[I2C Tools](https://i2c.wiki.kernel.org/index.php/I2C_Tools) is a simple but very useful tool for developing I2C related applications, which is also famous in Linux platform. This example just implements some of basic features of [I2C Tools](https://i2c.wiki.kernel.org/index.php/I2C_Tools) based on [esp32 console component](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/system/console.html). As follows, this example supports five command-line tools:
1.`i2cconfig`: It will configure the I2C bus with specific GPIO number, port number and frequency.
2.`i2cdetect`: It will scan an I2C bus for devices and output a table with the list of detected devices on the bus.
3.`i2cget`: It will read registers visible through the I2C bus.
4.`i2cset`: It will set registers visible through the I2C bus.
5.`i2cdump`: It will examine registers visible through the I2C bus.
If you have some trouble in developing I2C related applications, or just want to test some functions of one I2C device, you can play with this example first.
To run this example, you should have any ESP32, ESP32-S and ESP32-C based development board. For test purpose, you should have a kind of device with I2C interface as well. Here we will take the CCS811 sensor as an example to show how to test the function of this sensor without writing any code (just use the command-line tools supported by this example). For more information about CCS811, you can consult the [online datasheet](http://ams.com/ccs811).
See the [Getting Started Guide](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.
*`-r` option to specify the register address you want to inspect.
*`-l` option to specify the length of the content.
* Here the returned value 0x10 means that the sensor is just in the boot mode and is ready to go into application mode. For more information about CCS811 you should consult the [official website](http://ams.com/ccs811).
### Change the working mode
```bash
esp32> i2cset -c 0x5b -r 0xF4
I (734717) cmd_i2ctools: Write OK
esp32> i2cset -c 0x5b -r 0x01 0x10
I (1072047) cmd_i2ctools: Write OK
esp32> i2cget -c 0x5b -r 0x00 -l 1
0x98
```
* Here we change the mode from boot to application and set a proper measure mode (by writing 0x10 to register 0x01)
* Now the status value of the sensor is 0x98, which means a valid data is ready to read
### Read the sensor data
```bash
esp32> i2cget -c 0x5b -r 0x02 -l 8
0x01 0xb0 0x00 0x04 0x98 0x00 0x19 0x8f
```
* The register 0x02 will output 8 bytes result, mainly including value of eCO~2~、TVOC and there raw value. So the value of eCO~2~ is 0x01b0 ppm and value of TVOC is 0x04 ppb.
## Troubleshooting
* I don’t find any available address when running `i2cdetect` command.
* Make sure your wiring connection is right.
* Some sensor will have a “wake up” pin, via which user can put the sensor into a sleep mode. So make sure your sensor in **not** in the sleep state.
* Currently the `i2cdump` only support those who have the same content length of registers inside the I2C device. For example, if a device have three register addresses, and the content length at these address are 1 byte, 2 bytes and 4 bytes. In this case you should not expect this command to dump the register correctly.
(For any technical queries, please open an [issue](https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you as soon as possible.)
