# Using the TRRS Trinkey as an Assistive Technology Device
## Introduction
Giving a disabled person the ability to use a mouse and keyboard on a PC is one of the most important pieces of assistive technology we can create. Many disabled people use pushbuttons or other devices known as an AT Switch. These devices have a 3.5 mm mono jack on the end. One of the easiest ways to connect multiple switches to an assistive technology device is using the TRRS plug and jack. This gives us four conductors that we can connect to the microcontroller. In this circumstance, we have three buttons plus a common ground.
The TRRS Trinkey was specifically designed with assistive technology devices in mind. You can easily connect from 1 to 3 AT Switches to the device and use it for a variety of purposes. The great thing about this board is that it also has a STEMMA QT connector that allows us to connect other devices to the board. In this tutorial, we will connect a small OLED display that can be used as a virtual keyboard and mouse display. Using the AT Switches, a user can navigate a cursor around the display and type on a virtual keyboard. They can also move the mouse in any of eight directions, click any of the three mouse buttons, and operate the scroll wheel.
The TRRS Trinkey can also be connected to a phone or tablet with an OTG adapter to allow switch control access to touchscreen devices on iOS and many Android devices. The original learning guide for the TRRS Trinkey has a simplified switch control application in both Circuit Python and Arduino versions. However, here we will present an advanced version of the application for Arduino that allows you to use multiple simultaneous keypresses to get even more capability out of the device.
# Using the TRRS Trinkey as an Assistive Technology Device
## Parts List
One of the advantages of the TRRS Trinkey is that no soldering is required to connect the device to the display or to the AT Switches. Everything simply plugs together. We have included STL files for a 3D-printed case for the Keyboard and Mouse Emulator.
Featured
### Adafruit TRRS Trinkey - USB Key for Assistive Technology
[Adafruit TRRS Trinkey - USB Key for Assistive Technology](https://www.adafruit.com/product/5954)
It's half USB Key, half TRRS breakout_... _it's the **Adafruit TRRS Trinkey** specifically designed for Assistive Technology hackers and creators as a simple and low cost, but also flexible and extendable AT device.
Many AT interface...
In Stock
[Buy Now](https://www.adafruit.com/product/5954)
[Related Guides to the Product](https://learn.adafruit.com/products/5954/guides)
Featured
### Monochrome 1.3" 128x64 OLED graphic display - STEMMA QT / Qwiic
[Monochrome 1.3" 128x64 OLED graphic display - STEMMA QT / Qwiic](https://www.adafruit.com/product/938)
These displays are small, only about 1.3" diagonal, but very readable due to the high contrast of an OLED display. This display is made of 128x64 individual white OLED pixels, each one is turned on or off by the controller chip. Because the display makes its own light, no backlight is...
In Stock
[Buy Now](https://www.adafruit.com/product/938)
[Related Guides to the Product](https://learn.adafruit.com/products/938/guides)
Featured
### STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long
[STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long](https://www.adafruit.com/product/4399)
This 4-wire cable is 50mm / 1.9" long and fitted with JST SH female 4-pin connectors on both ends. Compared with the chunkier JST PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
In Stock
[Buy Now](https://www.adafruit.com/product/4399)
[Related Guides to the Product](https://learn.adafruit.com/products/4399/guides)
If you are only using the device for switch control, you do not need the display. You will want to add this case for the board.
Featured
### Snap-on Enclosure for Adafruit TRRS Trinkey
[Snap-on Enclosure for Adafruit TRRS Trinkey](https://www.adafruit.com/product/5981)
Here is a cute and minimal enclosure for your [TRRS Trinkey](http://www.adafruit.com/product/5954) to keep it safe during use and transport. This case has been custom designed and 3D printed to accommodate the reset button and STEMMA QT connector. No screws or glue are...
In Stock
[Buy Now](https://www.adafruit.com/product/5981)
[Related Guides to the Product](https://learn.adafruit.com/products/5981/guides)
To secure the display board in the enclosure, you can fasten it with M2.5 plastic screws or snap it onto some alignment pins and secure it with a drop of glue. Adafruit sells a nice little box such screws which are handy for this and many other projects.
