CORE MIDI in Problem

Testing/Troubleshooting
1

Sorry it’s the same old tune, but I’m stuck here and the FAQ hasn’t solved my problem yet.

I’ve tested with my voltmeter and seems like I’m getting great and useful voltage fluctuations across IC1 31->26 when SysEx messages are incoming, and no fluctuation when there are no messages.  Wonderful.  

However, I’m not seeing any confirmation messages from the CORE module and the MIOS isn’t getting uploaded.

The PIC is one burned by SmashMouth with bootstrap loader 1.1b and code 0x0000…0000, and it’s sending me ‘Please upload something!’ messages, but not ‘ok, received this bit, a-ok!’ messages.

I’m pretty sure my optocoupler and/or its socket aren’t the problem, either, since I’ve tested continuity and voltages and I’ve tried two different optocouplers in the socket, with the same (seemingly correct) results.

I’m getting constant fluctuations across the important pins on the M-Audio MIDISport UNO’s MIDI-in plugged into my Mac,  even with no MIDI-out plugged in(so I don’t think it’s a MIDI-thru issue)… but since the PIC doesn’t seem to see these useless fluctuations, I doubt that’s a problem.

I’ve checked my MIDI interface using a loopback test and it checked out ok.

I’ve also tested voltages across:  

IC1(31)-IC1(26), oscillating between 60 and 80 mV when SysExen are incoming, and staying at 80 mV at other times.

IC1(31)-IC2(06), with the same results as above.

IC1(31)-IC2(08), 5V all the time.

mbhp_core_extract_opto_test: 80 mV when M- was open, 40 or 60(can’t remember which) when M- was grounded.

Once I get an IC extractor(my hands are inferior at taking out ICs; I invariably mangle some pins), I’ll try mbhp_core_extract_io_loopback and mbhp_core_opto_test, in that order.  But I think my problem might be something simpler.  Perhaps someone can lend me some advice?

And yes, I tried switching polarity on my MIDI-in and had no luck. (:

2

The funny about switching the polarity of the Midi In is: If its the wrong way, you kill the optocoupler pretty sure!  ;D

Always have some spare optos @ home… and try to get the polarity right …  ;)

So: Get a new optocoupler and try it again with that one… hope it works out.

btw hint: Try to get those ICs out with a knife (sliding under it and bending it *smoothly* out of there) - worked out well for me up to now…

Greetz

3

Gaaaaack!! No kidding? There really ought to be a warning about that. ^^;; Looks like I’m taking a trip to the electronics store today.

I’ll try a new optocoupler and see how it works out.  Grm…

I’m used to software.  Any way I can use a revision control system with my board? ^_^;;

Thanks for the tip, pay_c.

4

hm..you could kill the opto when switching the polarity. but i don’t think so. mine was also connected wrong a few times when debugging but it’s already working.

hints as ever for the troubleshooting:

check for shorts and especially cold solders

check the polarity of the diode and if you’re able to check if its working.