Hello everybody.
I’m currently building a midibox (32 knobs, a few buttons and a 4x16 LCD) and can’t get the midi-in port to work (hence, no mios on the pic yet).
The connection from the DIN socket to the optocoupler socket is ok (plugged in a led+resistor between pins 2 and 3 of IC2 and it flashed when receiving sysex data).
But that data never gets to the pic, a led+resistor between Vss(#31) and RX(#26) don’t show any visible reaction to sysex data.
when searching the forum for other postings describing the same problem i found a little checklist… quoting from there:
* Check that MIDI interface is working (plug cable midi-out –> midi-in of the pc, compare sent/received byte count) = CHECK
* check polarity of midi cable = CHECK
* check polarity of D1 = was wrong, flipped it around, still the same problem = CHECK
* check output voltage between pin #5 and #6 of IC2: should be 5V, is 0.1V = NO CHECK
i tried two different 6n138s in the socket, both show the same symptoms (so i guess the chip is not the problem).
oh yeah, when i measure resistance between the two pins of R6 (in-circuit but without the pic and the optocoupler) i only get about 800 ohms, not the 1.2k that should actually be there. could this be a problem?
resistance of R5 is okay (5.6k)
it would be so great if someone could help me get from ??? to 8) .