the 32-bit compensation algorithm defined in the BMP280 datasheet
* using calibration data read during initialization. The result is stored
* in BMP280_t_fine for use by the pressure and humidity compensators.
*
* @param adc_t Raw temperature ADC value
*
* @return Compensated temperature in degrees Celsius
*/
static float zh_bmp280_compensate_temperature(int32_t adc_t);
/**
* @brief Compensate raw pressure using Bosch calibration coefficients.
*
* Applies the 32-bit compensation algorithm defined in the BMP280 datasheet.
* The result is in Pascals. Returns zero if the denominator becomes zero.
*
* @param adc_p Raw pressure ADC value
*
* @return Compensated pressure in Pascals
*/
static float zh_bmp280_compensate_pressure(int32_t adc_p);
/**
* @brief Initialize the SPI peripheral for nRF24L01 communication.
*
* Configures PB2 (CE), PB3 (MISO), and PB5 (SCK) as output, sets PB2
* high, and configures the SPI peripheral for master mode with Fck/2
* clock divider. The SS pin is not managed by hardware and must be
* controlled manually via PB2.
*/
static void zh_spi_init(void);
/**
* @brief Transfer one byte over SPI and return the received byte.
*
* Writes the data to SPDR, waits for the transfer complete flag, then
* returns the contents of SPDR.
*
* @param data Byte to transmit
*
* @return Received byte
*/
static uint8_t zh_spi_transfer(uint8_t data);
/**
* @brief Initialize the nRF24L01 radio module.
*
* Configures the CE and IRQ pins, sets up TX and RX addresses, configures
* the channel, enables automatic retransmission, and enables CRC. The
* module is left in standby mode with RX and TX interrupts masked.
*/
static void zh_nrf24_init(void);
/**
* @brief Transmit a packet via the nRF24L01 module.
*
* Powers up the radio, flushes the TX FIFO, writes the payload, asserts
* CE high to trigger transmission, waits for the IRQ line, then deasserts
* CE. The status register is read, cleared, and the TX FIFO is flushed
* again after transmission.
*
* @param buf Pointer to the data buffer to transmit (must not be NULL)
* @param size Number of bytes to transmit
*/
static void zh_nrf24_send(uint8_t *buf, uint8_t size);
/**
* @brief Write a payload to the nRF24L01 using a write command.
*
* Asserts CSN low, transfers the command byte, writes the payload data,
* then deasserts CSN. Returns the status register value.
*
* @param cmd SPI command byte for payload write
* @param buf Pointer to the data buffer (must not be NULL)
* @param count Number of bytes to write
*
* @return SPI status register value after the command byte
*/
static uint8_t zh_nrf24_write_buffer(uint8_t cmd, uint8_t *buf, uint8_t count);
/**
* @brief Write a single byte to an nRF24L01 register.
*
* Asserts CSN low, transfers the register address ORed with the write
* command mask, writes the value, then deasserts CSN.
*
* @param reg Register address
* @param val Value to write
*
* @return SPI status register value after the command byte
*/
static uint8_t zh_nrf24_write_register(uint8_t reg, uint8_t val);
/**
* @brief Write a buffer of data to an nRF24L01 register block.
*
* Asserts CSN low, transfers the register address ORed with the write
* command mask, writes each byte from the buffer, then deasserts CSN.
*
* @param reg Register address for the block
* @param buf Pointer to the data buffer (must not be NULL)
* @param count Number of bytes to write
*
* @return SPI status register value after the command byte
*/
static uint8_t zh_nrf24_write_buff_register(uint8_t reg, uint8_t *buf, uint8_t count);
/**
* @brief Send a command to the nRF24L01 without a data payload.
*
* Asserts CSN low, transfers the command byte, then deasserts CSN.
* Used for commands such as FLUSH_TX, FLUSH_RX, and NOP.
*
* @param cmd Command byte to send
*
* @return SPI status register value after the command byte
*/
static uint8_t zh_nrf24_send_command(uint8_t cmd);
/**
* @brief Measure the battery voltage using the AVR ADC.
*
* Configures the ADC with the internal 1.1 V reference and selects the
* 1.1 V bandgap input. Takes two conversions and returns the average
* as a voltage value. Returns zero if the ADC reading is zero.
