This is a generic embedded driver for the Sensirion SGP41 sensor. It enables developers to communicate with the SGP41 sensor on different hardware platforms by only adapting the I2C communication related source files.
So we need to adjust two files according to your platform.
This file contains the implementation of the sensor communication, which
depends on your hardware platform. We provide function stubs for your
hardware's own implementation.
Sample implementations are available for some platforms:
sample-implementations. For Linux based platforms
like Raspberry Pi you can just replace the unimplemented HAL template with the
implementation in sample-implementations/linux_user_space/:
cp sample-implementations/linux_user_space/sensirion_i2c_hal.c ./
Skip this part for Linux based platforms since everything is already setup for this case.
Otherwise you need to check if the libraries <stdint.h> and <stdlib.h> are
provided by your toolchain, compiler or system. If you have no idea on how to
do that you can skip this step for now and come back when you get errors
related to these names when compiling the driver.
The features we use from those libraries are type definitions for integer sizes
from <stdint.h> and NULL from <stdlib.h>. If they are not available you
need to specify the following integer types yourself:
int64_t= signed 64bit integeruint64_t= unsigned 64bit integerint32_t= signed 32bit integeruint32_t= unsigned 32bit integerint16_t= signed 16bit integeruint16_t= unsigned 16bit integerint8_t= signed 8bit integeruint8_t= unsigned 8bit integer
In addition to that you will need to specify NULL. For both we have a
detailed template where you just need to fill in your system specific values.
Now we are ready to compile and run the example usage for your sensor.
Pass the source .c and header .h files in this folder into your C compiler
and run the resulting binary. This step may vary, depending on your platform.
Here we demonstrate the procedure for Linux based platforms:
- Open up a terminal.
- Navigate to the directory where this README is located.
- Run
make(this compiles the example code into one executable binary). - Run the compiled executable with
./sgp41_i2c_example_usage - Now you should see the first measurement values appear in your terminal. As a next step you can adjust the example usage file or write your own main function to use the sensor.
In these files you can find the implementation of the I2C protocol used by Sensirion sensors. The functions in these files are used by the embedded driver to build the correct frame out of data to be sent to the sensor or receive a frame of data from the sensor and convert it back to data readable by your machine. The functions in here calculate and check CRCs, reorder bytes for different byte orders and build the correct formatted frame for your sensor.
These files contain the implementation of the hardware abstraction layer used
by Sensirion's I2C embedded drivers. This part of the code is specific to the
underlying hardware platform. This is an unimplemented template for the user to
implement. In the sample-implementations/ folder we provide implementations
for the most common platforms.
In this file we keep all the included libraries for our drivers and global
defines. Next to sensirion_i2c_hal.c it's the only file you should need to
edit to get your driver working.
In these files you can find some helper functions used by Sensirion's embedded drivers. It mostly contains byte order conversions for different variable types. These functions are also used by the UART embedded drivers therefore they are kept in their own file.
After each restart of the sensor or when the hotplates have been switched off, the conditioning command must be called from idle mode. The conditioning heats the hotplate of the NOx pixel to a different temperature compared to the measurement mode enabling a faster switch-on thereafter.
It is recommended to execute the conditioning for 10s, but 10s must not be exceeded to avoid damage to the sensing material.