USB bridge via LPC11U14 chip for next revision of FABI and FLipMouse (or other devices)
| Pin | I/O | Function |
|---|---|---|
| PIO0_18 | I | RXD of UART |
| PIO0_19 | O | TXD of UART |
| PIO0_17 | I | RXD for HID |
| PIO0_16 | O | power control for external HW (USB deep sleep) |
The LPC chip is wired via UART ( 230400, 8N1 ) to an external MCU (in case of FABI/FLipMouse an ESP32 in the next revision). This LPC acts as a composite USB device with following features:
- HID mouse
- HID keyboard
- HID joystick
- CDC virtual serial port
The HID functions are controlled via pulse width modulated commands, received on pin IO0_17:
- LSB is sent first
- 0 pulse width: 10us
- 1 pulse width: 20us
- stop bit width: 40us
- Maximum length of one packet is 16 Bytes.
If you want to send data via the USB-serial bridge, it is sent via the UART 0 interface.
To fulfill USB specifications, a device needs to support the USB sleep command with very little power consumption. On our boards, this is done via a N-channel MOSFET which switches off the remaining HW (which is not necessary in sleep mode). This MOSFET can be connected to PIO0_16. Output is low in sleep mode, output is high if in active mode.
| Command | Parameter Length | Description |
|---|---|---|
| 'K' | 7bytes | send keyboard report, 1. parameter byte is the modifier byte, all others are max. 6 keycodes |
| 'X' | 7bytes | same as 'K', but an empty report is sent immediately afterwards (releases all keys) |
| 'M' | 4bytes | send mouse report, 1. parameter byte are mouse buttons, 2. is X, 3. is Y and 4th is mouse wheel |
| 'Y' | 4bytes | same as 'M', but an empty report (with cleared mouse buttons) is immediately sent afterwards |
| 'J' | 12bytes | too long to be documented here, please have a look at parser.c:17 for format. |
| 'T' | -- | Send test data via USB, one key is pressed, the mouse is moved and some buttons on the joystick are pressed. |
| 'C' | 1byte | Change bCountryCode for HID, see USB-HID specification. An USB reset will be performed afterwards. |