Build Instructions

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• 1

  The basics - know your options

  In this instruction I will talk about hardware options and potential usage ideas of the components. I will not go in the exact details and scientific explanations - there is not need for it because there are tons of excellent articles about all of them in the net if you want more in depth information about them 
  

  The processing unit

  No matter what kind of function you want to implement, for now, a joystick, gamepad, controller will most likely be a USB Human Interface Device (HID). If you take a look at the USB specifications and how they are implemented - if you are not an absolute nerd or professional programmer - only thinking about implementing this on your own is a nightmare ;). But there are solutions out there that got you covered!

  Right now I know of 2 microcontroller options that can act as an USB HID device out of the box:

  • The Arduino Pro Micro
  • The Tennsy USB development boards

  The Arduino Pro Micro is the cheaper option but it is by far not as powerful as the Teensy 4 (more RAM, higher frequency...)  The good question now is - which to take. Planning to work with multiplexers I played it save a chose the Tennsy to be on the save side. 

   If you have experience with the Pro Micro -> please let me know about it
  

  Important Info: You can buy the boards with or without connectors on them. So if you do not have a soldering iron yet -> buy the preconfigured once! 

  Sticks

  A game controller without any kind of stick - well for me - is not really interesting so we want to have sticks. There are 2 kind of sticks:

  • analog sticks
  • digital sticks

  A digital stick is basically four buttons or micro switches that are triggered by some kind of physical mechanism . A good example is the direction pad on eg. the xbox controllers. Shown in this picture the switches on a salvaged xbox 360 controller

  the characteristic of a normal switch is: it is on - or off ( 0 or 1 - digital..) there is no indication "how hard" the button is pushed.
  Good thing on a custom gaming device -> you can choose in the code what kind of function ( a button press, a keyboard key, a mouse button) it will trigger. So it is pretty easy to build a digital stick on your own. 

  The analog stick on the other hand is build out of at least 2 potentiometers. A potentiometer is basically a variable resistor that will let through more or less voltage. The microcontroller will read that input on an analog pin and will show it as a integer value between 0 and 1023.  For example: If the joystick is in the middle / idle position - x and y axis both show a value round about 512. It might be of by 50 or something, that is not unusual -> that's what analog stick calibration is for :) If you push x axis to the left - value will decrease and reach 0 at the end - moving right it will increase up to 1023

  Very important: most potentiometers used in analog sticks work on a linear scale, meaning the value will steadily increase or decrease along the axis. The other type is logarithmic, meaning that the change of value differs along the axis. Something like this:

  Try to go for linear ones for your project!
  There are ways to transform logarithmic outputs to linear via code or wiring but this is making things very complicated. I had the bad luck that the 3 axis sticks I bought been linear on the x and y axis but logarithmic on the z rotate axis :(

  That said be also be aware that it is no problem at all to make an analog stick behave like a digital one in your code...

  So my recommendation is go for analog sticks only!
  

  But there is another very important limiting factor. Its not like you can add stick after stick and use them as analog axes and get away with it without problems. Windows ( I think it is actually DirectX but not sure about it) can only handle 6 axis! 

  X, Y, Z, Z rotate, Slider left, Slider right 

  So if you plan to use 3 sticks like I do at the moment, it is not possible to use all of them as analog axes. The little stick I use is either used to act as "wasd" input or arrow keys -digital if you like ...

  Potential Use cases for sticks:

  • Have one stick as your classic joystick -> x,y axes and maybe z rotate -> eg. to fly your plane or spaceship
  • Use the second stick to move your head in game or for directional thrusters. Elite dangerous has a normal and alternative flight setting so you can have both options - as needed
  • program one stick to act as a digital input -> eg simulate arrow buttons. It' s pretty cool to use the little stick under the thumb to navigate in game menus ,)

  Buttons

  Well Buttons are buttons and that's it for me and by that I mean Joystick buttons. Some of the sticks you can buy have a button included in the sticks as well.
  For me bigger buttons are better. But that depends on your taste. There are buttons with LEDs to illuminate the button when you push them and much more. So pick you poison there.
  

  Most if not all buttons are digital. If you wonder how the analog shoulder buttons on the xbox controllers work. That's done with a pretty nice concept.
  
