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google/mozc-devices
Circuit diagrams and firmware source code for Gboard DIY keyboards

A simple USB to UART board designed with KiCad.
HT42B534USB2UART is an open-source printed circuit board by jiegec, from the jiegec/HT42B534USB2UART repository on GitHub. It is a 2-layer board of 29.2 × 20.3 mm with 15 parts on 11 nets, routed with 48 tracks and 6 vias.
Its parts include 7 capacitors, 3 resistors, 3 connectors, 1 IC and 1 diode. It belongs with the interfaces and adapters boards of this library.
A simple USB to UART board. Designed with KiCad. Manufactured and tested.

The voltage of RX/TX should match VIO.
Reference, Value, Footprint, Datasheet, Product
"U1","HT42B534_8SOP","Package_SO:SOP-8_3.9x4.9mm_P1.27mm","https://www.holtek.com/documents/10179/116711/HT42B534-xv110.pdf","https://item.szlcsc.com/504007.html"
"C1","0.1uF","Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder","~"
"J1","USB_A","Connector_USB:USB_A_CNCTech_1001-011-01101_Horizontal","~","https://item.szlcsc.com/98530.html"
"R2","33","Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder","~"
"R1","33","Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder","~"
"C6","47pF","Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder","~"
"C7","47pF","Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder","~"
"C3","1uF","Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder","~"
"C2","0.1uF","Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder","~"
"C4","10uF","Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder","~"
"C5","0.1uF","Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder","~"
"R3","330","Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder","~"
"D1","LED","Diode_SMD:D_0603_1608Metric_Pad1.05x0.95mm_HandSolder","~"
"J3","Conn_01x03","Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical","~"
"J2","Conn_01x04","Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Horizontal","~"lsusb output:
$ lsusb
Bus 000 Device 001: ID 04d9:b534 Holtek Semiconductor, Inc. USB TO UART BRIDGE Serial: 0000System Information:
USB TO UART BRIDGE:
Product ID: 0xb534
Vendor ID: 0x04d9 (Holtek Semiconductor, Inc.)
Version: 2.10
Serial Number: 0000
Speed: Up to 12 Mb/s
Manufacturer: HOLTEK
Location ID: 0x00142000 / 12
Current Available (mA): 500
Current Required (mA): 100
Extra Operating Current (mA): 0Copyright 2020-2021 Jiajie Chen
SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file except in compliance with the License, or, at your option, the Apache License version 2.0. You may obtain a copy of the License at
https://solderpad.org/licenses/SHL-2.1/
Unless required by applicable law or agreed to in writing, any work distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
| Qty | Value | Footprint | References |
|---|---|---|---|
| 3 | 0.1uF | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C1, C2, C5 |
| 2 | 33 | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R1, R2 |
| 2 | 47pF | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C6, C7 |
| 1 | 10uF | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C4 |
| 1 | 1uF | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C3 |
| 1 | 330 | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R3 |
| 1 | Conn_01x03 | Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical | J3 |
| 1 | Conn_01x04 | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Horizontal | J2 |
| 1 | HT42B534_8SOP | Package_SO:SOP-8_3.9x4.9mm_P1.27mm | U1 |
| 1 | LED | Diode_SMD:D_0603_1608Metric_Pad1.05x0.95mm_HandSolder | D1 |
| 1 | USB_A | Connector_USB:USB_A_CNCTech_1001-011-01101_Horizontal | J1 |

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It measures 29.2 × 20.3 mm and has 2 copper layers, 1.6 mm thick.
15 parts. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
From the jiegec/HT42B534USB2UART repository on GitHub, at the commit this page was made from: the board is HT42B534USB2UART.kicad_pcb and its schematic HT42B534USB2UART.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Its repository states no licence, so its author keeps all rights: ask jiegec before reusing the design.