Featured
### White Nylon Machine Screw and Stand-off Set – M2.5 Thread
[White Nylon Machine Screw and Stand-off Set – M2.5 Thread](https://www.adafruit.com/product/3658)
Totaling 420 pieces, this **White Nylon M2.5 Screw Set** is a must-have smörgåsbord for your workstation. You'll have more than enough screws, nuts, and hex standoffs to construct your maker projects for days on end! M2.5 screws fit nearly...
In Stock
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[Related Guides to the Product](https://learn.adafruit.com/products/3658/guides)
Most Trinkey boards sold by Adafruit are intended to be plugged directly into a PC, laptop, or USB hub. If you're using this device for switch control, you will have no problem plugging directly into such receptacles. However, it is unlikely you could see the display board from that location. So if you're using a Keyboard and Mouse Emulator with a display, you will need a USB extender cable similar to [this one from Amazon](https://www.amazon.com/AmazonBasics-Extension-Cable-Male-Female/dp/B00NH13Q8W?th=1) which has a USB A female connector on one end and a USB A male connector on the other end.
## AT Switches
Assistive Technology Switches have a 3.5 mm Mono plug on them. They can be obtained from a variety of sources. If you aren't sure what kind of switch works for your disability, we recommend the ["Adaptive Gaming Kit" from Logitech](https://www.logitechg.com/en-us/products/gamepads/adaptive-gaming-kit-for-access-controller.943-001253.html). It contains an assortment of switches of various kinds that you can try out.
The TRRS system is traditionally used for stereo headphones plus a microphone channel. If you are using more than one switch you will need some sort of splitter to separate the three channels.
If you only use one switch, it can be plugged directly into the TRRS Trinkey jack. Note that the keyboard & mouse emulator requires at least 2 switches however Switch Control can be used single switch.
If you are using 2 switches you will need a splitter that brings out the left and right headphone channels.
If you require all 3 switches (which is ideal) you will need one adapter that splits out the microphone channel from the headphone channel and then another adapter that splits the headphones into the left and right channels. Unfortunately, we have not found a commercially made adapter that splits out all three channels. We have built custom adapters that do so but that requires soldering skills.
Here are 2 commercially available splitters that separate the microphone channel from the headphones.
[2 Pack Dual 3.5mm Jack Splitter, Headphone and Mic, TRRS 4 Pins from Amazon](https://www.amazon.com/dp/B09K82GN4Q?th=1)
The black one on the left splits the headphones from the microphone. The right one on the right does not do anything useful for us. It simply duplicates the headphone jacks but does not split out the left from the right channel.
Here is a similar device.
[MillSO Headphone Mic Splitter from Amazon](https://www.amazon.com/dp/B071DMCZQF?th=1)
The green jack is the headphone jack which will have to be split and a pink one is the microphone jack that can be used directly.
Here is an example of a splitter that converts stereo headphone channels into individual left and right channels. It can be used for a 2-switch application or in conjunction with the previous devices for a 3-switch application.
[3.5mm Stereo to Dual Mono Cable from Amazon](https://www.amazon.com/dp/B096XNHTH3?th=1)
Here are photos of how to use these devices in combination to break out 3 Mono switches from a TRRS jack.
Here is a 2 switch application
If you want to mount the case for the Keyboard and Mouse Emulator you will need a 1/4"-20 hex nut available from any hardware store or [this one from Fastenal](https://www.fastenal.com/product/details/70710).
# Using the TRRS Trinkey as an Assistive Technology Device
## Mouse and Keyboard Emulator
This learning guide contains two projects. One of them is a mouse and keyboard emulator that makes use of an OLED display. The TRRS Trinkey is connected to the display using a STEMMA QT jumper cable. You then plug it into your device using a USB extension cable.
You navigate symbols on the screen using 2 or 3 AT switches and select the function you want to use.
We have provided Fusion 360 and STL files for a 3d printed case.