  

  It is actually a rotary potentiometer (red brackets) attached to a nice mechanic that will rotate the pot when pressing down the button. 
  If you use your imagination and scale this concept up - bam there is your option for the paddles of your next driving stick project ;)

  Toggles/switches

  The main difference between a switch and a button is that a switch will stay in the position while a button will automatically jump back once you release it.
  Most common are On/Off switches but there are also On-On switches. I bought On-On they look like this

  On-Off switches have "2 legs" while the On-On has "3 legs". I use mine as On-Off switches by just connecting 2 off the 3 legs because the number of pins used becomes an issue very quickly. More on this in anther instructions

  The use for the switches are for me two main concepts:

  • Use them as a keyboard key press -> logically it is like a "one state change - press and release a key (the same key usually)"
    It is also possible to code it the way to act on status change -> key goes from on to off -> "M" key press and release. On to off -> "ESC" key pressed and released
    eg. enter a map and leave it...
  • As the physical representation of an IF Statement -> "If the switch is on - the little stick acts as arrow keys - else the stick acts as 'wasd' keys"

  Sliders

  Sliders are just another type of potentiometer. For the microcontroller - they work exactly the same as described in the stick.  From joystick perspective it is usually used as the Z axis or left/right slider
  I think they are best known from those huge mix tables in music studios
  
  

  But be careful, as far as I read, especially in these studio equipment - logarithmic pots seem to be preferred! 
  For a gaming device go for linear ones!

  Rotary knobs

  Those thingys
  
  

  The question you need to ask yourself on this is: 

  • Is the position of the knob meaning something -> like turn up the volume or throttle up and down
    Then this knob will have a limit amount of turns or even only some degrees angle from low to high
    => go for a rotary potentiometer -> but keep in mind analog input requires an axis which are limited in the joystick implementation in Windows!
  •  It is important to know in which direction the knob is turned -> like choose the next or the previous target in your space sim
    The knob can be turned unlimited...
    => go for a rotary encoder -> they send a digital signal so you can eg. do a key press/release when turned left/right and so on

  Rotary encoders often have a button included engaged when you press the knob. Tons of information about them in the net if you want to know how they work internally.  

  But one thing is worth to mention: They come in 2 flavors if you buy them!

  The plane rotary encoders need a support wiring with capacitors and resistors if you want to do it by the books (maybe it works without - did not try it) You end up soldering something like this... ;)
  
  
  

  In the spirit of: Why buy something cheap if you can build it for 2 times the money on your own *lol*
  

  I recommend to go with breakout boards for the encoders. They are cheap and you are on the save site with them. 
  If you want to learn something and improve your solder skills - go for the plane ones

  Displays

  Lots of options here as well. OLED ones with color - without color. Lots of sizes. But this all is not worth anything if your micro controller cannot get it working :(
  Especially the Teensy is very picky on this topic. Two main reasons:

  • Voltage for operations
  • Availability of libraries

  First thing is pretty obvious. The teensy operates only on 3 V while some controllers support only 5V or both. No clue what the Arduino Pro Micro supports
  So if you choose your display - pay attention to the voltage they can operate on. 

  The other  thing is a bit more complex. While the teensy is arduino compatible with the teensyduino addon for the Arduino IDE - some libraries are not!
  The only display controller that worked out of the box for me on the teensy is the SSD1306 with the Adafruit SSD1306 and GFX libs...
  So pay attention to the display specs here as well!
  

  Finally connection options of the display. (O)LED Displays need a huge amount of pins if you wire them natively! So go for a breakout board with a dedicated controller here as well! I used a I2C based one but I guess SPI would work as well

  Feel free to add your comments on this topic. I will gladly add additional info to this instruction if it is useful!

• 2

  The PIN problem

  Now that you have selected your components. The info in this instruction is essential before you can start to wire up things!

  A common problem for sticks with Arduinos / Teensy as controllers is the the limited number of pins the breakout boards have.

  Since I am using the teensy board I will talk about this one only.
  As you can see on the pinout https://www.pjrc.com/teensy/pinout.html the teensy 4 has 10 analog and 14 digital pins - where the analog pins can be used as digital pins as well.

  For my current setup there are:

  • 2 x 3 axis sticks and one 2 axis stick plus an analog slide potentiometer -> 9 analog inputs
  • 11 arcade buttons, 3 buttons overall on the sticks,  8 switches a rotary encoder with a button -> 23 digital pins 

  By using simple arithmetic ;-) it is easy to see that this will not work by directly wiring every input to a pin on the teensy.

