MIDI Filter

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.

midi filter

The Outside

midi filter

The Inside

The Schematic

midi thru

Source Code