If you have a new I2C application to go (for example, read the temperature data from external sensor with I2C interface), try this as a basic template, then add your own code.
To run this example, you should have one ESP development board (e.g. ESP32-WROVER Kit) or ESP core board (e.g. ESP32-DevKitC). Optionally, you can also connect an external sensor. Here we choose the BH1750 just as an example. BH1750 is a digital ambient light sensor. For more information about it, you can read the [datasheet](http://rohmfs.rohm.com/en/products/databook/datasheet/ic/sensor/light/bh1721fvc-e.pdf) of this sensor.
**Note:** It is recommended to add external pull-up resistors for SDA/SCL pins to make the communication more stable, though the driver will enable internal pull-up resistors.
- GPIO4 is assigned as the data signal of I2C slave port
- GPIO5 is assigned as the clock signal of I2C slave port
- master:
- GPIO1 is assigned as the data signal of I2C master port
- GPIO2 is assigned as the clock signal of I2C master port
- Connection:
- connect GPIO1 with GPIO4
- connect GPIO2 with GPIO5
- connect SDA/SCL of BH1750 sensor with GPIO18/GPIO19
**Note:** It is recommended to add external pull-up resistors for SDA/SCL pins to make the communication more stable, though the driver will enable internal pull-up resistors.
**Note:** There is only one i2c device on ESP32-C3/ESP32-C2, so it is not possible to perform any ESP32/ESP32-S2 self-test example from this repo. However it is possible to test I2C with external devices. If you find anything wrong with your device, please try connecting external pull-up resistors.
- In the `I2C Master` submenu, you can set the pin number of SDA/SCL according to your board. Also you can modify the I2C port number and freauency of the master.
- In the `I2C Slave` submenu, you can set the pin number of SDA/SCL according to your board. Also you can modify the I2C port number and address of the slave.
- In the `BH1750 Sensor` submenu, you can choose the slave address of BH1750 accroding to the pin level of ADDR pin (if the pin level of ADDR is low then the address is `0x23`, otherwise it is `0x5c`). Here you can also control the operation mode of BH1750, each mode has a different resolution and measurement time. For example, in the `One Time L-Resolution` mode, the resolution is 4 Lux and measurement time is typically 16ms (higher resolution means longer measurement time). For more information, you can consult the datasheet of BH1750.
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.
- BH1750 has two I2C address, which is decided by the voltage level of `ADDR` pin at start up. Make sure to check your schemetic before run this example.
(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.)
