2 layers124 × 112 mm
2 layers21 × 39.4 mm
Rpi uart
avahidi/rpi-uartThis UART board for the Raspberry Pi, is one of those Sunday morning projects that turned out to be quite useful. It lets you to power and talk to the board using only a micro-USB cable. Hence you can go from this mess
- Size
- 21 × 39.4 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 28
- Nets
- 14
- Pads
- 81
- Tracks, vias
- 144, 4
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 4
- Created
- 19 Mar 2023
- Updated
- 19 Mar 2023
Overview
Rpi uart is an open-source printed circuit board by avahidi, from the avahidi/rpi-uart repository on GitHub. It is a 2-layer board of 21 × 39.4 mm with 28 parts on 14 nets, routed with 144 tracks and 4 vias.
It is built around the CH340G and TLV1117-33DCY. Its parts include 7 ICs, 7 connectors, 5 capacitors, 4 diodes and 3 resistors. It belongs with the interfaces and adapters boards of this library.
Main components
2README
README.rstrpi-uart
This UART board for the Raspberry Pi, is one of those Sunday morning projects that turned out to be quite useful. It lets you to power and talk to the board using only a micro-USB cable. Hence you can go from this mess
.. image:: doc/before.jpg :alt: connecting to the rpi using a serial to USB cable
. . . to this:
.. image:: doc/after.jpg :alt: connecting to the rpi using this board
To me the main advantage of this is that I can quickly move it between different boards.
Open hardware
The PCB was developed using KiCad and is published under the CERN Open Hardware License v1.2.
.. image:: doc/pcb.jpg
Some footprints have been modified to eliminate oval plated holes which may be expensive to manufacture. I have also tried to make the design easy to solder, although you may still find the fine-pitch USB connector a bit challenging. The CH340g IC was chosen to avoid depending on FTDI or counterfeit FTDI chips.
Operations modes
The board can be populated in a couple of ways to allow different powering modes. Only one of which will not fry your Raspberry Pi so pay attention to this!
.. image:: doc/schematics.png
RPi mode
To connect directly to a Raspberry Pi you should populate the following components::
component | type | notes
========================================================
J2 | micro USB connector |
U1 | CH340g |
Y1 | 12MHz crystal |
C1,C2 | 22pF 0805 SMD caps | probably optional
R2 | 10K 0805 SMD resistor | optional
D1 | 0805 LED | optional
J5 | solder bridge | bridge
J4 | solder bridge | MUST BE OPEN
If you want to power it from the same cable, you will also need these::
component | type | notes
========================================================
C4 | 22u SMD cap |
SW1 | Switch | or bridge 1-2 for permanent power
Full 5.0v modeIf you are using this as a stand-alone USB-to-serial converter and WITHOUT a raspberry pi and want to have 5.0v transmit and receive signals you will need to bridge the 5.0 and 3.3 rails::
component | type | notes
========================================================
J5 | solder bridge | MUST BE OPEN
J4 | solder bridge | bridgeLocal 3.3v mode
If you instead want to use a locally generated 3.3v::
component | type | notes
========================================================
J5 | solder bridge | MUST BE OPEN
J4 | solder bridge | MUST BE OPEN
U2 | 3.3v SMD regulator |
C3, C5 | 100n 0805 SMD caps |
Remaining componentsThe following components are not needed and should not be populated::
component | type | notes
========================================================
D4 | protection SMD didoe | protection for cheap regulators
R3, R4 | 10K 0805 SMD resistors | for RX/TX LED
D2, D3 | 0805 SMD LEDs | RX/TX LEDParts
28| Qty | Value | Footprint | References |
|---|---|---|---|
| 5 | Via | footprints:via | U3, U4, U5, U6, U7 |
| 3 | 10K | Resistors_SMD:R_0805_HandSoldering | R2, R3, R4 |
| 3 | LED | LEDs:LED_0805_HandSoldering | D1, D2, D3 |
| 2 | 100n | Capacitors_SMD:C_0805_HandSoldering | C3, C5 |
| 2 | 22p | Capacitors_SMD:C_0805_HandSoldering | C1, C2 |
| 2 | Conn_01x05 | footprints:pads_01x05 | J1, J3 |
| 2 | GS2 | Connectors:GS2 | J4, J5 |
| 1 | 12MHz | Crystals:Crystal_C26-LF_d2.1mm_l6.5mm_Vertical | Y1 |
| 1 | 22u | Capacitors_SMD:CP_Elec_8x10 | C4 |
| 1 | 3.3v | Measurement_Points:Measurement_Point_Round-SMD-Pad_Small | J7 |
| 1 | 5v | Measurement_Points:Measurement_Point_Round-SMD-Pad_Small | J6 |
| 1 | CH340g | Housings_SOIC:SOIC-16W_5.3x10.2mm_Pitch1.27mm | U1 |
| 1 | D | Diodes_SMD:D_SMB | D4 |
| 1 | SW_Push_SPDT | Buttons_Switches_THT:SW_CuK_OS102011MA1QN1_SPDT_Angled | SW1 |
| 1 | TLV1117-33 | TO_SOT_Packages_SMD:SOT-223 | U2 |
| 1 | USB_OTG | Connectors:USB_Micro-B | J2 |
Questions
How big is the Rpi uart PCB?
It measures 21 × 39.4 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Rpi uart use?
28 parts, built around the CH340G and TLV1117-33DCY. 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 Rpi uart KiCad files?
From the avahidi/rpi-uart repository on GitHub, at the commit this page was made from: the board is pcb/rpi-uart.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the Rpi uart design in my own project?
Its repository states no licence, so its author keeps all rights: ask avahidi before reusing the design.
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