# Using the TRRS Trinkey as an Assistive Technology Device
## Assembly of Mouse and KB Emulator
We have provided Fusion 360 and STL files for 3D printing a case for the Mouse and Keyboard Emulator. They are available in our [GitHub repository for this project here.](https://github.com/cyborg5/TRRS-Trinkey-Mouse-and-Keyboard-Emulator)
There is a base piece to the case complete with a receptacle for a 1/4"-20 Nut which can be used to mount the device for easy viewing. There are two versions of the lid. One has 2 alignment pins and 2 screw holes which can take M2.5 screws to hold the display module in place. The other version has 4 alignment pins and you can secure the display with a drop of glue. The pieces of the case snap fit and no glue or fasteners are required.
The video below illustrates how to assemble all of the parts.
https://www.youtube.com/watch?v=TZm09c346Aw
Briefly, the steps are as follows…
3D print the case.
Connect the display board and the Trinkey together using a STEMMA QT cable. On the Trinkey board it is the white connector on top of the board. On the display board you can use either side. We use the one on the right when looking at the backside of the board.
Secure the display board into the lid of the case. Use M2.5 screws and nuts or use the version of the lid with pins only and put a drop of glue over each pin. We recommend hot glue because it can be scraped off if for some reason you ever need to disassemble the case.
Insert the 1/4"-20 nut in the base of the case and secure it with glue or tape.
Insert the Trinkey board into the base of the case with the USB A connector extending outward and the TRRS Jack aligned in the provided hole.
Snap the case together making sure that the wires are not being pinched. It is a snap fit with a latch at the top and bottom of the case.
Connect a USB extender cable to the USB connector and attach your switches to the device using the TRRS Jack. Details on the kinds of switches and adapters you may need are in the Parts List page of this tutorial.
# Using the TRRS Trinkey as an Assistive Technology Device
## Software for Mouse and KB Emulator
You can obtain the software for the Mouse and Keyboard Emulator with Display from the [GitHub repository for this project which you can find here.](https://github.com/cyborg5/TRRS-Trinkey-Mouse-and-Keyboard-Emulator)
The software for this project is only available for the Arduino IDE and is not available in Circuit Python. For details on how to upload software to this board using the Arduino IDE see [this section of the learning guide for the TRRS Trinkey.](https://learn.adafruit.com/adafruit-trrs-trinkey/setup)
The sketch that you want is in the `code/TRRS_KB_Mouse` folder of the GitHub repository.
Connect the board to your computer via USB and upload the sketch.
The display will show the simulated keyboard that looks like this.
We presume you're using three AT switches. One moves the cursor to the right. Another to the left and the third button selects.
You can adjust which button performs which function. In the Arduino IDE, click on the tab labeled "`my_inputs.h`". At approximately line 22 you will find the following code:
```cpp
//GPIO pin numbers for pushbuttons. Rearrange these to suit your application
#define PREVIOUS PIN_TIP
#define SELECT PIN_RING1
#define NEXT PIN_RING2
```
This is configured with the left AT switch called PREVIOUS connected to the TIP of the TRRS Jack, the SELECT switch is connected to RING1, and the right AT switch called NEXT is connected to RING 2. You can edit these to suit your taste. After editing, save the file and re-upload the software.
See the next page for details on how to operate the device.
# Using the TRRS Trinkey as an Assistive Technology Device
## How to Operate the Mouse and Keyboard Emulator
Here is a YouTube video demonstrating all of the functions of the device. Below that, we have a summary of what's in the video.
https://www.youtube.com/watch?v=TZm09c346Aw
When you initially upload the sketch, you will see the keyboard screen shown above. This is one of three screens available. You navigate the cursor around the screen using your LEFT and RIGHT AT switches and then select the key you want to press using the SELECT switch. If you only have 2 switches use one of the switches to navigate horizontally and when you get to the end of the row it will wrap around to the beginning.
If you simultaneously press the RIGHT and the SELECT switch, the cursor will move down. If you simultaneously press the LEFT and the SELECT switch, the cursor will move up.
For users who cannot press two switches simultaneously, when you get to the right and of the row go one step further to the right, the cursor will convert to a down arrow symbol. If you press SELECT the cursor moves down one row. If you go one additional step further to the right the cursor changes to an up arrow symbol and pressing SELECT moves the cursor up one row. An additional step to the right wraps around the beginning of the row.
