This library provides a platform independent driver for the CCS811 Air Quality measurement chip.
The details of the I2C bus communication are left to the implementation. In ccs811.h, a struct describing the IAQ device is defined as follows:
struct ccs811_dev_s {
/*! Device address; default is 0x5B */
uint8_t address;
/*! Harware ID */
uint8_t hw_id;
/*! Harware version */
uint8_t hw_version;
/*! Firmware version of the boot code */
uint16_t fw_boot_version;
/*! Firmware version of the application code */
uint16_t fw_app_version;
/*! Read function pointer for the I2C implementation */
ccs811_func_ptr read;
/*! Write function pointer for the I2C implementation */
ccs811_func_ptr write;
};
Read and write operations are defined as as function pointers with type of ccs811_func_ptr which looks like:
typedef uint8_t (*ccs811_func_ptr)(ccs811_dev_t *dev, uint8_t reg_addr,
uint8_t *data, uint16_t len);
These should be implemented in the code that calls this. An example of implementation in the STM32 domain using the HAL provided by the manufacturer might looks like this
uint8_t read_iaq_i2c(ccs811_dev_t *dev, uint8_t reg_addr, uint8_t *data,
uint16_t len) {
uint8_t result = 0;
result = HAL_I2C_Master_Transmit(&hi2c1, dev->address, ®_addr, 1, 100);
if (result == HAL_OK) {
result = HAL_I2C_Master_Receive(&hi2c1, dev->address, data, len, 100);
}
return hi2c1.ErrorCode;
}
for the read function where dev is defined as something that looks like
ccs811_dev_t iaq_dev = {
.address = (CCS811_DEFAULT_ADDRESS << 1),
.read = &read_iaq_i2c,
.write = &write_iaq_i2c
};
(in the ST HAL, the address is a 7 bit address taht must be left-shifted by 1 bit). The write implementation is left as an exercise for the user.