Belkin N50 analogue & keyswitch mod

[Pistol451]

Inspired by @tuffrabit's YouTube mod videos, I decided to try my hand at putting together an analogue-stick equipped keypad! Managed to get hold of a Belkin N50 with a non-functioning Dpad, so ideal for this purpose. I've seen any number of modded N52s, and the subsequent Razer versions, but not an N50, so I thought it might be worth documenting the process in case it's useful for anyone else!

For reference, I found the following instructable useful for disassembly info and to get an idea of what the internals look like: https://www.instructables.com/Belkin-Nostromo-N50-mod-left-handed/

I had originally planned on mounting the stick on the Dpad PCB, unfortunately there wasn't enough clearance, and there's no room to extend further into the body - the Dpad PCB is already flush with the base, if you can make it out from this shot:


The Dpad assembly is pretty easy to remove, looks like plenty of space inside:


It looks as though, if I dremel away some of the Dpad supports, I can wedge the stick in there against the backplate...


...yep, that fits a treat!


More to come later!

[Pistol451]

You'll note from the previous post that I've basically dremelled out the opening to be the same size as the circular gate on the analogue stick. It's not ideal, as there's basically nothing stopping dust and crap from getting into the innards of the stick; but, I can't really do much else at this point without coming up with a totally different mounting method. That's not impossible, but for now I may just accept that I'll likely have to change the stick every so often if it gets gummed up inside.

Here's what it looks like with a thumbstick on:


Most of the dust protection dome will have to be removed for it to actually rotate, so that won't help keep the guts clean. I did wonder about those weird "aim assist" rubber boots you can get but we'll see. Anyway, ergonomically it feels great so once it's all up and running I expect great things

The throttle wheel potentiometer does clash with the stick body, so that's had to come out; one of the wires was detached anyway, so I just snipped it off. I wasn't convinced that a throttle wheel would be much use on this device anyway, but I must admit once I got it in my hands, the position of it feels OK. I had considered putting some momentary switches in the hole vacated by the wheel, but I think that would look a bit shonky and they'd be hard to press in that location anyway. I ordered a 6mm shaft ALPS rotary encoder to replace the bulky pot, that will fit in place without clashing, and should be able to be wired up to the teensy as a scroll wheel; how PC games will deal with two scroll wheels I don't know, but anyway that's a nice to have for the future when I get the programming for it sorted out.

How much rewiring I do internally will be determined by whether I keep the N50 PCB in place or not. The main advantage of keeping it in play would be that it would minimise the amount of wiring I have to do (I am not skilled at soldering!), and I would be able to use the Belkin software for mapping the keys, including setting up shift states. The main advantage of ditching it would be that I can just have the Teensy LC doing everything and just one USB cable coming out of the thing, also the PC would just see one controller so it should minimise compatibility issues. So, I thought I'd assemble the device and see if the original PCB worked.

Connecting it to the PC seemed to go OK - the LEDs lit up briefly, it was recognized as a controller, and drivers seemed to get installed OK. Fired up notepad to see if the keys functioned as keys - nothing. So, I tried joy.cpl, which showed it as a 3 axis 10 button controller; but, in the test panel, nothing functioned. Bear in mind that right now the only thing connected to the PCB is the keypad, as the throttle and Dpad are cut away! So, now I have no idea whether the PCB is fritzed, or whether it's just the keypad membrane that is dodgy.

I wasn't planning on keeping the dead flesh rubber dome keypad anyway, so next on the agenda is fitting Cherry MX keyswitches (blues - I know, I know, but this is being done on a tight budget and they were cheap!!) and wiring them up in a matrix. I'm thinking that I should just copy the matrix from the existing membrane, so I can wire into the N50 PCB to test it again, without needing to add resistors and diodes (they're already built into the PCB). However, I'm struggling to trace all the lines on the membrane  I might need a bit of help here!! I'll post some decent quality images of the membrane tonight, if anyone could help me trace it out and come up with the matrix wiring for the keyswitches, that'd be great.

If it turns out the PCB still doesn't work with the Cherries wired in, I'll have to bite the bullet and go full Teensy control - which is where I'll also need to figure out resistors and diodes. Again, any help gratefully appreciated 

[Pistol451]

Did some more testing and the N50 PCB appears to be fritzed. Can't get any button responses out of it, so it's out of the picture - going full Teensy LC. That means wiring up a keyswitch matrix with diodes - think I'm OK with that, we'll see anyway... have to cut the holes for the Cherry MX switches first anyway!