The top row consisting of "KMA" is used to navigate between three display pages for keyboard, mouse, and arrows respectively.
The first row of the keyboard screen consists of numbers as on a standard keyboard. The symbol on the far right is a BACKSPACE key. On the next row the symbol on the far right that looks like a stylized "X" is the delete key. The last two symbols on the third row are the ENTER and SPACE BAR keys.
The last four symbols of the fourth row are toggles for SHIFT, CONTROL, ALT, and GUI. The GUI key is the Windows Key on Windows systems and the Command Key on Mac computers. When you press a toggle, an indicator will appear on the right edge of the screen. These toggle on and remain on until you press them again. Also, the "0" below the "S" SHIFT toggle will turn off all toggles.
The fifth row consists of arrow keys left to right they are: HOME, UP, PAGE UP, LEFT, ENTER, RIGHT, END, DOWN, and PAGE DOWN. This is followed by a lowercase "g" which is a non-toggled version of the GUI key. We already explained that the "0" releases all toggles. The next two symbols are ESCAPE and PRINT SCREEN. The bottom row is function keys F1 through F12.
When using the SHIFT toggle, the device has to completely redraw the screen to show the appliqués characters and punctuation symbols used in shift mode. This can take a couple of seconds. the shift screen is shown below.
To perform mouse movement commands, go to the top row and select the "M". The screen will then redisplay as follows.
The top row consists mostly of mouse direction arrows. Left to right these symbols are: UPPER LEFT, UP, UPPER RIGHT, LEFT. The lowercase "l" single clicks the left mouse button. This is followed by direction symbols for RIGHT, LOWER LEFT, DOWN, and LOWER RIGHT. The lowercase "r" is a single right click of the mouse. The "0" is used to clear all mouse toggles.
The second row begins with three mouse toggle keys. The uppercase "L" presses and holds the left mouse button. The uppercase "R" presses and holds the right mouse button and "M" presses and holds the middle mouse button. This is followed by a lowercase "m" which single clicks the middle mouse button. The "w" and "W" scrolls the mouse wheel down and up respectively. The "SCA" symbols are toggles for SHIFT, CONTROL, and ALT respectively. This allows you to do things such as "SHIFT LEFT CLICK" for example. Note: the "0" at the end of the first row releases not only the mouse toggles but the keyboard toggles as well.
By default, each time you press one of the arrow keys, the mouse moves 10 units in that direction. You can adjust the speed of the mouse using the "f" and "s" commands at the end of the last row. Repeatedly clicking them makes the mouse go faster or slower. Here is what the screen looks like when adjusting mouse speed.
The third screen available is for arrows and other special functions. You select it using the "A" command on the top row. It displays a screen that looks like this.
The top row consists of arrow commands. They are available on the keyboard screen as well but sometimes it's handy to have them on a separate screen. The top row functions are: HOME, UP, PAGE UP, LEFT, ENTER, RIGHT, END, DOWN, PAGE DOWN, and SPACE BAR.
The second row contains some special functions that are useful for cutting and pasting. Although that first symbol looks like a "z" it actually presses "CONTROL-Z" which in many programs is interpreted as UNDO. The "yxcv" are also automatically control keys which in most programs are interpreted as REDO, CUT, COPY, and PASTE.
This is followed by ESCAPE, BACKSPACE, INSERT, DELETE, and TAB.
The bottom row starts out with our typical toggle keys for SHIFT, CONTROL, ALT, and GUI. The "g" is a non-toggled GUI. The "0" releases all toggles.
This is followed by three more special functions. This "t" produces an ALT-T which switches between open windows. The final two symbols are GUI-LEFT\_ARROW, and GUI-RIGHT\_ARROW which on Windows computers will dock the current window to the edge of the screen.
See the YouTube video at the top of the page for a demonstration of all of these functions.
Look at the code in the file `code/TRRS_KB_Mouse/my_pages.h` to see the definitions of all three of these screens. You can add your own custom commands. We won't go into the details here but the code is well commented and you should be able to figure it out.