*
* @return Battery voltage in volts
*/
static float zh_get_battery_voltage(void);
static volatile uint8_t wdt_wake_count = 0;
static uint8_t bmp280_calib[24] = {0};
static int32_t bmp280_t_fine = 0;
static bool bmp280_present = false;
zh_rf_sensor_transmitted_data_t transmitted_data = {DEVICE_ID, ZH_RF_SENSOR_BMP280, 0, 0, 0, 0, 0};
int main(void)
{
cli();
zh_i2c_init();
bmp280_present = zh_bmp280_init();
zh_spi_init();
zh_nrf24_init();
zh_wdt_init();
set_sleep_mode(SLEEP_MODE_PWR_DOWN);
sei();
int32_t adc_t = 0;
int32_t adc_p = 0;
if (bmp280_present == true)
{
if (zh_bmp280_read(&adc_t, &adc_p) == true)
{
transmitted_data.battery_voltage = (int16_t)lroundf(zh_get_battery_voltage() * 100.0);
transmitted_data.value_1 = (int16_t)lroundf(zh_bmp280_compensate_temperature(adc_t));
transmitted_data.value_2 = (int16_t)lroundf(zh_bmp280_compensate_pressure(adc_p) * 0.00750062);
zh_nrf24_send((uint8_t *)&transmitted_data, sizeof(transmitted_data));
}
else
{
bmp280_present = false;
}
}
for (;;)
{
sleep_enable();
sleep_cpu();
sleep_disable();
if (wdt_wake_count >= WDT_WAKE_COUNT)
{
wdt_wake_count = 0;
if (bmp280_present == false)
{
bmp280_present = zh_bmp280_init();
}
if (bmp280_present == true)
{
if (zh_bmp280_read(&adc_t, &adc_p) == true)
{
transmitted_data.battery_voltage = (int16_t)lroundf(zh_get_battery_voltage() * 100.0);
transmitted_data.value_1 = (int16_t)lroundf(zh_bmp280_compensate_temperature(adc_t));
transmitted_data.value_2 = (int16_t)lroundf(zh_bmp280_compensate_pressure(adc_p) * 0.00750062);
zh_nrf24_send((uint8_t *)&transmitted_data, sizeof(transmitted_data));
}
else
{
bmp280_present = false;
}
}
}
}
return 0;
}
static void zh_wdt_init(void)
{
cli();
wdt_reset();
MCUSR &= ~(1 << WDRF);
WDTCSR |= (1 << WDCE) | (1 << WDE);
WDTCSR = (1 << WDIE) | (1 << WDP3) | (1 << WDP0);
sei();
}
ISR(WDT_vect)
{
WDTCSR |= (1 << WDIE);
++wdt_wake_count;
}
static void zh_i2c_init(void)
{
DDRC &= ~((1 << PC4) | (1 << PC5));
PORTC |= (1 << PC4) | (1 << PC5);
TWSR = 0x00;
TWBR = ZH_TWI_TWBR;
TWCR = (1 << TWEN);
}
static bool zh_i2c_wait(void)
{
uint16_t timeout = 65535;
while (!(TWCR & (1 << TWINT)))
{
if (--timeout == 0)
{
return false;
}
}
return true;
}
static bool zh_i2c_start(void)
{
TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
if (zh_i2c_wait() == false)
{
return false;
}
uint8_t status = TWSR & 0xF8;
return (status == 0x08 || status == 0x10);
}
static void zh_i2c_stop(void)
{
TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
uint16_t timeout = 1000;
while ((TWCR & (1 << TWSTO)) && --timeout)
{
}
}
static bool zh_i2c_write(uint8_t data)
{
TWDR = data;
TWCR = (1 << TWINT) | (1 << TWEN);
if (zh_i2c_wait() == false)
{
return false;
}
uint8_t status = TWSR & 0xF8;
return (status == 0x18 || status == 0x28 || status == 0x40);
}
static uint8_t zh_i2c_read_ack(void)
{
TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWEA);
if (zh_i2c_wait() == false)
{
return 0xFF;
}
return TWDR;
}
static uint8_t zh_i2c_read_nack(void)
{
TWCR = (1 << TWINT) | (1 << TWEN);
if (zh_i2c_wait() == false)
{
return 0xFF;
}
return TWDR;
}
static bool zh_bmp280_write_reg(uint8_t reg, uint8_t value)
{
if (zh_i2c_start() == false)
{
zh_i2c_stop();
return false;
}
if (zh_i2c_write(BMP280_ADDR << 1) == false)
{
zh_i2c_stop();
return false;
}
if (zh_i2c_write(reg) == false)
{
zh_i2c_stop();
return false;
}
if (zh_i2c_write(value) == false)
{
zh_i2c_stop();
