2 layers19 × 76 mm
Sub
google/mozc-devices
Circuit diagrams and firmware source code for Gboard DIY keyboards
15 parts3kApache-2.0
2 layers12 × 33 mm
Cheap driverless USB-C to 1.8 V serial console adapter for the TC8 (CH340N + BSS138 level shifters). atopile + KiCad.
- Size
- 12 × 33 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 15
- Nets
- 15
- Pads
- 66
- Tracks, vias
- 145, 21
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 28 Jun 2026
- Updated
- 28 Jun 2026
Overview
Elec is an open-source printed circuit board by Polycom-Open-Firmware, from the Polycom-Open-Firmware/polycom_serial_adapter repository on GitHub. It is a 2-layer board of 12 × 33 mm with 15 parts on 15 nets, routed with 145 tracks and 21 vias.
Its parts include 6 resistors, 6 ICs and 3 capacitors. It belongs with the interfaces and adapters boards of this library.
README
README.mdTC8 1.8 V USB-Serial Adapter
Driverless USB-C → 1.8 V serial console dongle for the TC8 target. atopile source in elec/src/, KiCad project in elec/layout/default/.
USB-C ──► CH340N (USB-UART) ──► 2× BSS138 level shifters ──► GH1.25 (1.8 V target)BOM (~$0.75/board, all LCSC)
| Ref | Part | LCSC | Pkg |
|---|---|---|---|
| U1 | USB-C receptacle TYPE-C-31-M-12 | C165948 | SMD |
| U2 | CH340N USB-UART | C2977777 | SOP-8 |
| U3 | GH1.25 4P SM04B-GHS-TB | C189895 | SMD |
| U4 | USBLC6-2SC6 ESD | C7519 | SOT-23-6 |
| U5,U6 | BSS138 level-shift FET | C52895 | SOT-23 |
| R1,R2 | 5.1 k (CC pulldowns) | C25905 | 0402 |
| R3–R6 | 10 k (shifter pull-ups) | C25744 | 0402 |
| C1 | 4.7 µF (VBUS bulk) | C19666 | 0603 |
| C2,C3 | 100 nF (CH340N decoupling) | C1525 | 0402 |
Order-ready file: LCSC_BOM.csv.
GH1.25 pinout
| Pin | Signal |
|---|---|
| 1 | VCC 1.8 V (level-shifter reference) |
| 2 | device TXD |
| 3 | GND |
| 4 | device RXD |
CH340N runs on USB 5 V; each line is one BSS138 cell (gate referenced to GH pin 1's 1.8 V). Target never sees >1.8 V.
Parts
15| Qty | Value | Footprint | References |
|---|---|---|---|
| 6 | lib:R0402 | R1, R2, R3, R4, R5, R6 | |
| 2 | lib:C0402 | C2, C3 | |
| 2 | ? | lib:SOT-23-3_L2.9-W1.6-P1.90-LS2.8-BR | U5, U6 |
| 1 | lib:C0603 | C1 | |
| 1 | ? | lib:SOT-23-6_L2.9-W1.6-P0.95-LS2.8-BL | U4 |
| 1 | ? | lib:USB-C_SMD-TYPE-C-31-M-12_1 | U1 |
| 1 | ? | lib:SOP-8_L4.9-W3.9-P1.27-LS6.0-BL | U2 |
| 1 | ? | lib:CONN-SMD_4P-P1.25_SM04B-GHS-TB-LF-SN | U3 |
Questions
How big is the Elec PCB?
It measures 12 × 33 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Elec use?
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.
Where can I download the Elec KiCad files?
From the Polycom-Open-Firmware/polycom_serial_adapter repository on GitHub, at the commit this page was made from: the board is elec/layout/default/default.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the Elec design in my own project?
Its repository states no licence, so its author keeps all rights: ask Polycom-Open-Firmware before reusing the design.
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