HCPL 2731 optocoupler - MIDI IN frame error

Testing/Troubleshooting
1

is someone using this optocoupler instead of the standard 6n138?

i could not find the 6n here, so i went for this two channel optocoupler…

it has different wiring, but i think i mounted it correcly…

i hooked midi input to pin 1 and 2 (the resisor go to pin 1 and the diode to pin 2 towards pin 1, as in standard 6n wiring)

i connected a 5.6 K on the pin 6 (V02 out) - this seems useless to me, but i mounted anyway

and the pic to pin 7 (V01 out) with the 1.2 K to +5V

pin 3/4 are open

when i try to upload mios using this optocoupler i get the message “MIDI IN frame error”…    ??? ???

but i uploaded mios application in this core module using another working core module and, when i use the 2731 midi in with MIDIOX in this new module, i  can get a “ping” sysex string back after a request… so it seems that “something” is working, but not correctly!

thanks for any help!

it’s the last step to a fully-working AC Sensorizer box!  ;D

2

Hi,

to me it sound like an problem with the output signal of the optocoupler. Try an smaller resistor perhaps 1K or less.

A second thing, perhaps your pic is clocked to slow. So it can be the wrong crystal. But with an feasibility of about 95% it should be a problem with the optocoupler.

Greetings

Markus

3

I take a look at the datasheet, you don´t need the R5 here try 2,2K in stead of 1,2K for R6.

4

i solved by using an old CNY17-2 spared from my old midibox plus… :slight_smile:

i dindt suceed in using the other optocoupler…