midi in not working

[Guest LittleLui]

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) .

[TK.]

check output voltage between pin #5 and #6 of IC2: should be 5V, is 0.1V = NO CHECK

no, it behaves correctly.

A much more detailed list + schematics with measuring points can be found here:

http://www.ucapps.de/howto_debug_midi.html

Best Regards, Thorsten.

[Guest LittleLui]

Just found out i forogt to cut a few tracks. Damn that stripboard, next time i'll use a PCB;D.

Thanks for the quick answer though, Thorsten!