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https://github.com/sensirion/embedded-uart-sen44

Embedded driver for the SEN44 sensor module.
https://github.com/sensirion/embedded-uart-sen44

driver embedded sen44 sensirion sensirion-embedded-drivers sensirion-sensors uart

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Embedded driver for the SEN44 sensor module.

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README 

        
# Sensirion Embedded UART SEN44 Driver



This is a generic embedded driver for the Sensirion SEN44 sensor module. It enables

developers to communicate with the SEN44 sensor module on different hardware platforms

by only adapting the UART communication related source files.






# Getting started



## Connecting the Sensor



Your sensor has the four different connectors: VCC, GND, SDA, SCL, SEL (the sixth connector will not be used for now).






| *Pin* | *Name* | *Description* | *Comments* |

|-------|--------|---------------|------------|

| 1     | VDD    | Supply Voltage | 5V ±10%

| 2     | GND    | Ground |

| 3     | RX     | UART: Receiving pin for communication | TTL 5V and LVTTL 3.3V compatible

|       | SDA    | I2C: Serial data input / output | TTL 5V and LVTTL 3.3V compatible

| 4     | TX     | UART: Transmission pin for communication | TTL 5V and LVTTL 3.3V compatible

|       | SCL    | I2C: Serial clock input | TTL 5V and LVTTL 3.3V compatible

| 5     | SEL    | Interface select | Leave floating or pull to VDD to select UART

|       |        |  | Pull to GND to select I2C

| 6     | NC     | Do not connect |



## Implement the UART Interface



So we need to adjust two files according to your platform.



### Edit `sensirion_uart_hal.c`



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`](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_uart_hal.c ./

```



### Edit `sensirion_config.h`



Skip this part for Linux based platforms since everything is already setup for

this case.



Otherwise you need to check if the libraries `` and `` 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 `` and `NULL` from ``. If they are not available you

need to specify the following integer types yourself:



* `int64_t` = signed 64bit integer

* `uint64_t` = unsigned 64bit integer

* `int32_t` = signed 32bit integer

* `uint32_t` = unsigned 32bit integer

* `int16_t` = signed 16bit integer

* `uint16_t` = unsigned 16bit integer

* `int8_t` = signed 8bit integer

* `uint8_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.



## Compile and Run



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:



1. Open up a terminal.

2. Navigate to the directory where this README is located.

3. Run `make` (this compiles the example code into one executable binary).

4. Run the compiled executable with `./sen44_uart_example_usage`

5. 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.



# Background



## Files



### sensirion\_shdlc.[ch]



In these files you can find the implementation of the SHDLC 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 the checksum, reorder bytes

for different byte orders and build the correct formatted frame for your

sensor.



### sensirion\_uart\_hal.[ch]



These files contain the implementation of the hardware abstraction layer used

by Sensirion's UART 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.



### sensirion\_config.h



In this file we keep all the included libraries for our drivers and global

defines. Next to `sensirion_uart_hal.c` *it's the only file you should need to

edit to get your driver working.*



### sensirion\_common.[ch]



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 I2C embedded drivers therefore they

are kept in their own file.