2 layers99.7 × 99.7 mm
VDP Composite
obiwanjacobi/Zalt
Zalt is a home brew Z80 computer with a modern(isch) chipset.
113 parts16
2 layers99.7 × 99.7 mm
Decoder Board
obiwanjacobi/Zalt16Zalt is a home brew Z80 computer with a modern(isch) chipset.
- Size
- 99.7 × 99.7 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 690
- Nets
- 154
- Pads
- 1,127
- Tracks, vias
- 1,308, 151
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 4
- Created
- 28 Jun 2016
- Updated
- 28 Mar 2026
Overview
Decoder Board is an open-source printed circuit board by obiwanjacobi, from the obiwanjacobi/Zalt repository on GitHub. It is a 2-layer board of 99.7 × 99.7 mm with 690 parts on 154 nets, routed with 1,308 tracks and 151 vias.
It is built around the EPM2405SJ. Its parts include 115 resistors, 80 diodes, 13 capacitors, 3 connectors and 2 ICs. It belongs with the retro computing and games and fPGA and programmable logic boards and the FPGA and CPLD boards of this library.
Main components
1README
README.mdZalt
Zalt is a home brew Z80 computer with a modern(isch) chipset.
Zalt Z80 Computer
| Made by Marc Jacobi 2016-2020 |
|---|
| blog: https://jacobielectronix.wordpress.com/category/zalt/ |
| email: obiwanjacobi@hotmail.com |
| Modules: | |
|---|---|
| CPU Board | (v1.0) |
| Decoder Board | (v1.0) |
| BusSpy Board | (no pcb) |
| Folders: | |
|---|---|
| BusSpy Board | module (handwired) |
| CPU Board v1.0 - locked | module (in production) |
| Decoder Board v1.0 - locked | module (in production) |
| VDP Board v1.0 - locked | module (in production) |
| Design | braindump and design documents |
| Kicad | Zalt specific (shared) libraries |
| Kicad/Board Template | PCB template for stackable boards. |
| Kicad/Logical Design | Logical scratch pad for working on ideas. |
| Source | Zalt OS source code |
| Source/Jacobi.Zalt.IntegrationTests | Zim80 tests |
| Source/SystemController | PSoC5 project and source code |
| Source/Z80 Tests | Location for all kinds of test code |
| Source/Zalt Bios | The Zalt OS source code (to be moved) |
| Source/z88dk target | Source for the z88dk Zalt target |
| Under Construction/GPU Board v0.1 | Graphics based on a ARM MCU |
| Under Construction/TTL VGA v.01 | Graphics with TTL/GAL 1st prototype (partially build) |
| Under Construction/TTL VGA v.02 | Graphics with TTL/GAL 2nd prototype |
| Under Construction/ZaltToISA | PC ISA interfacing |
Disclaimer: Only at a very basic level does any of the BIOS code work - see tests. A lot of the source code is still being developed (and changed).
Parts
690| Qty | Value | Footprint | References |
|---|---|---|---|
| 115 | Resistors_SMD:R_0603_HandSoldering | R200, Rs201, Rs202, Rs203, Rs204, Rs205, Rs206, Rs207, Rs208, Rs212, Rs214, Rs215, Rs216, Rs217, Rs218, Rs219 +99 | |
| 80 | Diodes_SMD:SOD-123 | D201, D202, D203, D204, D205, D206, D207, D208, D212, D214, D215, D216, D217, D218, D219, D220 +64 | |
| 11 | 100n | Capacitors_SMD:C_0603_HandSoldering | C102, C103, C201, C202, C203, C204, C205, C206, C207, C208, C209 |
| 4 | P*** | 1pin | 1PIN, 1PIN, 1PIN, 1PIN |
| 1 | 10u | Capacitors_Tantalum_SMD:TantalC_SizeC_EIA-6032_HandSoldering | C101 |
| 1 | 22u | Capacitors_Tantalum_SMD:TantalC_SizeC_EIA-6032_HandSoldering | C104 |
| 1 | AP1117D33 | TO_SOT_Packages_SMD:SOT89-3_Housing_Handsoldering | U202 |
| 1 | BUSHDR-A | Connect:IDC_Header_Straight_40pins | HDR201 |
| 1 | BUSHDR-B | Connect:IDC_Header_Straight_40pins | HDR202 |
| 1 | CONN_01X02 | Connect:PINHEAD1-2 | P201 |
| 1 | DECHDR | Connect:IDC_Header_Straight_40pins | P203 |
| 1 | EPM240 | Housings_QFP:LQFP-100_14x14mm_Pitch0.5mm | U201 |
| 1 | JTAG | Connect:IDC_Header_Straight_10pins | P202 |
The 219 most common of 690 parts.
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Questions
How big is the Decoder Board PCB?
It measures 99.7 × 99.7 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Decoder Board use?
690 parts, built around the EPM2405SJ. 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 Decoder Board KiCad files?
From the obiwanjacobi/Zalt repository on GitHub, at the commit this page was made from: the board is Decoder Board v1.0 - locked/Kicad 4/Decoder Board.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the Decoder Board design in my own project?
Its repository states no licence, so its author keeps all rights: ask obiwanjacobi before reusing the design.