One thing I do need to figure out is the LEDs I'll be adding to the keyswitches. I know I need to add resistors to protect them, but what value?!? It seems unfathomably difficult to actually work it out... From what I've read, it is not a good idea to wire too many LEDs in series. As I will have pairs of red, yellow, green, blue, and purple LEDs (10 LEDs total) it seems wise to wire pairs of the same colour in parallel with the other colours, each pair with its own resistor. But what resistor values? The LEDs I've bought were quoted as 3V forward voltage, but I've read that different colours have different voltages - do I need to tailor the resistances to the LED colours to get consistent brightness? Am I just over-thinking this?!?

[antithesis]

All that aim assist rings do is make the analog stick harder to move and create unpredictable input. I sold them as "stick drift removers" because they are terrible at their stated purpose. I recommend not using one in your project.

[Pistol451]

All that aim assist rings do is make the analog stick harder to move and create unpredictable input. I sold them as "stick drift removers" because they are terrible at their stated purpose. I recommend not using one in your project.

I was thinking of the rubber boot type, cutting them up and just using the upper section, so it hopefully wouldn't affect the stick too much; but I don't think I'll bother, unless I find there is a problem.

[Pistol451]

Progress! I've installed the Cherry keyswitches.



There's a bit of fettling still to do before I can wire everything up: one of the switches isn't quite straight, and a couple are too tight which is squeezing the body of the switch enough to make them stick a bit. It's going to be a bit tight in there with all the wiring for the keyboard matrix and the LEDs; hopefully my soldering won't be too messy 


Keycaps wise, I had planned on re-using the original ones, to keep it looking as stock as possible; I then thought it would be easier just to use some cheap Cherry-compatible ones to save time and effort, however I was shocked at the price of keycaps! So decided to press on with recycling the existing ones. I was inspired by this mod which inserted the posts off salvaged keycaps into the original ones from an N52: https://www.youtube.com/watch?v=YGwiPFXg_e4 Since I don't have any salvaged keycaps, but I do know someone with a 3D printer, I designed some adapters to fit into the N50's keycaps once I'd cut their posts off level with the bottom of the key.



Have to wait until I get a test one printed to see if it works OK.


I did also come up against an issue with the Teensy, which I thought might be worth documenting here, since it wasn't something I had come across in my research beforehand. I had to invert my X and Y axes in the code (thanks for the assistance @tuffrabit!), and after I reflashed the Teensy, it stopped showing up as a controller in joy.cpl!!



Turns out, this is a known issue with Windows - due to some crummy way it manages HID interfaces, it will sometimes just mess up and assign the wrong drivers or something to a previously working Teensy! It can be fixed either by deleting the registry entries associated with the device, or changing the serial number of the Teensy in the sketch. Either way, Windows will then detect it as a new device again and it will work once more. This discussion topic details the method - also confirmed by tuffrabit via email! https://forum.pjrc.com/threads/23566-Teensyduino-USB-Joystick-no-data-driver-problem-workaround

I haven't done that yet, as the PC I'm using to program the Teensy isn't actually the one I need it to work with, so as long as I can continue to flash it there's no real issue for now. Connecting it up to another PC shows it is still working just fine!

[Pistol451]

Bit more progress since the last post. I've now wired up my keyboard rows and columns!



Haven't wired them up to the teensy just yet, and the LEDs are giving me some cause for concern - there's not a lot of space left, so wiring them all up is going to be tricky. I've left that for another day for now!

Another issue I found was that the keyswitch in the top right of the pic clashes slightly with the curved section of the base; not by a lot, but enough to put pressure on it if you try to close the case up tight. There are tiny bumps on each corner of the keyswitches, so I cut that off, and filed it down a tiny bit; that was enough to alleviate the pressure.

When wiring up the keyboard matrix, solid core wire really helps! You can form a little loop in the wire and pop it over the pins, makes soldering them a doddle. Same goes for the diode legs. I had forgotten how hard it is to solder more than two things together, if you're working with stranded wire, twist them together prior to soldering. I used this method to daisy chain as many ground connections together as possible to save on excess wiring.

I've also dry-fitted the encoder wheel, not soldered it yet but with a few modifications it's a good fit, and saves so much space inside!



To make it fit, I had to dremel a small recess in the wheel, and file a bit off the end of the encoder shaft, and a little off the shoulder:


Also needed to shorten the vertical plate on the base that it sits on by a bit. Take this easy, a bit at a time, as you can always take more off but you can't put it back on if you go too far!!



I also decided that the N50 just doesn't have enough keys, so I added a few long shaft tactile switches near the joystick module for some extra buttons:



I think they're a bit too long, but I haven't shortened them yet as I want to see what they're like in use (again, easy to shorten, impossible to lengthen). There's also another button and a status LED in front of the scroll wheel but I haven't wired those up or photographed them yet.

Still a way to go yet, I need to finish connecting everything up and test it all works before I hot glue all the components in place. I think I've figured out the encoder wheel code, so getting that wired up will be a big step forward!