Inter-Integrated Circuit (I2C)

[中文]

Does ESP8266 support I2C slave mode?

Not supported. If you want to use this feature, we recommend using the ESP32 or ESP32-S2 chip. ESP32 example: i2C_self_test.

Is ESP8266 I2C realized via software programming?

Yes, ESP8266 I2C is realized via GPIO software programming.

Is it normal for some spikes to frequently appear on the data line when the ESP32 chip I2C is working (especially in fast mode), often after the falling edge of the 8th/9th clock?

The spike on the data line at the 8th/9th clocks is caused by the I2C master-slave control handover. It is a normal phenomenon and is mentioned in the I2C protocol.

How can the ESP32 chip, as an I2C master, wait for the slave to process the data before receiving it? For example, when reading data through i2c_master_read_to_device, the slave needs to return data immediately after accepting the command, but in reality, some slave devices need to wait for a while after receiving the command before they can return data.

This can be realized by dividing i2c_master_read_device into the following three steps:

  1. Input commands and address: i2c_cmd_link_create_static > i2c_master_start > i2c_master_write_byte > i2c_master_cmd_begin > i2c_cmd_link_delete_static

  2. Delay

  3. Read data of the slave: i2c_cmd_link_create_static > i2c_master_read > i2c_master_stop > i2c_master_cmd_begin > i2c_cmd_link_delete_static

When using the ESP32 chip, can GPIO32 and GPIO33 be configured as I2C_SDA and I2C_SCL respectively?

Yes. I2C pins of the ESP32 chip can be remapped by any available GPIOs. Please refer to “4.2 Peripheral Pin Configurations” of ESP32 Datasheet. If you do not need an external 32.768 KHz crystal, you can use GPIO32 and GPIO33 as I2C pins.


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