return false;
}
zh_i2c_stop();
_delay_ms(2);
return true;
}
static bool zh_bmp280_read_reg(uint8_t reg, uint8_t *buf, uint8_t len)
{
if (zh_i2c_start() == false)
{
zh_i2c_stop();
return false;
}
if (zh_i2c_write(BMP280_ADDR << 1) == false)
{
zh_i2c_stop();
return false;
}
if (zh_i2c_write(reg) == false)
{
zh_i2c_stop();
return false;
}
if (zh_i2c_start() == false)
{
zh_i2c_stop();
return false;
}
if (zh_i2c_write((BMP280_ADDR << 1) | 1) == false)
{
zh_i2c_stop();
return false;
}
for (uint8_t i = 0; i < len; ++i)
{
buf[i] = (i == len - 1) ? zh_i2c_read_nack() : zh_i2c_read_ack();
}
zh_i2c_stop();
return true;
}
static bool zh_bmp280_init(void)
{
_delay_ms(100);
uint8_t id = 0;
if (zh_bmp280_read_reg(BMP280_REG_ID, &id, sizeof(id)) == false || id != 0x58)
{
return false;
}
if (zh_bmp280_write_reg(BMP280_REG_RESET, 0xB6) == false)
{
return false;
}
_delay_ms(10);
if (zh_bmp280_read_reg(BMP280_REG_CALIB00, bmp280_calib, 24) == false)
{
return false;
}
if (zh_bmp280_write_reg(BMP280_REG_CONFIG, 0x00) == false)
{
return false;
}
return true;
}
static bool zh_bmp280_read(int32_t *temperature, int32_t *pressure)
{
if (zh_bmp280_write_reg(BMP280_REG_CTRL_MEAS, 0x25) == false)
{
return false;
}
_delay_ms(10);
uint8_t raw[6] = {0};
if (zh_bmp280_read_reg(BMP280_REG_DATA, raw, sizeof(raw)) == false)
{
return false;
}
*pressure = (int32_t)(((uint32_t)raw[0] << 12) | ((uint32_t)raw[1] << 4) | (raw[2] >> 4));
*temperature = (int32_t)(((uint32_t)raw[3] << 12) | ((uint32_t)raw[4] << 4) | (raw[5] >> 4));
return true;
}
static float zh_bmp280_compensate_temperature(int32_t adc_t)
{
int32_t dig_t1 = (int32_t)(uint16_t)(bmp280_calib[1] << 8 | bmp280_calib[0]);
int32_t dig_t2 = (int16_t)(bmp280_calib[3] << 8 | bmp280_calib[2]);
int32_t dig_t3 = (int16_t)(bmp280_calib[5] << 8 | bmp280_calib[4]);
int32_t var1 = ((((adc_t >> 3) - (dig_t1 << 1))) * dig_t2) >> 11;
int32_t var2 = (((((adc_t >> 4) - dig_t1) * ((adc_t >> 4) - dig_t1)) >> 12) * dig_t3) >> 14;
bmp280_t_fine = var1 + var2;
return (float)((bmp280_t_fine * 5 + 128) >> 8) / 100.0;
}
static float zh_bmp280_compensate_pressure(int32_t adc_p)
{
int32_t dig_p1 = (int32_t)(uint16_t)(bmp280_calib[7] << 8 | bmp280_calib[6]);
int32_t dig_p2 = (int16_t)(bmp280_calib[9] << 8 | bmp280_calib[8]);
int32_t dig_p3 = (int16_t)(bmp280_calib[11] << 8 | bmp280_calib[10]);
int32_t dig_p4 = (int16_t)(bmp280_calib[13] << 8 | bmp280_calib[12]);
int32_t dig_p5 = (int16_t)(bmp280_calib[15] << 8 | bmp280_calib[14]);
int32_t dig_p6 = (int16_t)(bmp280_calib[17] << 8 | bmp280_calib[16]);
int32_t dig_p7 = (int16_t)(bmp280_calib[19] << 8 | bmp280_calib[18]);
int32_t dig_p8 = (int16_t)(bmp280_calib[21] << 8 | bmp280_calib[20]);
int32_t dig_p9 = (int16_t)(bmp280_calib[23] << 8 | bmp280_calib[22]);
int32_t var1 = (((int32_t)bmp280_t_fine) >> 1) - 64000;
int32_t var2 = (((var1 >> 2) * (var1 >> 2)) >> 11) * dig_p6;
var2 = var2 + ((var1 * dig_p5) << 1);
var2 = (var2 >> 2) + (((int32_t)dig_p4) << 16);
var1 = (((dig_p3 * (((var1 >> 2) * (var1 >> 2)) >> 13)) >> 3) + (((int32_t)dig_p2 * var1) >> 1)) >> 18;
var1 = ((((32768 + var1)) * dig_p1) >> 15);
if (var1 == 0)
{
return 0.0;
}
uint32_t p = (((uint32_t)(((int32_t)1048576) - adc_p) - (var2 >> 12))) * 3125;
if (p < 0x80000000)
{
p = (p << 1) / ((uint32_t)var1);
}
else
{
p = (p / (uint32_t)var1) * 2;
}
var1 = (((int32_t)dig_p9) * ((int32_t)(((p >> 3) * (p >> 3)) >> 13))) >> 12;
