2 layers44.5 × 72.7 mm
OSO SWAT C1-jig
joeycastillo/Sensor-Watch
A board replacement for the classic Casio F-91W wristwatch
28 parts2.1k
2 layers101.4 × 79.1 mm
TK2K EXTENDER
frubem/TK2000_bus_extenderForked from https://codeberg.org/hkzlab/TK2000_bus_extender
- Size
- 101.4 × 79.1 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 28
- Nets
- 66
- Pads
- 288
- Tracks, vias
- 664, 18
- Pours
- 4
- Routed
- Yes
- KiCad
- KiCad 9.0 (file 20241229)
- Created
- 3 Aug 2026
- Updated
- 3 Aug 2026
Overview
TK2K EXTENDER is an open-source printed circuit board by frubem, from the frubem/TK2000_bus_extender repository on GitHub, published under the CC-BY-SA-4.0 licence. It is a 2-layer board of 101.4 × 79.1 mm with 28 parts on 66 nets, routed with 664 tracks and 18 vias.
Its parts include 7 capacitors, 7 connectors and 4 fuses.
README
README.mdTK2000 BUS EXTENDER
DISCLAIMER
Any use of this project is under your own responsibility. You will be responsible of checking the correct construction and functionality of your board. By using this project You will agree that I cannot be held responsible if it will destroy any of your devices, damage your computer, burn down your house or whatever.
Introduction
This board is a bus extender for the TK2000 computer, and allows plugging in up to 3 expansion boards into it.
Differently from what happens in the Apple II, the TK2000 does not differentiate between the expansion slots: every connector brings out the same signals, and it's up to the boards installed in there to decode the signals appropriately and decide which memory/IO range to use.
Hardware
The board was designed with KiCad EDA.
Bill of Materials
| Component | Qty | Type / Value | Notes |
|---|---|---|---|
| P2, P3, P4 | 3 | 50 pin (2x25) female edge connector, 2.54mm pitch | https://aliexpress.com/item/1005008354411366.html |
| P7 | 1 | 50 pin (2x25) pin header | Optional, debug only |
| C1 - C6 | 6 | 10uF/25V+ 1206 MLCC capacitors | |
| F1 | 1 | 1.5A 1812 fuse | |
| F2, F4 | 2 | 0.5A 1206 fuse | |
| F3 | 1 | 0.25A 1206 fuse | |
| C7 | 1 | 100-330pF/16V+ 0805 MLCC capacitor | Optional, introduces a delay in Φ2 signal, improves compatibility with some cards |
Bridge JP1, JP2, JP3 and JP4 to connect the DMA and IRQ passthrough chains.
Ordering the boards
You can order the board for this project at PCBWay and support me or download the gerbers and have them printed wherever you like!!!
Fixes
Rev. 1 and 2
Adding a small 100pF capacitor between Φ2 and GND improves compatibility with 65C22 cards that seemed very sensitive to the speed and type of glue logic used to interface them with the bus.
Rev. 3 has a footprint to install this option capacitor, previous revisions require a mod, where the ground trace is scratched to expose the copper and the cap is soldered to the pin on the underside.
Parts
28| Qty | Value | Footprint | References |
|---|---|---|---|
| 6 | 10uF | Capacitor_SMD:C_1206_3216Metric_Pad1.33x1.80mm_HandSolder | C1, C2, C3, C4, C5, C6 |
| 6 | MountingHole_Pad | MountingHole:MountingHole_3.2mm_M3_ISO7380 | H1, H2, H3, H4, H5, H6 |
| 4 | Jumper_2_Small_Open | Jumper:SolderJumper-2_P1.3mm_Open_RoundedPad1.0x1.5mm | JP1, JP2, JP3, JP4 |
| 2 | 0.5A | Fuse:Fuse_1206_3216Metric_Pad1.42x1.75mm_HandSolder | F2, F4 |
| 1 | +5V | TestPoint:TestPoint_Loop_D3.80mm_Drill2.5mm | J1 |
| 1 | 0.25A | Fuse:Fuse_1206_3216Metric_Pad1.42x1.75mm_HandSolder | F3 |
| 1 | 1.5A | Fuse:Fuse_1812_4532Metric_Pad1.30x3.40mm_HandSolder | F1 |
| 1 | 100pF | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C7 |
| 1 | Debug Pins | TK2000:PinHeader_2x25_P2.54mm_Vertical | P7 |
| 1 | Expansion Edge | TK2000:Conector Edge | P1 |
| 1 | GND | TestPoint:TestPoint_Loop_D3.80mm_Drill2.5mm | J2 |
| 1 | SLOT 1 | TK2000:PinSocket_2x25_P2.54mm_Vertical | P2 |
| 1 | SLOT 2 | TK2000:PinSocket_2x25_P2.54mm_Vertical | P3 |
| 1 | SLOT 3 | TK2000:PinSocket_2x25_P2.54mm_Vertical | P4 |
Questions
How big is the TK2K EXTENDER PCB?
It measures 101.4 × 79.1 mm and has 2 copper layers, 1.6 mm thick.
What parts does the TK2K EXTENDER use?
28 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 TK2K EXTENDER KiCad files?
From the frubem/TK2000_bus_extender repository on GitHub, at the commit this page was made from: the board is TK2K_EXTENDER.kicad_pcb and its schematic TK2K_EXTENDER.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the TK2K EXTENDER design in my own project?
Its repository publishes it under the CC-BY-SA-4.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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