Converts USB MIDI clock messages to sync signals.
- Seeed XIAO RP2040
This project uses Arduino IDE2 and requires the following libraries:
- board: Arduino-pico 4.1.1
- library: Arduino MIDI Library 5.0.2
Build setting:
- Tools->Board:->Raspberry Pi Pico/RP2040->Seed XIAO RP2040
- Tools->USB Stack:->Adafruilt TinyUSB
Complete schematic created in KiCad.
Minimum configuration with sync signal output terminal only
Connects to the sending MIDI device with a USB cable and to the receiving device with a 3.5 mm stereo cable.
The run mode switch can be used to select the action to be taken when a MIDI START/STOP message is received.
The D1 pin is assigned to mode switch. D1 is pulled up and goes High when open.
| D1 | behaviour |
|---|---|
| Low | Sends out or stops the sync signal in conjunction with MIDI Start and Stop messages. |
| High | Free run. When MIDI Clock is received, the Sync signal is sent regardless of the playback status of the MIDI device. |
The DIN SYNC Start/Stop signal is output to the D2 pin. D2 pin is assigned to 'DIN S' on the DIP switch and is connected to the RING of the Sync terminal.
Transfers MIDI messages between USB MIDI and TRS MIDI.
Note:
- SysEx is not supported.
- The clock input from TRS MIDI IN cannot be converted to a Sync signal.
The setting switches can be used to set PPQ values and MIDI filter settings.
| pin | name | setting |
|---|---|---|
| D5 | MODE0 | Type setting L:PPQ values are changed using Setting switch. The value stored in the EEPROM is ignored. H:PPQ values are changed using SysEx messages. Settings are saved in EEPROM. |
| D4 | MODE1 | MODE0=L : PPQ selecter MODE0=H : MIDI FilterSelector |
| D3 | MODE2 | MODE0=L : PPQ selecter MODE0=H : MIDI FilterSelector |
| MODE1 | MODE2 | PPQ |
|---|---|---|
| H(Off) | H(Off) | 1 |
| H(Off) | L(On) | 2 |
| L(On) | H(Off) | 4 |
| L(On) | L(On) | 24 |
| MODE1 | MODE2 | Filter |
|---|---|---|
| H(Off) | H(Off) | All messages are forwarded from USB to TRS MIDI Out |
| H(Off) | L(On) | Only Clock, Start, Stop, Continue are fowarded. |
| L(On) | H(Off) | Foward only clocks |
| L(On) | L(On) | N/A (Reserved) |
In this project, the pulse width of the sync signal is set to 5 ms.
The reason for this is that the KORG specification is 15 ms, but many other companies' devices use 5 ms.
If you want to change this, modify the definition of DEFAULT_SPW to SPW_15MS and rebuild.
The PPQ values can be changed using SysEx messages.
You can specify a value between 1 and 24, but it will not work correctly unless it is a divisor of 24.
The PPQ value is stored in the EEPROM at location 0x00.
| Byte[Hex] | Description |
|---|---|
| F0 | Exclusive Status |
| 7E | non realtime Universal System Exclusive Message |
| 49 | Device ID |
| 0B | File Reference Message |
| 02 | Change (Select or Reselect) |
| nn | PPQ : 1,2,3,4,6,8,0Ch(12),18h(24) |
| F7 | End Of Exclusive |
The Sync signal pulse width can be changed using a SysEx message.
It can be set to 5ms or 15ms.
The Sync signal pulse width value is stored in the EEPROM at location 0x01.
| Byte[Hex] | Description |
|---|---|
| F0 | Exclusive Status |
| 7E | non realtime Universal System Exclusive Message |
| 49 | Device ID |
| 0B | File Reference Message |
| 02 | Change (Select or Reselect) |
| nn | Pulse Width 5ms:3Fh(63), 15ms:5Fh(95), Reserved:7Fh(127) |
| F7 | End Of Exclusive |
SysEx files are stored in assets/sysex. Use as needed.
Note: The SysEx message does not define a dedicated one, but rather diverts the universal system-exclusive File Reference Message.
USB MIDI to Sync Converter is open source and licensed under the GPL3 License.