USB I2C Click

How does it work?

USB I2C Click is based on the MCP2221A, a USB 2.0 to I2C/UART protocol converter with GPIO from Microchip. The heart of the MCP2221A is the Bus Matrix module that controls and manages all data transfers between the USB, the UART, and the I2C. It also takes care of the command requests generated by the USB host controller and commands for controlling the UART, GPIO, ADC, DAC, and clock output functions. The 448-byte buffer can handle data throughput at any supported UART baud rate with 64-byte TX and 384-byte RX. The Human Interface Device standard can count on a 64-byte buffer to handle data throughput at any I2C baud rate.

The USB HID and CDC modules in the MCP2221A are full-speed USB 2.0 compliant, with fully configurable VID and PID assignments and stored on-chip descriptors. The USB Transceiver obtains power internally connected to the 3.3V regulator, the AP7331, of the USB I2C Click board. The MCP2221A can be bus-powered or self-powered; it can be powered through the mikroBUS™ socket or over the mini-USB connector.

The USB I2C Click can use UART or I2C interface to communicate to the host MCU over the mikroBUS™ socket. These two interfaces exist concurrently and can be selected independently according to the application. The I2C interface acts as an I2C Master, and the data to Write/Read on the I2C bus is conveyed by the USB interface that can read/write blocks of up to 65.535 bytes long, with up to 400KHz clock rate.

This Click board™ features two 4-pin headers on the board’s edges with additional GPIOs (GP0-GP3) and I2C pins plus VCC and GND. Those GPIO pins can be used as general-purpose I/O or alternate functions such as ADC, DAC, and IOC (external interrupt edge detector). The board also features UART DAT RX, TX LEDs, and I2C DAT status LEDs. To use these LEDs, you must select IND on the GP SEL jumper (the HDR is selected by default). If so, the GP0, GP1, and GP3 can not be used as GPIO on the HD1 header.

This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used as a reference for further development.

Specifications

Pinout diagram

This table shows how the pinout on USB I2C Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
	NC	2	RST	INT	15	NC
	NC	3	CS	RX	14	TX	UART TX
	NC	4	SCK	TX	13	RX	UART RX
	NC	5	MISO	SCL	12	SCL	I2C Clock
	NC	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

USB I2C Click electrical specifications