2 layers40.3 × 75.7 mm
2 layers32.4 × 25.5 mm
USD Turbo
68ec020/uSD-Turbo1TurboMMC uSD card interface for the BBC Micro and MMFS
- Size
- 32.4 × 25.5 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 15
- Nets
- 23
- Pads
- 75
- Tracks, vias
- 159, 33
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 7 (file 20221018)
- Created
- 18 Aug 2023
- Updated
- 27 Jul 2026
Overview
USD Turbo is an open-source printed circuit board by 68ec020, from the 68ec020/uSD-Turbo repository on GitHub, published under the GPL-2.0 licence. It is a 2-layer board of 32.4 × 25.5 mm with 15 parts on 23 nets, routed with 159 tracks and 33 vias.
It is built around the 74LVC125AD and AMS1117-3.3. Its parts include 5 capacitors, 5 resistors, 2 ICs, 1 diode and 1 connector. It belongs with the interfaces and adapters boards of this library.
Main components
2
74LVC125AD
SOP-14L-40℃~+125℃ 1 1.65V~5.5V 2.6ns@5V,15pF 4 40uA 50mA 50mA 74LVC Schmitt trigger Tri-State Unidirectional SOP-14L Buffers, Drivers, Receivers, Transceivers ROHSMDDBuffers, Drivers, Receivers, Transceivers
AMS1117-3.3
SOT-223-40℃~+125℃ 0.003%Vout 1 1.1V@(800mA) 15V 1A 3.3V 5mA 72dB@(120Hz) Fixed Over Current Protection、Short Circuit Protection、Thermal shutdown Positive SOT-223 Voltage Regulators - Linear, Low Drop Out (LDO) Regulators ROHSAdvanced Monolithic SystemsVoltage Regulators - Linear, Low Drop Out (LDO) Regulators
README
README.mdBBC Micro TurboMMC Interface
Use with https://github.com/hoglet67/MMFS
Inspired by http://stardot.org.uk/forums/viewtopic.php?t=9445&f=3#p110691
The interface works in my BBC Micro. I included resistors everywhere two outputs could be active at the same time, like in the hand-drawn schematic. So, it should be safe. But: Use at your own risk!
Changes compared to the hand-drawn schematic
- active level shifters (74LVC125AD) instead of voltage dividers
- 3.3 V voltage regulator
- no pull-ups on PB2, PB3, PB4, marked with VDD ? in the hand-drawn schematic (maybe I should add them, if the port is configured as input)
Build your own
I ordered PCBs from JLCPCB. Just use the file jlcpcb/production_files/GERBER-uSD-Turbo.zip
Use the HTML-based BOM tool in /bom
I bought a microSD card slot on eBay, but I don't have a specific part number.
Make sure the right-angle connector is mounted like in the 3D rendering. Pin 1 is the square pad. Make sure this corresponds with pin 1 of your port!
Parts
15| Qty | Value | Footprint | References |
|---|---|---|---|
| 5 | C | Capacitor_SMD:C_0603_1608Metric | C1, C2, C3, C4, C5 |
| 4 | 56 Ω | Resistor_SMD:R_0603_1608Metric | R1, R2, R3, R5 |
| 1 | 1k | Resistor_SMD:R_0603_1608Metric | R4 |
| 1 | 74LVC125AD | Package_SO:SOIC-14_3.9x8.7mm_P1.27mm | U1 |
| 1 | AMS1117-3.3 | Package_TO_SOT_SMD:SOT-223-3_TabPin2 | U2 |
| 1 | LED | LED_SMD:LED_0603_1608Metric | D1 |
| 1 | User Port | Connector_PinSocket_2.54mm:PinSocket_2x10_P2.54mm_Horizontal | J1 |
| 1 | uSD Card | footprints:Conn_uSDcard | XS1 |
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Questions
How big is the USD Turbo PCB?
It measures 32.4 × 25.5 mm and has 2 copper layers, 1.6 mm thick.
What parts does the USD Turbo use?
15 parts, built around the 74LVC125AD and AMS1117-3.3. 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 USD Turbo KiCad files?
From the 68ec020/uSD-Turbo repository on GitHub, at the commit this page was made from: the board is uSD-Turbo.kicad_pcb and its schematic uSD-Turbo.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the USD Turbo design in my own project?
Its repository publishes it under the GPL-2.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).