BME280 Sensor Library
SDA - GPIO18; SCL - GPIO19
CSB em VCC
Address 0x77 com SD0 em VCC; 0x76 com SD0 em GND
SPI max 10MHz, I2C max 3.4MHz
Modes:
- sleep
- forced
- normal
faster to read pressure even if there was no measurement
0xF7 to 0xFE (temp, press, hum) temp e press 20bit unsigned hum 16bit unsigned
Using calibration parameters (trimming values) Especific from the device, set in production (can't be changed) 0x88 to 0xA1, and 0xE1 to 0xF0
Given formulas in page 25
register address 0xD0 expected answer 0x60
0xF5, 0xF4
github /BoschSensortec/BME280_driver
(kolban's book page 271 - Using I2C)
The ESP-IDF provides an I2C driver that allows us to control I2C functions from a C program at a high level without having to resort to low level register manipulation.
Before we can use an I2C port, we need to configure it.Arbitrary exposed pins can be used for I2C.
To use I2C, we must configure the I2C environment
i2c_param_config()
- port
- structure with details on the configuration
- mode: I2C_MODE_MASTER or I2C_MODE_SLAVE
- sda_io_num, scl_io_num (any two arbitrary pins)
- sda_pullup_en, scl_pullup_en
- clk_speed
i2c_driver_install()
- port
- buffer sizes if in slave mode
To send a command, we build the structure of that command then ask for it to be transmitted.
i2c_cmd_link_create()
- command handle
i2c_master_start(cmd)
- declare that the command (cmd) starts with an I2C request
i2c_master_write_byte()/i2c_master_write()
- associate the data we want to send
- Read/Write operation: constants I2C_MASTER_READ and I2C_MASTER_WRITE
- (ADDRESS << 1) | I2C_MASTER_READ
- (ADDRESS << 1) | I2C_MASTER_WRITE
i2c_master_stop(cmd)
- indicate the command population is completed
i2c_master_cmd_begin()
- all commands buffered are transmitted
release the command handle and create a new one for the next transmission