Just found this great forum and noticed there are plenty others who have been wondering how to add usable controllers to the C64Mini. I see I'm not the only one having added a DE-9 connector inside the stock controller, but I think my instructions might have some extra info that could be logger here too.
I never expected the stock controller would be worth something, so when clicking "Confirm purchase" on this item I already knew I'll be needing a screwdriver and soldering iron soon. USB gamepads obviously are closer to heresy than the answer, no other acceptable options than real 80's digital joysticks like my trusty Prof Competitions (oops, I really am trying to avoid religious conflict, and sincerely do respect anybody's devotion to TAC-2 (no feeling at all IMHO but guess I don't need to understand:)).
Nothing special - just wired the connector, added some pull-up resistors (1.6 kohm worked, 11.2k not, didn't try anything in between) as the chip didn't tolerate increasing wire length too well and dremeled a hole for the connector in the case. While there, did some reverse engineering to document it and figure out, if it would be viable to crop the joystick board to a small adapter that could be built into the C64Mini case (would, but not too high on my to-do list).
I have made the same work but used 10k Ohm "pull-up "resistors, which works fine. These resistors are absolutly necessary, Without the joystick "hangs" in any direction and can not moved again to another direction..
I did this with my joystick but cut the Atari plug off the wire(DB9) of it so it was shorter, are the 1.6 k ohm resistors so you can use the DB9 connector..? I remember when the wire was too long and it would just keep going left continuously. I am glad someone figured it out..
We uses to do this on the C64 DTV too cause its the same Joystick. you could probably fit the board from thec64 mini in thec64 Joystick if you wanted to and make a New version of the C64DTV, THEC64DTV2..
Well THEC64 is made by the same people who made C64DTV.
This is the best way to use a (broken) original USB-Joystick of the C64 Mini or Maxi. You can use your preferred joystick with DB-9 connector and also use the additional buttons A,B,C,D for menu etc. For the correct pin connections see the pictures above!!
Yeah its a good idea well done.. , and as well this way don't use alot of power from the USB connector like some of the USB to DB9 adaptors do, plus you use can still use the 4 red buttons too, A B C Menu buttons.
Better use resistors with a higher value between 5k Ohm up to 10k Ohm. The current I if a button is pressed will be less (I=U/R). With U=3.3V and R= 1.6k Ohm I = 2.1 mA; with 10k Ohm I= 0.33mA !!
So what resistors you need is 5 5 or 10k Ohm resistors then..?
The post on the other site looks like he's uses 1.6k Ohm...
First wired a D9 female to the test pads - worked, kind of. Especially right clicks jammed the direction to right, successive left or right clicks randomly ending the state. Checked wirings, all correct, apparently the chip doesn't tolerate long cables (~1 meter...) too well. Pull-ups to be added,
checked with the first ~10 Kohm resistors I found, 11.2 K they were, no help. Testing L&R with 1.6 K, worked fine, cleaned up and added the rest: Note that the pull-ups are connected to 3V3 (generated by the chip) and not 5V, as that's how the internal buttons are wired and the chip might not tolerate 5V. For long runs you'd generally add 10-20 pF capacitors to ground, but decided 1 meter isn't long enough to require them.
The resistors in the photos are 1.6 K ohm that's soldered to thec64 Joystick board.. only needs a higher resistor if you use a joystick with a longer lead that's over 1 meter(6 Foot) and most are not. and looks like he had a problem with resistors with 11.2 K ohm and they didn't work.
Any resistor value between 5000 Ohm and 10ooo Ohm will be okay. I have used 10000 Ohm (brown, black, black, gold) and it works perfekt with all my old DB9 Joysticks, I still have from old days. It even works with an in-between d-9 auto-fire adapter, i had soldered over 25 years ago for my C64!!
I prefer the higher valuses because of the lower current they will produce. But maybe 1.6k Ohm is also usable but not lower!