2 layers64 × 56 mm
Pi adapter
hzeller/spixels
Spixels - 16-SPI LED Raspberry Pi adapter with library (SPI - Pixels).
37 parts41LGPL-3.0
4 layers70 × 56 mm
Pi adapter hc
hzeller/spixels41Spixels - 16-SPI LED Raspberry Pi adapter with library (SPI - Pixels).
- Size
- 70 × 56 mm
- Copper layers
- 4
- Thickness
- 1.6 mm
- Parts
- 40
- Nets
- 68
- Pads
- 220
- Tracks, vias
- 584, 107
- Pours
- 12
- Routed
- Yes
- KiCad
- KiCad 9.0 (file 20241229)
- Created
- 27 May 2016
- Updated
- 28 Feb 2026
Overview
Pi adapter hc is an open-source printed circuit board by hzeller, from the hzeller/spixels repository on GitHub, published under the LGPL-3.0 licence. It is a 4-layer board of 70 × 56 mm with 40 parts on 68 nets, routed with 584 tracks and 107 vias.
It is built around the 74AHCT245D and CL31A226MQHNNNE. Its parts include 30 connectors, 5 capacitors and 4 ICs. It belongs with the interfaces and adapters boards of this library.
Main components
2
74AHCT245D
SOIC-20-300mil-40℃~+125℃ 1 11ns@5.5V,50pF 4.5V~5.5V 74AHCT 8 80uA 8mA 8mA Bidirectional TTL-compatible CMOS Tri-State SOIC-20-300mil Buffers, Drivers, Receivers, Transceivers ROHSNexperiaBuffers, Drivers, Receivers, Transceivers
CL31A226MQHNNNE
120622uF 6.3V X5R ±20% 1206 Multilayer Ceramic Capacitors MLCC - SMD/SMT ROHSSamsung Electro-MechanicsMultilayer Ceramic Capacitors MLCC - SMD/SMT
README
hardware/pi-adapter-16/README.md16 LED strip Raspberry Pi Adapter
Adapter to connect up to 16 SPI-type LED strips (e.g. WS2801, LPD6803 or APA102).
The software to control these SPI outputs can be found in the MultiSPI class
in this project.
The output pins contain GND, CLK and Data. Also, 5V is given which can power shorter LED strips or is useful for active termination of longer wires.
Pinout of each of the connectors:
| GND | CLK | DATA | +5V |
|---|
(GND is pointing towards the Rasbperry Pi GPIO header).
Features
- 16 data outputs for LED strips including GND and 5V. All outputs receive data in parallel.
- Input power (5V) operates level shifter as well as the Raspberry Pi; no separate USB supply needed.
- Fused 5V outputs on connectors to prevent accidents.
- The pins of the I²C, UART and system-SPI busses (including both CS-lines) of the Raspberry Pi are not occupied by the data lines. They are broken out and allow connecting other common peripherals.
The CLK is shared, but each connector gets a dedicated buffered signal.
The 5V output, accessible on each of the 16 connectors, is fused, so that accidental shorts when messing with the LED strip wires in the field do not cause harm.
If you don't need 5V at all (using an external power supply), don't add a fuse. For smaller power use (e.g. active termination), use a 1A fuse. The outputs are beefy enough that they even could support a couple of shorter 5V LED strips directly, in that case use up to 20A fuse. However, generally it is advisable to separately power the strips; 20A only powers 300 LEDs or so.
If there is no fuse, then the 5V connectors are floating, but note that all 5V pins on that rail are connected with each other: if you use multiple external power supplies, only connect GND, not 5V to prevent balancing currents.
BOM
| Count | Type | Package | Info |
|---|---|---|---|
| 4 | 74HCT245 | TSSOP-20 | HCT or AHCT not HC. |
| 4 | 100nF ceramic capacitor | 0805 | One per HCT245 |
| 1 | 22µF ceramic capacitor, 6.3V | 1206 | Stabilizing Pi Power |
| 1 | 20x2 female pin socket | 0.1" raster | to connect to Pi GPIO |
| 16 | 4x1 pin header | 0.1" raster | to connect to LED strips |
| 1 | Fuse holder | for 20mm fuse | Optional (see text) |
Making board
Get a reasonable current version of kicad (or use the shell.nix) and call
makeThis will create the gerbers in pi-adapter-fab/ and also produces
a pi-adapter-fab.zip, ready to be sent to a fab.
It is also shared on OSH Park (not affiliated).
Parts
40| Qty | Value | Footprint | References |
|---|---|---|---|
| 16 | CONN_01X04 | Pin_Headers:Pin_Header_Straight_1x04 | P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12, P13, P14, P15, P16 |
| 4 | 100n | Capacitors_SMD:C_0603 | C1, C2, C3, C4 |
| 4 | 74AHCT245 | Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm | U1, U2, U3, U4 |
| 4 | CONN_01X01 | Connect:1pin | P40, P40, P41, P43 |
| 2 | +5V | Connector_PinHeader_1.00mm:PinHeader_1x01_P1.00mm_Vertical | P30, P32 |
| 2 | GND | Connector_PinHeader_1.00mm:PinHeader_1x01_P1.00mm_Vertical | P31, P33 |
| 1 | 22u | Capacitors_SMD:C_1206_HandSoldering | C6 |
| 1 | 5V | Pin_Headers:Pin_Header_Straight_1x02_Pitch2.54mm | P17 |
| 1 | Conn_02x02_Odd_Even | Pin_Headers:Pin_Header_Straight_2x02_Pitch2.54mm | J1 |
| 1 | I2C | Pin_Headers:Pin_Header_Straight_1x03 | P21 |
| 1 | Pi-GPIO | Connector_PinHeader_2.54mm:PinHeader_2x20_P2.54mm_Vertical | P20 |
| 1 | System SPI | Pin_Headers:Pin_Header_Straight_1x06 | P22 |
| 1 | UART | Pin_Headers:Pin_Header_Straight_1x03 | P23 |
The 39 most common of 40 parts.
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Questions
How big is the Pi adapter hc PCB?
It measures 70 × 56 mm and has 4 copper layers, 1.6 mm thick.
What parts does the Pi adapter hc use?
40 parts, built around the 74AHCT245D and CL31A226MQHNNNE. 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 Pi adapter hc KiCad files?
From the hzeller/spixels repository on GitHub, at the commit this page was made from: the board is hardware/pi-adapter-16-high-current/pi-adapter-hc.kicad_pcb and its schematic hardware/pi-adapter-16-high-current/pi-adapter-hc.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Pi adapter hc design in my own project?
Its repository publishes it under the LGPL-3.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).