# Using the TRRS Trinkey as an Assistive Technology Device
## Advanced Switch Control
[The primary learning guide for the TRRS Trinkey found here](https://learn.adafruit.com/adafruit-trrs-trinkey) contains a simple sketch both in Arduino and Circuit Python for using the device for switch control access to iOS and some Android devices. Note: Not all Android devices have Switch Control capabilities. Here we will provide an advanced Arduino sketch that allows you to use multiple simultaneous keypresses to add even more functionality. We also demonstrate the use of long and short presses for additional features.
You do not need a display for this application–just the TRRS Trinkey and from 1 to 3 AT Switches. Although you can do switch control with just 1 switch, this tutorial presumes you have at least 2 and preferably 3. Again these switches would be designated LEFT, RIGHT, and SELECT.
You will need an OTG adapter to connect the Trinkey to your iOS or Android device. The software emulates a keyboard and sends keystrokes to your touchscreen device which are interpreted as switch control commands.
Begin by connecting your Trinkey to a computer and upload the sketch found at `code/TRRS_Switch_Control` which can be found in the [GitHub repository for this project.](https://github.com/cyborg5/TRRS-Trinkey-Mouse-and-Keyboard-Emulator)After you have uploaded the sketch, call up a notepad or word processing application on your computer and select it with your mouse. Then test if the Trinkey is working properly. It should send keystrokes when you press your AT switches.
The LEFT switch will send "l", RIGHT sends "r", and SELECT will send "s". Simultaneously RIGHT and SELECT should send "d" and simultaneously pressing LEFT and SELECT should send "u".
You can modify which switch performs which function by editing the code in `code/TRRS_Switch_Control/my_inputs.h` at approximately line 23 which currently reads as follows:
```cpp
//GPIO pin numbers for pushbuttons. Rearrange these to suit your application
#define PREVIOUS PIN_TIP
#define SELECT PIN_RING1
#define NEXT PIN_RING2
```
The left cursor button called PREVIOUS is connected to the TIP of the TRRS Jack, the SELECT is connected to RING1, and the right cursor button called NEXT is connected to RING 2. You can edit these to suit your taste. After editing, save the file and re-upload the software.
Once you have verified that it works, disconnect the Trinkey from your PC and connect it to your touchscreen demise using your OTG adapter. You can call up a notepad application on your device and test the buttons one more time. Then configure your device for switch control. The YouTube video below gives detailed explanations of how to set up switch control on an iOS device in our case an iPad mini. The process is the same for other iPads or iPhones. We do not have access to Android devices to demonstrate that but there should be tutorials available elsewhere.
https://www.youtube.com/watch?v=pN91OfULG8c
# Using the TRRS Trinkey as an Assistive Technology Device
## Links and Downloads
Here are links of interest and downloads related to this guide:
- [Primary Learning Guide for the TRRS Trinkey](https://learn.adafruit.com/adafruit-trrs-trinkey)
- [GitHub Repository containing code and 3D printing models for the case.](https://github.com/cyborg5/TRRS-Trinkey-Mouse-and-Keyboard-Emulator)
- YouTube video "[Assembling the TRRS Trinkey Mouse and Keyboard Emulator](https://www.youtube.com/watch?v=TZm09c346Aw)"
- YouTube video "[Demonstrating the TRRS Mouse and Keyboard Emulator](https://www.youtube.com/watch?v=EnViZDao30E)"
- YouTube video "[Configuring iOS Switch Control Using the TRRS Trinkey](https://www.youtube.com/watch?v=pN91OfULG8c)"
For further assistance with this and other assistive technology projects visit AT Makers on Facebook at [https://www.facebook.com/groups/ATMakers](https://www.facebook.com/groups/ATMakers) or [https://atmakers.org/](https://atmakers.org/).
## Guide Products
### Adafruit TRRS Trinkey - USB Key for Assistive Technology
[Adafruit TRRS Trinkey - USB Key for Assistive Technology](https://www.adafruit.com/product/5954)
It's half USB Key, half TRRS breakout_... _it's the **Adafruit TRRS Trinkey** specifically designed for Assistive Technology hackers and creators as a simple and low cost, but also flexible and extendable AT device.
