MIDI

Description

MIDI devices are very easy to connect to DS via DSerial. MIDI Out can be directly wired to the connector without any components. MIDI In requires to use an Optocoupler, but the schematic is quite simple.

The signal lines should be connected to DSerial CMOS-level UART at IO2 connector (do not use RS-232). Sending and receiving is done using the UART commands. Make sure to set baud rate to 31250bps as this is what MIDI is using.

Here is some sample code to send a note: <cpp> void midiWrite(u8 message, u8 data1, u8 data2) { u8 buffer[3]; buffer[0] = message; buffer[1] = data1; buffer[2] = data2; dseUartSendBuffer((char *) buffer, 3, true); /* blocking UART send */ }

/* then somewhere else do: */

dseSetModes(0); /* Disable RS-232 */ dseUartSetBaudrate(31250); /* MIDI baudrate is 31250 bps */

midiWrite(0x90, 0x11, 0x22); /* send a note to MIDI keyboard */ </cpp>

Schematic

DSerial MIDI In/Out Schematic

Parts

• FOD260L optocoupler (3.3V, most other optocouplers are 5V...)
• 1N4148 switching diode
• ~1 kOhm resistor
• 220 Ohm resistor.

Pictures

MIDI cables connected to DSerial

MIDI Input requires an Optocoupler IC

Small PCB for MIDI input

MIDI keyboard connected to DSerial

PCB

Component placement

PCB 600dpi