2 layers99.8 × 46.4 mm
2 layers99.8 × 46.4 mm
OmniSCC+
RBSC/OmniSCC23OmniSCC catridge for MSX
- Size
- 99.8 × 46.4 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 29
- Nets
- 92
- Pads
- 231
- Tracks, vias
- 574, 61
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 22 Sep 2026
- Updated
- 27 Oct 2026
Overview
OmniSCC+ is an open-source printed circuit board by RBSC, from the RBSC/OmniSCC repository on GitHub, published under the GPL-3.0 licence. It is a 2-layer board of 99.8 × 46.4 mm with 29 parts on 92 nets, routed with 574 tracks and 61 vias.
It is built around the SN74LVC8T245PW and RB520SM9-30. Its parts include 13 capacitors, 7 resistors, 4 ICs, 3 connectors and 1 diode. It belongs with the retro computing and games boards of this library.
Main components
2README
board/OmniSCC+/README.mdOmniSCC+ — level-shifted board
KiCad 8 project for OmniSCC+: the same 16 MB Raspberry Pi Pico clone, but with SN74LVC8T245 bus transceivers between the RP2040 and the MSX slot, so the MSX sees proper 5 V logic levels on the address, data and control lines.
Revision 1.1
R7 (10 kΩ, 0805) pulls /RES up to +5VA. This hardware change addresses
spontaneous resets observed in USB mode when touching the connector on revision
1.0. Use the revision 1.1 PCB and fabrication archive for new boards.
USB stability fix for revision 1.0
Revision 1.0 has no pull-up resistor on /RES. The floating reset signal can
cause spontaneous resets in USB mode, for example when touching the USB
connector. Add a 10 kΩ resistor between /RES and +5VA to retrofit the
pull-up included as R7 on revision 1.1.
- Disconnect the board from both the MSX and USB before soldering.
- With the board oriented as in the picture, solder the 10 kΩ resistor and connecting wire between the two marked points. The resistor has no polarity.
- Insulate the resistor lead and wire where needed so they cannot short to neighbouring pads or the cartridge edge contacts. Check the solder joints and reconnect USB to verify stable operation.
This is a hardware modification; changing the firmware alone does not add the pull-up. Revision 1.1 already includes R7 and needs no additional resistor.
Files
| File | Contents |
|---|---|
OmniSCC+.kicad_sch / .kicad_pcb / .kicad_pro | Schematic, layout, project |
production/OmniSCCplus_1_1_Gerber.zip | Revision 1.1 Gerbers and drill files (no BOM/CPL) |
production/netlist.ipc | Revision 1.1 IPC-D-356 netlist for electrical test |
fabrication-toolkit-options.json | KiCad Fabrication Toolkit settings used to generate the ZIP |
Datasheets/OmniSCC+-v1.0-schematic.pdf | Historical revision 1.0 schematic; use the KiCad schematic for 1.1 |
Datasheets/RPPICOPURPLE-pin-1024x438.jpg | Pinout of the 16 MB Pico clone |
../../LICENSE | Project license |
The old production/OmniSCCplus_1_0_Gerber.zip and production/v1.0/ assembly
CSVs are retained for revision 1.0 only. They must not be used to assemble 1.1:
component positions changed and R7 was added. Generate new assembly exports
from the revision 1.1 KiCad project when needed.
Symbols and footprints come from the OSPC library (OSPC_Library); configure it before opening the project.
Differences from the base board
- Level shifters on the whole bus instead of a direct 3.3 V connection.
- No option jumpers. GP26 is
AUDIO, GP27 is the data transceiver direction (DATA_DIR), GP28 is/WAIT./IORQ,/BUSDIR,/M1and/INTare not routed to the RP2040.
Build the firmware for this board with -DPICO_BOARD=omniscc_plus, which
defines WITH_SHIFTERS.
Parts
29| Qty | Value | Footprint | References |
|---|---|---|---|
| 9 | 0.1uF | Capacitor_SMD:C_0805_2012Metric | C2, C3, C4, C5, C6, C7, C8, C9, C10 |
| 4 | 10K | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R1, R2, R3, R7 |
| 4 | SN74LVC8T245 | Package_SO:TSSOP-24_4.4x7.8mm_P0.65mm | U1, U2, U3, U4 |
| 2 | Conn_01x20 | Connector_PinSocket_2.54mm:PinSocket_1x20_P2.54mm_Vertical | J2, J3 |
| 1 | 10nF | Capacitor_SMD:C_0805_2012Metric | C13 |
| 1 | 10uF | Capacitor_SMD:C_0805_2012Metric | C11 |
| 1 | 1K | Resistor_SMD:R_0805_2012Metric | R5 |
| 1 | 22uF | Capacitor_Tantalum_SMD:CP_EIA-3528-21_Kemet-B | C1 |
| 1 | 2N7002 | Package_TO_SOT_SMD:SOT-23 | Q4 |
| 1 | 330 | Resistor_SMD:R_0805_2012Metric | R6 |
| 1 | 4.7nF | Capacitor_SMD:C_0805_2012Metric | C12 |
| 1 | 4K7 | Resistor_SMD:R_0805_2012Metric | R4 |
| 1 | Conn_MSX_BUS_edge | OSPC_Library:MSX_CART_SW_Small | J1 |
| 1 | RB520SM | Diode_SMD:D_SOD-123 | D1 |
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Questions
How big is the OmniSCC+ PCB?
It measures 99.8 × 46.4 mm and has 2 copper layers, 1.6 mm thick.
What parts does the OmniSCC+ use?
29 parts, built around the SN74LVC8T245PW and RB520SM9-30. 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 OmniSCC+ KiCad files?
From the RBSC/OmniSCC repository on GitHub, at the commit this page was made from: the board is board/OmniSCC+/OmniSCC+.kicad_pcb and its schematic board/OmniSCC+/OmniSCC+.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the OmniSCC+ design in my own project?
Its repository publishes it under the GPL-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).