It is necessary. Try a four terminal 3.5mm connector.

Hey guys! sorry again, but i have one more question.... in the original trash80 schematic, there's just 3 wires from the arduino going to the gameboy cable (A0-A1-A2)... but in countless other demos and photos there's also a ground wire running from the GND on the arduino to the gameboy link cable as well....

My question is this:
Is the GND connection necessary for it to run? in my breadboard tests i had the ground wire connected... did not think of trying to remove it. the reason why i'm asking is because of the simplicity of connecting a 3 wire cable to the gameboy (using a simple 3.5mm jack) versus the complexity it is to do a 4 cable one (another DIN or a ps/2)...
i'm planning a trip to the electronics store tomorrow morning and i don't have time to rewire everything just to test that out.. if someone could have a quick answer that would be great thanks!

you know what? i think you're absolutely right...i've been avoiding these tiny ones just because if the lack of usb port, but i realize that i can set up one of my 2 arduino boards to program them like you said... and for the price there's no reason not to do that. definitely will save on some added part headaches like the crystals and caps and voltage regulator.. probably will cost me more to buy the parts separately than this and will take more space!

From now on i'll use the main UNO board for prototyping and i'll buy a bunch of these small pro minis for the final projects!

thanks for the advice

in addition to V reg (wont need that tho' if you tap the GB's 5v) ,  you WILL need the crystal/ resonator circuit.  While, you could build it all point to point on a socket or something; Id suggest one of these:

Arduino pro mini.  All in one  postage stamp - sized  package  (well maybe 2 stamps)
http://www.ebay.com/itm/Pro-Mini-Enhanc … SwT6pV5YIu

So tiny-   and flat.   will be much easier to fit inside somewhere in the GB and will save you lots of wiring, debugging headache.

you can find them from US sellers for almost as cheap.   youll also need a ftdi to usb programmer.     Last time i ordered a bunch of Pro mini's, a programmer was included as a bonus.     like 18$ (shipped)  for 5 of them.            (you can also use a UNO to program in , but it is kinda a pain)

awesome! exactly what i wanted to hear thanks for confirming my hunch

Once i have it built i'll share it along as well....

I might do a build video too... (it's always fun to film stuff)

Those pins are just being used as digital outputs, so no special care is needed. Connect AVcc directly to Vcc and leave AREF unconnected.

hey so i'm building a standalong board with the atmega 328 chip from an arduinoboard flashed with the arduinoboy sketch. trying to make a small as possible board (i could probably do a smaller one with a arduino micro or something but i only have the large atmega chips on hand)

Since i'm planning on using the chip off the board i was looking at its wiring and noticed something on the arduino website:

"Pin 21 - AREF - Analog reference pin for ADC
Pin 20 - AVcc - Suppply voltage for the ADC converter. Needs to be connected to power if ADC isn't being used and to power via a low-pass filter if it is (a low pass filter is a circuit that reduces noise from the power source. This example isn't using one)"

i know the arduinoboy uses the A0-1-2 pins as output to the gameboy. correct me if i'm wrong but that means that those pins behave as digital pins not analog am i right?

does that mean i can negate doing any AREF and AVcc low pass filtering like mentioned on the site? i can just use the barebones circuit (crystal + 2x22pico caps) (maybe the reset button as well... not even sure i need that)

i'll probably need to add a voltage regulatoras well... planning on using a 9V dc battery to power the circuit. it'll be in its standalone box (not integrated in the GB)

Here is a video i did of the test circuit wired with a breadboard (for fun)
https://www.youtube.com/watch?v=wNsFlE-srX0