KA12 – Serial port MIDI interface
Features
- 1 × MIDI IN, 1 × MIDI OUT.
- Durable metal die cast DIN 5 plugs with rubber strain reliefs.
- Cable length: 1.4 meter (4.5 ft) each.
- 2×0.25 mm² (AWG 23) shielded cables.
- Interface is contained inside serial port DB25 plug.
- Durable construction, modern electronic design, SMT mounted.
- Fast optocoupler with high current transfer ratio.
- Fully compatible with existing software, no additional drivers needed.
Photos
Short manual
- Interface should be connected to Amiga only if the computer is turned off.
- MIDI links are optoisolated, so MIDI plugs may be connected to devices even when everything is turned on, without risk of hardware damages. However "hot switching" of running MIDI data streams may result in unpredictable effects and is not recommended.
- MIDI IN interface plug, marked black, should be connected to device sending MIDI messages (keyboard, controller), to its MIDI OUT socket.
- MIDI OUT interface plug, marked red, should be connected to device receiving
MIDI messages (synthesizer, sound module), to its MIDI IN socket.
- Wrong connection (input to input, output to output) is not dangerous to hardware, but obviously won't work.
- Programs (usually games) sending MIDI messages directly to Amiga serial port, work with KA12 without any driver.
- Programs accessing MIDI through camd.library do not need any drivers for KA12 as well. Serial port interface driver is embedded in camd.library. The library is usually installed with MIDI applications, it may be also downloaded from Aminet.
Schematic diagram
The following files and data related to KA12 serial port MIDI interface by Grzegorz Kraszewski are licensed under Creative Commons Attribution 4.0 International 
Project files
- RastPort repository on GitHub
- Archived KiCAD 6.0 project, schematic and PCB (ZIP archive, 41 kB)
- PCB Gerber files (ZIP archive, 12 kB)
Bill of materials
| Reference | Description | Quantity |
|---|---|---|
| – | PCB | 1 |
| U1 | Dual RS232 transmitter/receiver; MAX232A, ST232C or equivalent; SO16 | 1 |
| U2 | +5 V fixed voltage regulator; ST78L05 or equivalent; SO8 | 1 |
| U3 | Optocoupler; IL207 or MOC207; SO8 | 1 |
| D1 | Switching diode; 1N4148; 1206 | 1 |
| C1-C6 | MLCC capacitor; 100 nF, 50 V, X7R, ±10%; 1206 | 6 |
| C7 | MLCC capacitor; 100 pF, 50 V, C0G, ±10%; 1206 | 1 |
| R1, R3, R4 | Thick film resistor; 220 Ω, 0.25 W, ±5%; 1206 | 3 |
| R2 | Thick film resistor; 3.3 kΩ, 0.25 W, ±5%; 1206 | 1 |
| CN1 | D-Sub 25 pin female plug, for cable | 1 |
| CN1 | D-Sub 25 pin shell | 1 |
| – | Data transmission cable, LiYCY 2 × 0.25 mm², braided shield | 3 m |
| – | DIN 5 plug, Rean NYS322 | 2 |
| – | Heat shrink tube 1.6 mm, black | 16 mm |
| – | Heat shrink tube 4.8 mm, black | 90 mm |
| – | Heat shrink tube 4.8 mm, red | 90 mm |
| – | Plastic transparent fuel pipe 7/10 mm | 30 mm |