I’ve just build my first Core Module, and i cant find the 6N138, thats why i used an HPCL2231 Optocoupler i still have here at home. it’s nearly pin compatible, i just had to do a little modofication.
The Bootstrap Loader is burned, but i cant load an application correctly. While the Programm is loading he still sends “Request for Upload” SyxString (F0 00 00 7E 40 [device-id] 01 F7). I tried to attach a LED to the optocoupler and it works fine.
My midi hardware on PC is OK.
When i try to do the loopback test without PIC, the PC sends Sysex but i receive strange messages back like: note off..etc. Is it because 6N138 is a darlington opt.?
years before I used the CNY17-II which is also an optocoupler without darlington stage. Unfortunately it didn’t work with all MIDI interfaces, therefore I switched to 6N138.
Maybe the optocoupler is too slow, or - and this would be good news for you - R6 (1.2k) isn’t ideal. Just try different values from 220 Ohm to 10k. If you don’t have them in house, consider that resistors can be chained or wired in parallel to vary the resistance.
Well, if i completely remove R6 the lopp back test works correctly. When i plug in the 18F it doesnt work correctly. I was thinking that R6 is just a pull up resistor and the value isnt important?!?!(Digital values)
the 6n139 also works but i fear if you cant get a 138 you also don’t get a 139. but i have a idea. you could order samples at fairchild. they ship very fast. i got mine within 2 or 3 days.
i don’t believe that this will work because they have stored my adress in their database. i also believe that they will not send me samples anymore this month
try other companies like ti … i don’t know but perhaps they have a equivalent to the 6n138/6n139
just google around a little bit. many big companies are sending samples
i have a problems with the optocoupler(i think):i used a cny17-3 but i don’t know if is good!!because with midi-ox , i receive anything on midi in! (message systex,mios v1-8)
I removed all references to the CNY17 from my website because of the bad experiences with this optocoupler. It doesn’t work together with all MIDI interfaces
