A classic MIDI interface module for Adafruit’s STEMMA interface #STEMMA #Adafruit #MIDI @Adafruit @CedarGroveMakr
Cedar Grove Studios has produced a clever interface board translating between the Adafruit STEMMA I2C interface and a classic MIDI connection.
The STEMMA MIDI interface is a self-powered, one-quarter protoboard-sized module for use with Adafruit STEMMA-compatible products. The interface converts incoming and outgoing classic MIDI current-loop input and output to STEMMA 3.3-volt logic. This interface requires that the host STEMMA interface be placed into UART mode with a fixed rate of 31,250 baud.
The module has two ways to connect UART signals: a STEMMA-compatible 4-pin JST connection is provided on the top edge of the module, and two four-pin strips are available to allow header-style or soldered connections. The header-style connections allow the module to be used with UART signals from sources without a STEMMA interface connector. All power, ground, and RX/TX pins of these connectors are wired in parallel via printed circuit board traces.
The Type B (3.5mm TRS) MIDI input is an optically-isolated Type B 3.5mm TRS connection. The Type B (3.5mm TRS) MIDI output is buffered. On-board receive (RX) and transmit (TX) LEDs indicate incoming and outgoing MIDI signals. Interface module power is supplied by the STEMMA’s 3.3-volt power pin.
The STEMMA MIDI interface was tested with CircuitPython version 3.1.1 and version 4.0.0 Alpha_5. Example test code for the Trellis M4 is provided in the repository.
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