Many AT interface...
In Stock
[Buy Now](https://www.adafruit.com/product/5954)
[Related Guides to the Product](https://learn.adafruit.com/products/5954/guides)
### Monochrome 1.3" 128x64 OLED graphic display - STEMMA QT / Qwiic
[Monochrome 1.3" 128x64 OLED graphic display - STEMMA QT / Qwiic](https://www.adafruit.com/product/938)
These displays are small, only about 1.3" diagonal, but very readable due to the high contrast of an OLED display. This display is made of 128x64 individual white OLED pixels, each one is turned on or off by the controller chip. Because the display makes its own light, no backlight is...
In Stock
[Buy Now](https://www.adafruit.com/product/938)
[Related Guides to the Product](https://learn.adafruit.com/products/938/guides)
### STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long
[STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long](https://www.adafruit.com/product/4399)
This 4-wire cable is 50mm / 1.9" long and fitted with JST SH female 4-pin connectors on both ends. Compared with the chunkier JST PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
In Stock
[Buy Now](https://www.adafruit.com/product/4399)
[Related Guides to the Product](https://learn.adafruit.com/products/4399/guides)
### Snap-on Enclosure for Adafruit TRRS Trinkey
[Snap-on Enclosure for Adafruit TRRS Trinkey](https://www.adafruit.com/product/5981)
Here is a cute and minimal enclosure for your [TRRS Trinkey](http://www.adafruit.com/product/5954) to keep it safe during use and transport. This case has been custom designed and 3D printed to accommodate the reset button and STEMMA QT connector. No screws or glue are...
In Stock
[Buy Now](https://www.adafruit.com/product/5981)
[Related Guides to the Product](https://learn.adafruit.com/products/5981/guides)
### White Nylon Machine Screw and Stand-off Set – M2.5 Thread
[White Nylon Machine Screw and Stand-off Set – M2.5 Thread](https://www.adafruit.com/product/3658)
Totaling 420 pieces, this **White Nylon M2.5 Screw Set** is a must-have smörgåsbord for your workstation. You'll have more than enough screws, nuts, and hex standoffs to construct your maker projects for days on end! M2.5 screws fit nearly...
In Stock
[Buy Now](https://www.adafruit.com/product/3658)
[Related Guides to the Product](https://learn.adafruit.com/products/3658/guides)
## Related Guides
- [Adafruit TRRS Trinkey](https://learn.adafruit.com/adafruit-trrs-trinkey.md)
- [Monitor Your Greenhouse with a No-Code Environmental Sensor](https://learn.adafruit.com/monitor-your-greenhouse-with-a-no-code-environmental-sensor.md)
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- [Tightrope Unicycle Bot](https://learn.adafruit.com/tightrope-unicycle-bot.md)
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- [Guitar Synth with CircuitPython SynthIO](https://learn.adafruit.com/guitar-synth-with-circuitpython-synthio.md)
- [Desk Calculator with CircuitPython](https://learn.adafruit.com/desk-calculator-with-circuitpython.md)
- [Tiny Pod - BLE Rotary Encoder for iWatch](https://learn.adafruit.com/ano-pod.md)
- [reef-pi Guide 6: pH Monitoring](https://learn.adafruit.com/reef-pi-guide-7-ph-monitoring.md)
- [Cyber Cat MIDI Keyboard](https://learn.adafruit.com/midi-cyber-cat-keyboard.md)
- [Adafruit Fruit Jam](https://learn.adafruit.com/adafruit-fruit-jam.md)
- [CompuCanvas 101 - Transitions](https://learn.adafruit.com/compucanvas-101.md)
- [Adafruit Feather RP2040 Adalogger](https://learn.adafruit.com/adafruit-feather-rp2040-adalogger.md)
- [Adafruit Metro M7 1011 with AirLift](https://learn.adafruit.com/adafruit-metro-m7-with-airlift.md)
- [CircuitPython Libraries on any Computer with FT232H](https://learn.adafruit.com/circuitpython-on-any-computer-with-ft232h.md)