var2 = (((int32_t)(p >> 2)) * ((int32_t)dig_p8)) >> 13;
return (float)((int32_t)p + ((var1 + var2 + dig_p7) >> 4));
}
static void zh_spi_init(void)
{
DDRB |= (1 << PB2) | (1 << PB3) | (1 << PB5);
PORTB |= (1 << PB2);
SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR0);
}
static uint8_t zh_spi_transfer(uint8_t data)
{
SPDR = data;
while ((SPSR & (1 << SPIF)) == 0)
{
}
return SPDR;
}
static void zh_nrf24_init(void)
{
_delay_ms(100);
DDRB |= (1 << PB1);
PORTB &= ~(1 << PB1);
DDRD &= ~(1 << PD2);
PORTD |= (1 << PD2);
uint64_t gateway_address = GATEWAY_ADDRESS;
zh_nrf24_write_register(NRF_REG_CONFIG, 0x00);
zh_nrf24_write_register(NRF_REG_EN_AA, 0x01);
zh_nrf24_write_register(NRF_REG_EN_RXADDR, 0x01);
zh_nrf24_write_register(NRF_REG_SETUP_AW, 0x01);
zh_nrf24_write_register(NRF_REG_SETUP_RETR, 0xFF);
zh_nrf24_write_register(NRF_REG_RF_CH, GATEWAY_CHANNEL);
zh_nrf24_write_register(NRF_REG_RF_SETUP, 0x26);
zh_nrf24_write_buff_register(NRF_REG_TX_ADDR, (uint8_t *)&gateway_address, 3);
zh_nrf24_write_buff_register(NRF_REG_RX_ADDR_P0, (uint8_t *)&gateway_address, 3);
zh_nrf24_write_register(NRF_REG_STATUS, NRF_STATUS_RX_DR | NRF_STATUS_TX_DS | NRF_STATUS_MAX_RT);
zh_nrf24_write_register(NRF_REG_CONFIG, NRF_CONFIG_MASK_RX_DR | NRF_CONFIG_EN_CRC);
}
static void zh_nrf24_send(uint8_t *buf, uint8_t size)
{
zh_nrf24_write_register(NRF_REG_CONFIG, NRF_CONFIG_MASK_RX_DR | NRF_CONFIG_EN_CRC | NRF_CONFIG_PWR_UP);
_delay_ms(5);
zh_nrf24_send_command(NRF_CMD_FLUSH_TX);
zh_nrf24_write_buffer(NRF_CMD_W_TX_PAYLOAD, buf, size);
PORTB |= (1 << PB1);
uint8_t count = 0;
while ((PIND & (1 << PD2)) != 0)
{
if (++count > 100)
{
break;
}
_delay_ms(1);
}
PORTB &= ~(1 << PB1);
uint8_t status = zh_nrf24_send_command(NRF_CMD_NOP);
zh_nrf24_write_register(NRF_REG_STATUS, status);
zh_nrf24_send_command(NRF_CMD_FLUSH_TX);
zh_nrf24_write_register(NRF_REG_CONFIG, NRF_CONFIG_MASK_RX_DR | NRF_CONFIG_EN_CRC);
}
static uint8_t zh_nrf24_write_buffer(uint8_t cmd, uint8_t *buf, uint8_t count)
{
PORTB &= ~(1 << PB2);
uint8_t status = zh_spi_transfer(cmd);
while (count-- != 0)
{
zh_spi_transfer(*(buf++));
}
PORTB |= (1 << PB2);
return status;
}
static uint8_t zh_nrf24_write_register(uint8_t reg, uint8_t val)
{
PORTB &= ~(1 << PB2);
uint8_t status = zh_spi_transfer(reg | NRF_CMD_W_REGISTER);
zh_spi_transfer(val);
PORTB |= (1 << PB2);
return status;
}
static uint8_t zh_nrf24_write_buff_register(uint8_t reg, uint8_t *buf, uint8_t count)
{
return zh_nrf24_write_buffer((reg | NRF_CMD_W_REGISTER), buf, count);
}
static uint8_t zh_nrf24_send_command(uint8_t cmd)
{
PORTB &= ~(1 << PB2);
uint8_t status = zh_spi_transfer(cmd);
PORTB |= (1 << PB2);
return status;
}
static float zh_get_battery_voltage(void)
{
ADMUX = (1 << REFS0) | (1 << MUX3) | (1 << MUX2) | (1 << MUX1);
ADCSRA = (1 << ADEN) | (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0);
_delay_ms(10);
ADCSRA |= (1 << ADSC);
while (ADCSRA & (1 << ADSC))
{
}
ADCSRA |= (1 << ADSC);
while (ADCSRA & (1 << ADSC))
{
}
uint16_t adc = ADCL;
adc |= (uint16_t)ADCH << 8;
ADCSRA &= ~(1 << ADEN);
if (adc == 0)
{
return 0.0;
}
return (1024.0 * 1.1) / (float)adc;
}
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# Описание компонента zh_avr_bmp280_sensor
## Общие сведения
**zh_avr_bmp280_sensor** — прошивка для AVR-микроконтроллеров ATMega168/328, реализующая беспроводной датчик климата на базе датчика BMP280 и трансивера nRF24L01+.
