A lot happened since my last update on the simpit – under it’s hood. Function wise it changed not so much so the older demonstration video is still better for a quick demo. I still assembled a new video from clips of the first evening with the new hardware:

Quick trip from Armstrong Orbital over to the huge crater on HIP 117029-4 and back

So what changed? I got rid of the CY-822A USB joystick controller that, while good, was also limiting. Especially in inputs and how they would react. The Raspberry Pi, that I used to drive the status indicators, is also gone. This is all replaced by one single Arduino Mega that is connected via serial over USB.

A custom joystick daemon written in Rust is listening for data from the and feeds back the flags of Elite Dangerous to drive the blinken lights. I also extended the source to add me some rotary encoders (with push button function) and I’m very happy with the result of this. That makes a whopping amount of 48 buttons and 6 axis (where 2 axis make one hat). And it feels _so good_ to have e.g. self destruct or eject cargo save under a protective cover now 😀

The panel also got an external PSU with enough ampere to drive as many LED as I may imagine so I no longer abuse a phone charger for that or risk frying of the PCB / USB.

With all that in place I streamlined my pre-flight check-list quite a lot because way less hardware is involved and most of this is automated by now. It wasn’t all fun n giggles tho and while the new hard- and software “just worked” in e.g. it was that gave me a hard time to actually use most of the new buttons.

Getting all the precious buttons into Elite as well (okay, limited to 32 thanks to an old dinput library but who is counting at this point – will simply set the rest to keyboard macros instead)

Turns out it had no idea about the device and model identifiers reported by the joystick daemon and that the kernel assumed a gamepad based on declaring e.g. ButtonNorth via the more recent xinput system really didn’t help – because that limited the amount of read buttons via xinput severe! In the end I set it’s identifier to a “vJoy” device. That I found in the DeviceMappings.xml of Elite and since this could be basically anything I gave it a try (and removed all “offending” magic gamepad buttons from the code) and sure enough Elite started accepting the inputs as expected and from there it was smooth sailing – got even the hat working.

Oh and for everyone who is wondering what exactly they are seeing on the “MFD” when I’m playing Elite: That’s basically a Website using the FUI framework. Find a quick demo video here. Without the cardboard covering up parts of the screen it looks basically like this:

I also started doodles for a version 2 – now that I have an idea what I really want.

Plans for another based on a Valkyrie Cockpit

My Primary Buffer Panel is almost completely revamped 😄 Just an now, no more in the mix. The CY-822A is also gone. I did add an external PSU to drive as many LED as I can imagine too 😄

I also programmed support for 4 to 8 rotary encoders and there is an additional slide potentiometer sitting on my desk. I still have to find space for that – but I want that very badly since I know how mining in works 🙂 That makes now 49 buttons and 4 axes so far 🙃

A more detailed write-up is planned, as usual.

You probably heard about this before: An Arduino can be made into an excellent DIY joystick. Most examples use a Leonardo or Micro for this for a very good reason. They one comes basically with a chip that is recognized as HID (Human Interface Device) hardware on any modern operating system.

This is not the case with a Mega. This one has other perks but HID it is not. It sure shows up as USB device and a ttyUSB is raised where serial communications with the Arduino can be initiated. I’m also aware that some flash the built in programmer of the Mega so it starts operating like the others (which obviously removed the built in programmer). I’m on Linux PC though so I thought it’s basically a job of tricking the system into recognizing it as joystick and call it a day and OMG was I wrong!

How it’s not done

My train of thoughts was like this: Linux still supports plenty of old serial joysticks so how complicated can it be to send some bits an existing driver recognizes. Old hardware like this is usually glued to the driver with the tool inputattach of the Linux Console Project. This does basically initialise a joystick on some serial connection and sends it off to a fitting kernel driver. This way even non-USB, or let’s better say non-HID hardware, is mapped to a kernel driver who in return will set-up the joystick subsystem and manage the communication with the stick via a serial connection.

Turns out I’m not the first one with that idea and apparently someone made it work by connecting old Playstation Controller and a Wii Classic Controller to an Ardunio and fake a Stinger device without the use of HID so Kudos to Jarno Lehtinen here and his Linux-Arduino-Serial-Joystick repo – you sure did sent me down a rabbit hole of horror and amazement. I couldn’t even get inputattach to wait for that magic string to be sent with anything else than 9600 baud and aligned stars! I also had to throw socat into this horrible mix because the Arduino would insist on rebooting on init so a timeout was guaranteed! In case you wonder how I did this:

socat -r left.raw -R right.raw pipe:/dev/ttyUSB0 PTY,link=/dev/ttyUSB1,rawer
# and xdd to show me the debug juice
tail -f left.raw | xxd -c4
# and on yet another terminal
inputattach --baud 9600 --stinger /dev/ttyUSB1

This also meant that I had to tear everything down for reprogramming the Arduino. Anyway, in the end I could finally get through that init phase where the stinger related code in inputattach is waiting for the magic key after sending “ E5E5” to finally load the Stinger kernel driver – communication for both ways confirmed!

    // "\r\n0600520058C272";
    byte byteResponse[] = {0x0D, 0x0A, 0x30, 0x36, 0x30, 0x30, 0x35, 0x32, 0x30, 0x30, 0x35, 0x38, 0x43, 0x32, 0x37, 0x32};
    if (Serial.availableForWrite() >= sizeof(byteResponse))
      Serial.write(byteResponse, sizeof(byteResponse));

At this point I had a pipe to prevent the timeout due to the resetting Arduino, the _only_ working baud rate 9600 I could figure out with the Mega, a loaded driver that was recognized as joystick and was sitting put and did… absolutely nothing. Null. Nada. Not a single bit made it to the driver and I could not figure out why. My guess is it needs a change in the baud rate to the original 1200 (?) of the Stinger but I have no idea if this is true. I could also not find any way how the stream is controlled and since the driver would fill up 2 bytes all the time and interpret them there is a fair chance that it would simply be one byte off all the time. Speculations tho, I simply didn’t grasp the stinger.c source so this is all just a theory. I do not want to admit how much time I sunk into this and I was pretty frustrated at this point. Reading some stupid serial? Not like this! Too many hoops!

So I threw it all in the bin 🚮

How it’s probably done

Say hi to /dev/uinput where you can basically raise virtual devices, like a joystick, without [much?] pain. I’m not the first one, of course, and funny enough the reason behind is very similar to mine. Read more on Virtual joystick on Linux by Gwilym Kuiper where this is all explained in great detail. The referred code at https://github.com/gwilymk/arduino-joystick sure did help me to get started and even without having touched Rust ever before I was able to quickly adjust this for my needs, doubling the possible buttons and get it up and running in just a few hours for my Linux PC. Cheers mate (also Jarno Lehtinen – you teached me a lot that day :D) 🕹️

So here it is: A Mega acting as joystick without HID over a serial connection driven by a userspace daemon (means no kernel driver required) written in Rust providing a virtual uinput device for a joystick on the “modern” event system. Heck it’s even recognized in Wine!

What a journey to begin with. Now I need a back-channel for my blinky lights so I get my Raspberry Pi back from simpit duty 🙃