Power

• USB C Port - at the top edge of the board is the USB C port. Use this port to connect the breakout to your computer, laptop or even a phone or tablet. This port provides power and ground to the CH9328, as well as an HID connection to your chosen device.
• VCC - this is the power output from the USB C port. It is 5V by default.
• GND - common ground for power and logic.

UART

• RX - This is the UART RX receive input for the CH9328. Connect this pin to the UART TX transmit output pin on your microcontroller.

Reset

• RST - This is the reset line for the CH9328. If you want to perform a hard reset, set this pin low.

JST SH Port

• JST SH - 1mm pitch JST port for use with 3-pin JST SH cables. It has connections for:
  • GND - common ground for power and data. It is the black wire on the JST SH cable.
  • VCC - power output from the USB C port. It is the red wire on the JST SH cable.
  • RX - RX input for the CH9328. It is the white wire on the JST SH cable.

Switches

There are four switches on the breakout board labeled 1, 2, 3 and 4. Switch 1 is used to configure the "Upload speed" - when the switch is on, it is set to normal speed and when it is off it is set to high speed (approximately 2x the speed of normal speed). For most cases it doesn't matter which way its set.

Switches 2, 3 and 4 configure the 'Mode' for the CH9328. You'll need to select your 'Mode' before powering up the board. There are four modes available:

• Mode 0:
  Visible ASCII characters are sent as-is: if you send ASCII "A", an "A" is typed. If 0x1B is received, it is converted to the Enter key
• Mode 1:
  Visible ASCII characters are sent as-is: if you send ASCII "A", an "A" is typed
• Mode 2:
  Visible ASCII characters are sent as-is: if you send ASCII "A", an "A" is typed. If 0x28 is received, it is converted to the Enter key
• Mode 3:
  This is the mode for sending raw 8-byte HID reports. This is also good if you want more control over the keypresses, or keyholds, or to mimic a non-US keyboard because you can control exactly what control codes are sent and when.

The modes are selected with these switch combinations:

VCC Jumper

On the back of the board is the VCC jumper. It is outlined in white on the board silk and is labeled VCC. If you cut the 5V pad from the center pad, this will disconnect the 5V line output from the VCC pin. If you solder the 3V pad to the center pad, it will connect the 3V output to the VCC pin. This will cause the output voltage from VCC to be 3V.

Status LEDs

There are two LEDs on the front of the board:

• HID - This is the HID USB status LED. It is a yellow LED and it is connected to the ACT pin on the CH9328. When the USB configuration setup is complete, this LED will light up.
• USB - This is the serial UART status LED. It is a red LED and it is connected to the T_LED pin on the CH9328. This LED is lit when a serial UART message is received on the RX pin and is sent via USB. If there is no UART activity, then this LED will be off.