Компонент работает в режиме глубокого сна (Power-down), просыпается по таймеру (watchdog), измеряет температуру и давление на датчике BMP280 (интерфейс I2C) и передаёт на шлюз пакет с идентификатором устройства и уровнем заряда батареи.
### Основные возможности
1. **Сверхнизкое энергопотребление** — около 5 мкА в режиме сна.
2. **Измерение климата** — температура и атмосферное давление датчиком BMP280 по шине I2C.
3. **Передача уровня заряда батареи** — измерение напряжения через внутренний АЦП с опорным напряжением 1,1 В.
4. **Работа по протоколу nRF24L01+** — передача через SPI, адресная доставка на шлюз.
5. **Поддержка нескольких МК** — ATMega168/168P/168PB/328/328P/328PB.
6. **Пробуждение по watchdog-таймеру** — WDT с интервалом ~8 секунд, цикл работы каждые `WDT_WAKE_COUNT` (38) прерываний ≈ 5 минут.
7. **Автономная работа** — не требует внешних подтягивающих резисторов.
---
## Внутреннее устройство
### Структура данных
Компонент не использует динамическое выделение памяти и сложные структуры данных. Все данные передаются как массив `int16_t` фиксированной длины.
#### Формат передаваемого пакета
Пакет формируется в глобальной переменной `transmitted_data` типа `zh_rf_sensor_transmitted_data_t` из внешней библиотеки `zh_rf_config` и передаётся побайтово как массив байтов (`sizeof` структуры — 14 байт).
| Поле | Тип | Описание |
| ------ | ----- | ---------- |
| `id` | `int16_t` | Идентификатор устройства (`DEVICE_ID = 6`) |
| `type` | `int16_t` | Тип устройства (`ZH_RF_SENSOR_BMP280`) |
| `value_1` | `int16_t` | Температура (°C, например 25 = 25 °C) |
| `battery_voltage` | `int16_t` | Напряжение батареи × 100 (например, 330 = 3.30 В) |
| `value_2` | `int16_t` | Давление (мм рт. ст.) |
| `value_3` | `int16_t` | Зарезервировано (равно 0) |
| `value_4` | `int16_t` | Зарезервировано (равно 0) |
Тип устройства задаётся значением перечисления `ZH_RF_SENSOR_BMP280` из библиотеки `zh_rf_config`.
### Конфигурационные макросы
| Макрос | Значение | Описание |
| -------- | ---------- | ---------- |
| `GATEWAY_CHANNEL` | `120` | Радиоканал шлюза |
| `GATEWAY_ADDRESS` | `0xDDEEFF` | 3-байтовый адрес шлюза |
| `DEVICE_ID` | `6` | Уникальный идентификатор устройства |
| `WDT_WAKE_COUNT` | `38` | Количество прерываний WDT до пробуждения (≈ 5 минут) |
| `ZH_TWI_TWBR` | `32` | Значение регистра TWBR для задания скорости аппаратного TWI |
| `BMP280_ADDR` | `0x76` | 7-битный адрес датчика BMP280 на шине I2C |
### Управление памятью
Компонент не использует динамическую память. Все данные хранятся в статической области и регистрах микроконтроллера. Глобальная переменная `transmitted_data` объявлена как глобальная (не `static`) и заполняется при инициализации (идентификатор и тип). В цикле обновляются все поля данных: `battery_voltage`, `value_1` (температура), `value_2` (давление). Массив калибровки `bmp280_calib` размером 24 байта хранит калибровочные коэффициенты датчика.
---
## API (интерфейс)
Все функции являются `static` и доступны только внутри модуля `main.c`.