  So if you do not use this many components forget about the rest of the instruction. Wire them straight to your board - no problem

  Else - there are 2 common approaches for the button problem:

  •  a button matrix
  •  a multiplexer

  The Matrix

  There are  tons of excellent articles about the button matrix and a matrix button pad is included in most Arduino starter kits - so I will not cover all the details. Basically it looks like this

  you wire the buttons in a matrix. In the above example the columns are used as outputs -> voltage supplied to them and the rows are inputs.
  The code steps through all the output pins (columns) and reads the values on the input pins. Some would call his this method multiplexing ;)

  As far as I know there are also libraries available for Arduino which to most of the magic for you with debounce and everything. For my 23 digital pins I could have used a 5 by 5 matrix -> 10 pins for 23 inputs is not to bad of a deal.

  But soldering this matrix in the actual stick seemed a bit annoying  to me... ;). So I dropped this approach.
  

  Further more there is no way to multiplex analog inputs from potentiometers - although this would not have been a a problem in my use case.

  The (hardware) multiplexer

  a good alternative for a guy with mediocre solder skills like me is a hardware multiplexer where all the wiring is happening in an IC/breakout board.  The CD74HC4067 chip was the solution for me. it looks like this:

  Its a 16 channel multiplexer (C0 to C15 in the picture).  16 decimal needs 4 bits to address (S0 to S3) and one signal pin to read the current input (SIG). This means you can read 16 inputs by utilizing 5 pins on your board.
  The code maybe a bit harder to read but the soldering is straight forward. One pin of the arcade buttons all to ground and the other one straight to the channel of the multiplexer. Where I decided to not directly solder the cables to the multiplexer - used dupont connectors to be a bit more flexible. This looked something like this in my stage 2 model

  The red square are the 2 multiplexers ( one for buttons, one for analog sticks) and all the white cables are the button inputs.

  Summary

  Do not forget to consider the "Pin Problem" in your planning.
  Choose your preferred option and plan your wiring accordingly

  As always - feedback and comments are welcome 

• 3

  Prototype wiring - Part 1: Flying wires

  After choosing your components and thinking about the "PIN Problem" it is time to take the next step forward -> build a prototype.

  Before we start: Most of the time I do not do a scientific approach. I more do an empiric approach. 
  

  • Build
  • Test and/or fail
  • rethink 
  • improve
  • repeat

  This means, most of the time I am not using any wiring plans at all and I tend to be very "pragmatic" - not to say sloppy - when setting up test setups.
  I know of tools like fritzing and similar but that's not my thing, so for now - I will not provide any fancy wiring plans. 

  But of course if you more like the scientific approach you should plan out your wiring with some software or on a piece of paper first... That said - lets start 

  I would not recommend to start with all the components together. It is better to start component by component and extend your functionality step by step. This way you will not loose the overview (that fast ;) ) and troubleshooting is much easier on a small setup. 

  Some small steps to go for test wirings may be:

  • Get your first analog stick working as a joystick
  • add some buttons to the setup
  • add the sliding pot
  • add some switches

  For the (O)Led display I would recommend a separate test setup.

  The way your first prototype may look like depends much on the equipment you have on your disposal besides your game devices components. There are some absolute essential in my humble opinion. Out of the box ( :-) ) these are:

  If you own an Arduino already - 2 of them should be pretty familiar 

  • breadboard (in the middle)
  • preconfigured cables with different dupont connectors (on the right)

  Those 2 are included in pretty much every starter kit. Not that common there are the "Crocodile Clamp" cables (on the left).
  Well at least, that is what I call them. If there is another name in english for them -> let me know. 

  The reason why they are so important is - a lot of the components will not come with any cables at all. Like arcade button, the big sticks and switches. Most of the time they are prepared to solder cables directly to them - with those little "legs"
  

  For a prototype - I at least - do not want to solder anything. Maybe you do not have a soldering iron at all, for now. So the crocodile clamps are a good workaround. If you combine them with the female-female dupont cables you are all set!

  So a real life setup to test the dual sticks looked like this:

  But be warned if you want to wire a complete prototype like this - things might get a bit messy ;)
  
  

  Seems a bit stupid - but if it's stupid and it works... :o)

  Of course all the wiring is not worth much if there is no code to support it. I will add Coding instructions later on. But if you want to start testing immediately checkout this tutorial for the teensy it has all info you need for a basic stick: https://www.pjrc.com/teensy/td_joystick.html
  

  Next instruction will be on how to build a more durable, but still flexible wiring  

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