1 Reply by toomuchjuice

(22 replies, posted in Nintendo Consoles)

been working more on this, but definitely need some outside expertise

i connected a desoldered output cable to a 4021 by attaching the colored wires to the directly to the usual pins: Y-3, O-9, R-10, B-11, W-16 (where the A button pin is 1 and the Vdd pin is 16). with just this i could successfully control a NES by tapping on pin 4 for up, pin 5 for down, etc. i assume this was me grounding each pin.

with only an unmodified controller plugged into the NES, I got normal behavior. when i piggybacked the modified chip on top of the controller chip, i got undefined behavior, usually as if someone was constantly pressing up. this happened even without plugging in the output cable from the modified chip.

this led to further experimentation. i started with a controller and a 4021. stacking the 4021 on the controller chip, with every 4021 pin touching its counterpart, led to normal behavior in the controller. i then bent back one pin at a time on the 4021, testing the piggybacked combination each time. the controller chip and the 4021 were thus connected on one fewer pin with each iteration.

16 shared; none unshared -- normal behavior
15 shared; Data (pin3) unshared -- normal
14 shared; Data (pin3), GND (pin11) unshared -- normal
13 shared; Data (pin3), GND (pin11), CLK (pin10) unshared -- normal
12 shared; Data (pin3), GND (pin11), CLK (pin10), Latch (pin9) -- error

on that last iteration, the controller again behaved as if someone was pressing and holding the up button. thoughts? is the latch indeed responsible? would i correct this behavior by bending the power supply pin on the 4021?

just saw during preview reply that nickmaynard got this exact arrangement to work; now i'm really stumped. does yours work with either controller plugged in to a system and the other not? how about both into the same NES?

edit: i realized during dinner that i am a dumbass and didn't unify grounds on this last iteration. let's see if that helps

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2 Reply by toomuchjuice

(22 replies, posted in Nintendo Consoles)

i executed the plan with mixed results. the original controller still works correctly, but the secondary chip's output controller did not function at all. although the voltages appeared to correct on their way in to the second chip, no button presses registered. suspicion falls on the data output connection or pin, but there were so many soldered connections and opportunities for damage to the chip it seems impossible to say for sure. it was a good trial run, and for my second attempt i will try to remove some variables and headache by using some unattached controller chips. will something like this function the same as an authentic NES controller chip? even though we have plenty i hate tearing up functional controllers, and am skeptical about scrounging parts from dysfunctional ones.

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3 Reply by toomuchjuice

(22 replies, posted in Nintendo Consoles)

all right will be doing this when i'm done with work for the day. have a question or two more.

first off, although i understand the concept behind the idea, i was a bit confused by the pin numbers given. for the purposes of absolute clarity below is a graphic of a second, standalone chip i am planning to piggyback onto a first, still-embedded-in-a-controller chip . the check marks indicate the pins i intend to connect to a second output cord; all others will be connected to the corresponding pin on the first chip.

image hosting

because i'd like to know exactly what's going on here, would someone please be so kind as to point out any flaws in my understanding here. with the addition of the second chip, we are trying to set up two separate master/slave relationships from nes 1 to chip 1 and nes 2 (or usb device) to chip 2. all the button-press pins should be directly connected to achieve synchronized 'inputs' to the two chips. any pins on chip 2 associated with communication with nes 2 (i.e. all five colored wires) should be independent of the first chip, because the second system will be querying the controller state independently of the first system. on this last point, i am a particularly uncertain about the power supply connection. also, would it be acceptable/advisable to fully connect the following: brown output wire 2 to 'brown' pin on chip 2 to 'brown' pin on chip 1 to brown output wire 1 (in order to connect grounds)? sorry if this is hand-holding stuff; i will make sure to produce to justify your effort

damn one last question: known risks of damaging a 4021 chip with heat when removing from board with a soldering iron?

image from http://claymore.engineer.gvsu.edu/~kowa … roject.htm

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4 Reply by toomuchjuice

(22 replies, posted in Nintendo Consoles)

damn quick. fair enough. i'll give it a go monday.

in the interim, any special tips for a) removing a chip from the controller board or b) physical arrangement of the two-chip setup? I've done a decent amount of soldering, but generally planned circuits from scratch on blank breadboards type stuff...not used to working with printed circuit boards, let alone such classic prefabs, so any headache savers would be much appreciated

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5 Reply by toomuchjuice

(22 replies, posted in Nintendo Consoles)

hi there. consulted the internet after running into a similar need and doing a simple splice of matching colors, and found this, pretty much the only relevant thread anywhere. thought it would be okay to resurrect if i had something to contribute

a brief description of the performance of the spliced outputs for anyone interested: plugging one or the other output into the standard original nes console produced normal behavior. plugging both outputs into the same console also produced normal behavior, rather than the double-tapping i was naively expecting. starting with only one output plugged into a powered-on system, plugging the second output into a second, powered-off console locked the controller (i believe it froze as if down was permanently pressed) and lit up the power LED on the second console; unplugging that second output from the second console would then restore normal behavior. plugging both outputs into separate powered-off consoles and then turning them on simultaneously produced hilarious and bizarre glitches, usually with one, character-sized symbol wallpapered across the screen.

anyway, i'd expected the separate power supplies to be an issue, but now i see that it is not as simple as removing a superfluous +5 VDC connection. the suggestion nitro made about adding another chip seemed rather clever. i have the capacity to perform that experiment, but was wondering if anyone would be willing to verify the theory and confirm the pin numbers given before i did all that soldering. the solution sounded good to me, and if anyone can second it, i'll be happy to try it out and post the results here. thanks very much.

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