### Инициализация
| Функция | Описание |
| --------- | ---------- |
| `zh_wdt_init()` | Инициализация watchdog-таймера (~8 сек, прерывание WDT_vect) для периодического пробуждения |
| `zh_i2c_init()` | Инициализация аппаратного TWI (I2C) на пинах PC4 (SDA), PC5 (SCL), TWBR = 32 |
| `zh_bmp280_init()` | Инициализация датчика BMP280: проверка CHIP_ID (0x58), сброс, чтение калибровки (24 байта) |
| `zh_spi_init()` | Инициализация аппаратного SPI в режиме мастера (Fosc/2) |
| `zh_nrf24_init()` | Инициализация трансивера nRF24L01+ в режим передачи |
### Измерение
| Функция | Описание |
| ------- | -------- |
| `zh_get_battery_voltage()` | Измерение напряжения батареи через внутренний АЦП с опорой 1,1 В (две конверсии, усреднение) |
### Чтение данных BMP280
| Функция | Описание |
| --------- | ---------- |
| `zh_bmp280_read()` | Чтение 6 сырых байт из BMP280 и распаковка ADC значений температуры и давления |
| `zh_bmp280_compensate_temperature()` | Компенсация сырой температуры по калибровочным коэффициентам (результат в °C) |
| `zh_bmp280_compensate_pressure()` | Компенсация сырого давления по калибровочным коэффициентам (результат в Па) |
### Передача данных
| Функция | Описание |
| ------- | -------- |
| `zh_nrf24_send()` | Передача буфера через nRF24L01+: Power Up, `FLUSH_TX`, `W_TX_PAYLOAD`, импульс CE, ожидание IRQ с таймаутом 100 мс, сброс статуса |
### Низкоуровневые SPI-операции
| Функция | Описание |
| --------- | ---------- |
| `zh_spi_transfer()` | Обмен одного байта по SPI (полный дуплекс) |
| `zh_nrf24_write_register()` | Запись одного байта в регистр nRF24L01+ |
| `zh_nrf24_write_buff_register()` | Запись многобайтового буфера в регистр nRF24L01+ |
| `zh_nrf24_write_buffer()` | Запись буфера данных с указанной командой (CSN управляется вручную через PB2) |
| `zh_nrf24_send_command()` | Отправка однобайтовой команды и чтение статуса |
### Низкоуровневые TWI-операции (аппаратный I2C)
| Функция | Описание |
| --------- | ---------- |
| `zh_i2c_wait()` | Ожидание флага `TWINT` с таймаутом 65535 итераций (возвращает false при зависании шины) |
| `zh_i2c_start()` | Генерация стартового (или повторного стартового) условия, проверка статусов `0x08`/`0x10` |
| `zh_i2c_stop()` | Генерация стоп-условия с ограниченным ожиданием сброса бита `TWSTO` |
| `zh_i2c_write()` | Передача одного байта через `TWDR`, проверка статусов ACK (`0x18`, `0x28`, `0x40`) |
| `zh_i2c_read_ack()` | Чтение байта из `TWDR` с подтверждением ACK (возвращает `0xFF` при таймауте) |
| `zh_i2c_read_nack()` | Чтение последнего байта из `TWDR` без подтверждения NACK (возвращает `0xFF` при таймауте) |
### Служебные TWI-функции BMP280
| Функция | Описание |
| --------- | ---------- |
| `zh_bmp280_write_reg()` | Запись одного байта в регистр BMP280 (start, адрес, регистр, данные, stop, задержка 2 мс) |
| `zh_bmp280_read_reg()` | Чтение нескольких байт из регистров BMP280 (repeated-start, ACK/NACK) |
---
## Потокобезопасность
Компонент работает на bare-metal AVR без RTOS. Единственная точка синхронизации — ISR watchdog-таймера (`ISR(WDT_vect)`), которая увеличивает `wdt_wake_count` (объявлен как `static volatile uint8_t`). Главный цикл проверяет этот счётчик после выхода из сна. Атомарная запись одного байта на AVR гарантирует отсутствие состояний гонки при инкременте. Весь остальной обмен с периферией (I2C, SPI, АЦП) выполняется последовательно в главном цикле.
---
## Алгоритмы
### Алгоритм инициализации BMP280
- Задержка 100 мс после включения.
- Проверка `CHIP_ID` (регистр `BMP280_REG_ID`, ожидается `0x58`).
- Сброс записью `0xB6` в регистр `BMP280_REG_RESET`.
- Задержка 10 мс после сброса.
- Чтение калибровочных коэффициентов: 24 байта из `BMP280_REG_CALIB00` (массив `bmp280_calib`).
- Конфигурация измерения: `ctrl_meas = 0x25` (temp/pressure oversampling x16, forced mode).
### Алгоритм компенсации BMP280
Сырые ADC-значения пересчитываются в физические величины по алгоритмам производителя из datasheet BMP280.
- **Температура**: `zh_bmp280_compensate_temperature()` — вычисляет `bmp280_t_fine` (используется для давления), возвращает результат в °C. Формула: `((bmp280_t_fine * 5 + 128) >> 8) / 100.0`. Деление на `dig_t1` не выполняется.
- **Давление**: `zh_bmp280_compensate_pressure()` — возвращает результат в Па. При `var1 == 0` (знаменатель ноль) возвращает 0.0.
