Hello everyone,
I have been trying to build an interface for pushpin, with no success
at all. I bought three 6n138's from digikey, and 1k, 200, and 5k6
resistors as well as a 4.7uF electrolytic capacitor from my local
RatShack. I have read all postings to this group as well as ove's
four pushpin-relevant blogposts:
http://gameboygenius.8bitcollective.com/wordpress/?p=95
http://gameboygenius.8bitcollective.com/wordpress/?p=96
http://gameboygenius.8bitcollective.com/wordpress/?p=99
http://gameboygenius.8bitcollective.com/wordpress/?p=103
btw, p=99 isn't tagged with pushpin. The other three are.
I have the japanese version; CGB-JPN-1; it was bought for me when I
was a child, and was sitting in my drawer unused for years until I
heard about LSDj. Since then I have performed the "pro sound" mod on
it. I doubt any of that matters but it never hurts to be thorough.
I have scrutinized bost Bill Byrne's working breadboarded interface
and ove's schematic.
To me it seems like they differ slightly. First off, on pin 2 in
Bill's circuit, it looks like the 200ohm resistor isn't actually
connected. Correct me if I'm wrong, as I may be, but wouldn't wiring
it up like he did just short the leads as that horizontal strip is
just one piece of metal? Wouldn't this make the resistor useless?
Next I noticed that pin 6 of the 6n138 is grounded. Ove's schematic
doesn't show this. Should I ground pin 6 or not?
I also noticed that Vcc and Gnd in bill's circuit are going up, yet SD
is going down; this implies he isn't using the GB to power the
optoisolator. Is that important? Currently I am using Vcc of the
GBC, which my meter says is 4.94v. Am I being silly or is that okay?
Finally, I am using a midi cable that I cut in half, as I don't have
any spare midi jacks. Looking at the male end, from left to right,
pinouts.ru tells me that it's 3,5,2,4,1. It also says that pin 4 is
current source and pin 5 is current sink, so it seems to fit the
schematic. Looking at
pinouts.ru's MidiOut pinout, it is just
horizontally flipped, so I'm thinking I have this right. If someone
could confirm that for me I would appreciate it :)
I have been using ove's sdtest program, and I cannot get *anything*
out of it. If I connect SD to the GB's ground it reads it just fine.
If I connect SD, Vcc, and Gnd of my keyboard (an M-Audio Ozone; though
I have also tried a Korg Electribe-R MKII and a MOTU Fastlane USB) I
get timing and events in sdtest just fine, but only a few, random
notes in pushpin, as ove described.
I have tried all 3 6n138s, hoping that maybe I just fried one, but
nope, none of them did anything.
I tried omitting the 220, I have tried using 1k for R1 and R2 as
someone else with a CGB-JPN-1 described, I have tried with and without
the capacitor, and nothing has worked. I am planning on getting two
10k pots to use for R1 and R2 tomorrow, if I can find the time.
I would *love* to have a midi-capable gameboy, and any hints as to why
my interface is failing so miserably would be highly appreciated.
Many thanks to all who have contributed to this wonderful project :)
-alden