USB keyboard on CH9350L host module
USB host module with the WCH CH9350L, plugged onto a 4-pin header (VCC, GND, TXD, RXD); its USB-A socket (VBUS, D+, D−) takes a USB keyboard. Key reports of the keyboard leave on TXD as UART frames (115200 8N1, state 0: 57 AB 88 0B 11 MOD 00 K0…K5 CTR CHK), status 57 AB 82 A3 about once a second. VCC 5 V goes on to VBUS; TXD/RXD are 3.3 V logic (module regulator). A device is detected by its pull-up on D− / D+ (15 kΩ pull-downs on the host side).
Key data
- Category
- Interfaces
- Simulation model
- Behavioural mixed-signal model
- Manufacturer part number
- CH9350L
- Reference prefix
- U
- Pins
- 8
- Land pattern
- PinHeader_1x04_P2.54mm_Vertical
Notes
The module turns a USB keyboard into UART frames. In the simulation the keyboard is a "USB keyboard (your keyboard)" part on the USB side: while the simulation runs, the keys you press on your computer reach the module and leave on TXD.
- Connect VBUS, D+, D− and GND of the USB socket to a "USB keyboard" part.
- Read TXD with a UART receiver at 115200 baud, 8N1 (for example the RX pin of a microcontroller).
- TXD and RXD are 3.3 V logic; VCC needs 5 V because it is passed on to VBUS.
Simulation model
A behavioural model implements the interface of the chip (registers, protocol, timing) at its pins. The pins are connected to the analog circuit like CMOS pins.
- Model
- ch9350l
- Supply pins
- VCC / GND
Pins 8
| Pin | Name | Use |
|---|---|---|
| VCC | VCCSupply pin | Module supply 5 V (passed on to the USB socket) |
| GND | GNDGround pin | Ground |
| TXD | TXDOutput pin | UART out (3.3 V): key reports to the RX of the microcontroller |
| RXD | RXDInput pin | UART in (3.3 V): commands from the microcontroller |
| VBUS | USB VBUSSupply pin | USB socket: 5 V to the keyboard |
| DP | USB D+Passive pin | USB socket D+ |
| DM | USB D−Passive pin | USB socket D− |
| UGND | USB GNDGround pin | USB socket ground |
PCB
PinHeader_1x04_P2.54mm_VerticalCH9350L USB host module with USB-A socket on a 4-pin header (1 VCC 5 V, 2 GND, 3 TXD, 4 RXD)