### Алгоритм аппаратного TWI
- Инициализация: `TWSR = 0x00` (предделитель 1), `TWBR = ZH_TWI_TWBR` (32), включение модуля битом `TWEN`. Скорость: `F_CPU / (16 + 2·TWBR·prescaler)` ≈ 100 кГц при 8 МГц.
- Стартовое/повторное стартовое условие: установка `TWSTA`, ожидание `TWINT`, проверка статуса (`0x08` — START, `0x10` — REPEATED START).
- Передача байта: запись в `TWDR`, сброс `TWINT`, ожидание завершения, проверка статусов подтверждения (`0x18`/`0x28` — данные, `0x40` — адрес чтения).
- Приём байта: установка `TWEA` для всех байт кроме последнего, чтение `TWDR` после `TWINT`.
- Останов: установка `TWSTO`, ограниченное ожидание (1000 итераций) сброса бита аппаратно.
- Обработка ошибок: каждая операция возвращает `false` при таймауте ожидания или неверном статусе, вызывающая сторона выполняет `zh_i2c_stop()`.
### Алгоритм передачи через nRF24L01+
- Переход в Power Up (бит `PWR_UP` в CONFIG).
- Ожидание 5 мс (время стартования осциллятора).
- Очистка TX FIFO командой `FLUSH_TX`.
- Загрузка полезной нагрузки командой `W_TX_PAYLOAD`.
- Импульс CE длительностью 20 мкс для запуска передачи.
- Ожидание завершения по пину IRQ (PD2) с таймаутом 100 мс.
- Сброс флагов статуса, очистка FIFO, переход в Power Down.
### Алгоритм сна и пробуждения
- Инициализация WDT: прерывание по таймауту ~8 секунд (`WDP3 | WDP0`), без сброса MCU.
- ISR `WDT_vect`: увеличивает `wdt_wake_count`, заново включает бит `WDIE`.
- Главный цикл: переход в Power-down (`sleep_cpu()`). После пробуждения проверяется `wdt_wake_count >= WDT_WAKE_COUNT` (38 × 8 с ≈ 5 минут).
- При достижении порога: обнуление счётчика, повторная инициализация BMP280 (если датчик недоступен), чтение показаний и передача пакета через nRF24L01+.
- Первое измерение выполняется сразу после инициализации перед входом в цикл.
---
## Примеры использования
### Типовой цикл работы (main)
```c
int main(void)
{
cli();
zh_i2c_init();
bmp280_present = zh_bmp280_init();
zh_spi_init();
zh_nrf24_init();
zh_wdt_init();
set_sleep_mode(SLEEP_MODE_PWR_DOWN);
sei();
int32_t adc_t = 0;
int32_t adc_p = 0;
if (bmp280_present == true)
{
if (zh_bmp280_read(&adc_t, &adc_p) == true)
{
transmitted_data.battery_voltage = (int16_t)lroundf(zh_get_battery_voltage() * 100.0);
transmitted_data.value_1 = (int16_t)lroundf(zh_bmp280_compensate_temperature(adc_t));
transmitted_data.value_2 = (int16_t)lroundf(zh_bmp280_compensate_pressure(adc_p) * 0.00750062);
zh_nrf24_send((uint8_t *)&transmitted_data, sizeof(transmitted_data));
}
else
{
bmp280_present = false;
}
}
for (;;)
{
sleep_enable();
sleep_cpu();
sleep_disable();
if (wdt_wake_count >= WDT_WAKE_COUNT)
{
wdt_wake_count = 0;
if (bmp280_present == false)
{
bmp280_present = zh_bmp280_init();
}
if (bmp280_present == true)
{
if (zh_bmp280_read(&adc_t, &adc_p) == true)
{
transmitted_data.battery_voltage = (int16_t)lroundf(zh_get_battery_voltage() * 100.0);
transmitted_data.value_1 = (int16_t)lroundf(zh_bmp280_compensate_temperature(adc_t));
transmitted_data.value_2 = (int16_t)lroundf(zh_bmp280_compensate_pressure(adc_p) * 0.00750062);
zh_nrf24_send((uint8_t *)&transmitted_data, sizeof(transmitted_data));
}
else
{
bmp280_present = false;
}
}
}
}
return 0;
}
```
### Изменение конфигурации под другое устройство
```c
// Измените идентификатор для нового устройства
#define DEVICE_ID 7 // Уникальный ID в сети
#define GATEWAY_CHANNEL 120
#define GATEWAY_ADDRESS 0xDDEEFF
// Тип устройства задаётся перечислением ZH_RF_SENSOR_BMP280
```
### Подключение по SPI и I2C (схема выводов)
```c
// Назначение пинов AVR:
// nRF24L01+ (SPI):
// PB2 -> CSN (управление SPI-селектом, выход)
// PB3 -> MOSI (назначается аппаратным SPI)
// PB5 -> SCK (назначается аппаратным SPI)
// PB1 -> CE (управление передачей, выход)
// PD2 -> IRQ (вход, активный низкий, с подтяжкой к VCC)
// BMP280 (I2C, аппаратный TWI):
// PC4 -> SDA (аппаратный TWI, pull-up)
// PC5 -> SCL (аппаратный TWI, pull-up)
```
---
## Логирование
Логирование отсутствует.
