This is a monodirectional MIDI to RS232 (serial) interface, it play only MIDI to personal PC “RS232″. The MIDI output connector indicated on the left picture  dosen’t work because the buffer inside pic16f84 is too short. source

This circuit is a MIDI interface between drum pads and computer or hardware sequencer. Using this circuit you can hit pads with drumsticks and store the MIDI data in real time.This circuit is based around the PIC16C84 microcontroller which scans the inputs on RB0 to RB7 and when a high is detected the software transmits [...]

This circuit serves as an ultra-low power replacement for multiple LED on-off indicators. It also has the advantage of being easy to read in full daylight. With the parts shown, it is possible to display four bits of information.This circuit use three digits and 2 decimal points for a total of 23 segments. Different groupings [...]

This circuit uses LEDs to display logic states for high, low, rising pulse, and falling pulse, it is generally useful for debugging logic circuitry.This circuit can monitor TTL logic levels. TTL compatible CMOS logic families can also be monitored.This circuit can be built on perforated circuit board and wired by hand. The completed circuit can [...]

This is a low power voltmeter circuit that can be used with alternative energy systems that run on 12 and 24 volt batteries. The voltmeter is an expanded scale type that indicates small voltage steps over the 10 to 16 volt range for 12 volt batteries and over the 22 to 32 volt range for [...]