I2C busses on the Tanmatsu mainboard

Internal bus

The internal I2C bus facillitates communication between the ESP32-P4 application processor and the on-board peripherals of Tanmatsu.

Device	Role	Address	Description
ESP32-P4	Controller	-	Runs user application
ESP32-C6 radio	-	-	I2C bus connection is not currently being used
CH32V203 coprocessor	Peripheral	0x5F	Controls power management, keyboard and RTC
ES8156 audio codec	Peripheral	0x08	Audio codec for the stereo audio output
BMI270 orientation sensor	Peripheral	0x68	Accelerometer and gyroscope orientation sensor
Internal Add-On EEPROM	Peripheral	0x50	Optional: a small EEPROM chip used to identify the attached add-on board
SCD4x CO2 sensor	Peripheral	0x62	Optional: a carbon dioxide sensor attached to the sensor header

The internal add-on EEPROM resides on the add-on board and is thus only available when an add-on is attached.

The SCD4x CO2 sensor is an optional module which can be attached to the sensor header which can be soldered in by the user.

Power management bus

The power management I2C bus allows the CH32V203 coprocessor to configure the BQ25895.

Device	Role	Address	Description
CH32V203 coprocessor	Controller	-
BQ25895 PMIC	Peripheral	0x6A	Power management

QWIIC bus

The QWIIC connector on the Tanmatsu mainboad is connected to GPIO 33 (SDA) and GPIO 32 (SCL), allowing the user to choose between I2C (both controller and peripheral) and I3C controller modes. There are no other devices attached to these pins, allowing the pins to be used for any purpose.

CATT bus

The CATT connector on the Tanmatsu mainboard is connected to eight dedicated GPIO pins. Users can reconfigure each of these GPIO pins. On startup pins GPIO 12 (SDA) and GPIO 13 (SCL) are used as I2C bus. If an EEPROM is detected at I2C address 0x50 it will be read to identify the connected add-on board.