---
## Ошибки
Компонент не возвращает коды ошибок. Функции `zh_bmp280_init`, `zh_bmp280_read`, `zh_bmp280_write_reg`, `zh_bmp280_read_reg` возвращают `bool` (true при успехе). Остальные функции имеют тип `void` или возвращают однобайтовый статус SPI (`uint8_t`).
| Условие | Поведение |
| --------- | ---------- |
| Нулевое показание АЦП | `zh_get_battery_voltage()` возвращает 0.0 |
| Неверный `CHIP_ID` BMP280 | `zh_bmp280_init()` возвращает false, флаг `bmp280_present = false`, при следующем цикле предпринимается повторная попытка инициализации |
| Таймаут ожидания `TWINT` | `zh_i2c_wait()` возвращает false, операция TWI прерывается |
| Неверный статус TWI (NACK, ошибка шины) | `zh_i2c_start()` / `zh_i2c_write()` возвращают false, вызывающая функция выполняет `zh_i2c_stop()` |
| Таймаут при чтении TWI | `zh_i2c_read_ack()` / `zh_i2c_read_nack()` возвращают `0xFF` |
| Ошибка чтения BMP280 | `zh_bmp280_read()` возвращает false, пакет не формируется, `bmp280_present = false` |
| `var1 == 0` при компенсации давления | `zh_bmp280_compensate_pressure()` возвращает 0.0 |
| Превышение таймаута передачи (~100 мс) | Цикл ожидания IRQ прерывается, передача может быть неполной |
---
## Ограничения
1. **Только передача (TX-only)** — компонент не принимает данные, шлюз не может отправить подтверждение на уровне приложения.
2. **Отсутствие шифрования** — CRC включён, но AES-шифрование не используется. Пакеты могут быть перехвачены.
3. **Жёстко зашитый адрес шлюза** — смена адреса требует перепрошивки.
4. **Таймаут передачи ~100 мс** — если шлюз недоступен, передача прерывается. Аппаратные ретрансмиты nRF24L01+ (`SETUP_RETR = 0xFF`: 15 попыток с интервалом до 500 мс) включены.
5. **Отсутствие валидации `dig_t1`** — в `zh_bmp280_compensate_temperature()` нет проверки `dig_t1 == 0`, что может привести к делению на ноль.
6. **Точность измерения батареи** — зависит от стабильности внутреннего опорного напряжения 1,1 В.
7. **Программные задержки в TWI** — обмен с BMP280 выполняется на аппаратном TWI, но ожидание `TWINT` реализовано поллингом с таймаутом; прерывания TWI не используются.
8. **Задержка между измерениями ~5 минут** — определяется произведением `WDT_WAKE_COUNT` (38) на интервал WDT (~8 секунд). В течение этого времени пакет не передаётся.
9. **Давление в мм рт. ст.** — `zh_bmp280_compensate_pressure()` возвращает давление в Паскалях, для перевода в пакет умножается на `0.00750062` (коэффициент пересчёта Па → мм рт. ст.).
10. **Температура и давление без масштабирования** — значения передаются как целые числа (°C и мм рт. ст.), дробная часть теряется.
---
## Требования для сборки
- PlatformIO с плагином `platform-atmelavr`
- AVR-GCC (входит в состав PlatformIO)
- Библиотека `zh_rf_config` (подключается через `lib_deps` в `platformio.ini`)
- Программатор USBasp (или совместимый)
- Фьюзы: LFUSE=`0xE2`, HFUSE=`0xDF`, EFUSE=`0x07` (8 МГц, без делителя)
---
## Установка
### Сборка и прошивка через PlatformIO
```bash
pio run -e ATmega328P -t upload
```
### Подключение в проекте
Компонент является самодостаточной прошивкой — не подключается как библиотека. Для интеграции в другой проект скопируйте `src/main.c`, добавьте зависимость `zh_rf_config` и адаптируйте макросы конфигурации.
```ini
; platformio.ini
lib_deps =
https://github.com/aZholtikov/zh_rf_config
```
```c
// Зависимости: стандартные заголовки AVR-libc, математика и конфигурация протокола
#include "avr/io.h"
#include "avr/sleep.h"
#include "avr/fuse.h"
#include "avr/interrupt.h"
#include "util/delay.h"
#include "math.h"
#include "zh_rf_config.h"
```