MIDI Filters can be used to block a range of MIDI messenges. Mine filters out all messages that don't equal
the channel selected or higher, depending on the single channel switch. The last switch specifies wether to
block messages that aren't note ons. There are pins left over so you can specify further filtering options or
customise the existing ones to suit your needs. I fitted mine into a 118x98x45mm "M3" ABS Plastic Box. I use
low dropout voltage LDOs to provide the 5 volts for the MIDI and the 3.3 volts for the microcontroller. The
buffer chip used must be of the HCT family in order for the 3.3V PIC output to correctly switch the 5V Inverter.
This runs happily off a 9V battery and consumes 6ma.