This library adds up 4 PIO-based MIDI serial ports to a Rasberry Pi Pico and 6 PIO_based MIDI serial ports to a Raspberry Pi Pico 2. Each serial port has both MIDI IN and MIDI OUT. Data I/O is interrupt driven and is designed to be read and written from a simple loop.
If you need more MIDI OUT than MIDI IN, you can create a PIO MIDI OUT port without creating a MIDI IN port for up to 8 MIDI OUT and no MIDI IN on a Pico and 12 on a Pico 2.
Please report bugs and feature requests as github issues on this project. Pull requests that add features are welcome.
- The MIDI TX signal and MIDI RX signal can be on arbitrary pins.
- The MIDI RX pin of each MIDI UART is configured as an input pin and the MIDI TX pin of each MIDI UART is configured for open drain output.
- The create function automatically allocates a MIDI UART intialized to the correct MIDI baud rate. It uses the first 2 available state machines on the first available PIO.
- The library uses a ring buffer library so there are more than 8 bytes of FIFO between the MIDI UART and the application.
This library API is very similar to midi_uart_lib except it does not use the native hardware UARTs. The advantages of this library are:
- The MIDI TX output is open drain. This makes hardware interface easier.
- RP2040 has only 2 hardware UARTs, and UART0 is often hard-coded for use as the debug console. If you need more than one MIDI UART, this technique is likely your only practical option.
- RP2040 UARTs are always bidirectional. With this library, you may create MIDI OUT ports without creating MIDI IN ports
- Create a subdirectory (e.g.
lib) under your main application library. - Install this library and the ring buffer library as git submodules under the lib directory.
- In your project's
CMakeLists.txtfile addpio_midi_uart_libto thetarget_link_librariesand add the following line
add_subdirectory(${CMAKE_CURRENT_LIST_DIR}/lib/pio_midi_uart_lib)
- Include
pio_midi_uart_lib.hin your application. - Call
pio_midi_uart_create()in your application for each MIDI port you wish to create. - In your application main loop, call
pio_midi_uart_poll_rx_bufferto see if the interrupt handler has loaded any characters to the RX ring buffer. - In your application main loop, add messages to send by calling
pio_midi_uart_write_tx_buffer()and then callpio_midi_uart_drain_tx_buffer()to kick off a new transmission.
The midi-multistream2usbdev project demonstrates creating two bi-directional MIDI ports and 4 MIDI OUT only ports.
If you want to see an 8-IN 8-OUT MIDI interface that uses both this library and midi_uart_lib, check out the pico-usb-midi-interface project.
- If there is a feature request for it, add an API to handle more MIDI IN than MIDI OUT.