v2.1 Running status update

An issue was spotted with the previous release and some keyboards' use of running status. This should be fixed in this version. If everything's working for you leave as is. If not, update to this version using the debug header and appropriate programmer.

V2.0 2023 "Studio" release

The previous version has been used for several years now, but recently it came to light that it didn't cope very well in a situation when there was a MIDI clock running. Originally designed simply to enable MIDI keyboards to be used in place of a Music 4000 keyboard, this wasn't a situation that the firmware had been pitted against. This new version has been reworked to reduce any latency around receiving and processing the MIDI stream, and also attempts to ensure better compatibility with some more esoteric MIDI messages that may be be encountered if plugged into a studio MIDI chain. Feedback is always welcome.

MIDI - Hybrid Music 4000

MIDI channel can now be selected by pressing a button (connected to PA5 and ground). This lights an LED on PA4 (active low, via 560R resistor), and the next midi command received (usually a note) sets the channel. Pressing the button twice causes the channel to be ignored (this is the default state).

Note the requirement for a pullup resistor (10k) to 5V on B13 to ensure the clock on the SPI works properly.

Minor update to 0.3 to implement software debounce for the channel select button.

MIDI to Hybrid Music 4000 for STM32F103

5V tolerant on everything now (managed to make a couple of boo-boos!), pin assignments as follows:
Pins used: Userport PB0-7 (even pins 6-20) are on GPIOs PB4,6-12
Userport CB1 (pin 2) -> Clk, GPIO PB13 (SPI2) - add external 10k pullup to 5V
Userport CB2 (pin 4) -> MOSI, GPIO PB15 (SPI2)
MIDI serial in (3.3V) -> GPIO PA3 (USART2)

All feedback gratefully received!

MIDI to Hybrid Music 4000 for STM32F103

Pin assignments are described in the code. Further testing required with different equipment, but this can be considered fully functional.