3D printed Data Slate props

For a long while I've been using old Nexus 9 tablets to act as 'cyberdecks' in our Cyberpunk LARP, but I was recently asked to dress them for a 40K themed one this summer.

The old 3D printed cases were getting long in the tooth and were clearly just unpainted poor quality 3D prints. So I started completely from scratch for this, only re-using my CAD model of what I needed to hold the tablet securely and operate the power and volume buttons on the side.

One of the major things I wanted to get away from was the obviously rectangular shape of the tablet screen. It's a common sci-fi trope for screens to be weird shapes and to emulate this I modelled a surround with truncated corners and cutouts for the cameras and speakers.

This looks great so long as the tablet is asleep, but once it wakes up the real shape of the screen is obvious. There's only so much I can do here and while I could have covered some of the usable area Android apps tend to quite rightly assume the whole screen is accessible.

On the old tablet holders I had added some old bag carrying straps, which are very practical but untidy looking so I added a very chonky carrying handle as part of the case.

This makes the whole thing physically large, which has the added advantage of making these hard to hide or just stuff in a bag. It's a not uncommon problem in LARP that acquisitive players will squirrel something away in their bag and it's never seen again unless they want to leverage it somehow. These were to have PDFs on them that were plot-relevant and we wanted that information very clearly available.

Annoyingly there's no open source 'kiosk mode' application for Android that I could find but to make sure the PDFs were visible whenever somebody woke the tablet I used the "Librera FD" viewer and the basic screen pinning functionality in Android to keep it maximised.

When asked to make these I wasn't sure how long the documents would be so I decided to add physical controls for paging through and searching documents. There's a scroll wheel, two buttons to page up and down plus a keyboard for text entry. This re-uses an X-Box 360 chatpad as making your own small keyboard keycaps that don't look terrible is very awkward and fiddly. There's also a piezo sounder to do keyboard/button bleeps.

This section is the part I'm least pleased with: the chatpad is too small and the buttons I ordered were too long to allow me to inset it like I did with the tablet section.

The design is ugly because I was rushing and I will most likely re-do this part before they are used again. I may even go as far as making a custom keyboard using tactile switches that fills more of the area.

These physical controls are driven by ESP32-S2 dev boards acting as USB OTG HID devices. I ran into a bit of a struggle with the code for this. Every time the tablet went to sleep, it would disconnect the USB devices and refuse to reconnect. I think this is related to this reported bug but was in a hurry to get this done so just made the ESP32-S2 restart whenever the tablet went to sleep. There is a little latency on waking it up but not a great deal. I would like to add more functionality to this setup, including my LoRa mesh network messaging stuff, so I need to overcome this problem. The 'cheat' would be to connect the ESP32 over BLE but given I have a direct physical connection to the tablet this sort of offends me and I'd need to swap to an ESP32-S3.

In the end though, this all worked out well, I got four of these made in different colours so they could be told apart and the paint weathering on the main body looks good. I didn't have time to weather the control sections so they just got some scratches but if I'm going to re-do them that's fine. I may also try to make some left handed variants and some without the big handle.

These will definitely be getting a load of use. Put Termux on them and they are almost 'real computers' and while the performance is poor in modern web applications we always curate what we let our players access. I've got a drawer full of Nexus 9s so printing and painting a few more of these over the next few months will get me a nice stash of usable props.

retroTerm release 0.1.6

At our recent LARP High Frontier: The Drake Objective I used retroTerm my ANSI/VT terminal GUI widgets library to create a prop where the players interacted with an offscreen extra-terrestrial intelligence through a purposefully retro computer interface.

This is the whole reason the library got written in the first place.

Work started on retroTerm in maybe 2019. Then the game it was scheduled to be used in got postponed due to the pandemic and despite the extra time that afforded me I didn't manage to deliver anything usable for the game when it finally happened.

It was a terrible case of overpromise and underdeliver, ie. I delivered nothing usable. The work on the retroTerm library itself was fine but the messaging system it was to provide the user interface for just wasn't stable and we abandoned it at the last minute.

When a short 'midqual' LARP event came up last year I rewrote all the messaging code and produced a version of the thing with a cut-down retroTerm user interface that saw a tiny amount of use. There were still some frustrating problems though: centred on it needing an accurate timestamp for all the messages and me getting caught out by GPS just not working for this. I had not realised the building it would be used in had a metal roof and the dubious signal ended up causing it to end up with spurious date & time values, some in 2080. Which is perhaps a failing of the GPS library I used to process the NMEA sentences but regardless this was not good and caused it to misbehave.

As a result when The Drake Objective was announced I made some new hardware that included a hardware real-time-clock and did a ton of work on making damn sure the setup would have a correct time. It couldn't just connect to WiFi and get it from the Internet as it'd be used in a building in a field with no services and also very dubious 4G signal we weren't sure would be usable.

The new hardware worked around the issues well and the whole prop behaved pretty well during a weekend long game albeit in its still quite cut down form.

Part of putting this thing together saw me make some improvements to retroTerm.

I found and squashed a memory leak[1] and have just improved the way it handles 'list box' widgets so I feel it's in a pretty solid spot. Today I fiddled around testing it on an ESP32 over Classic Bluetooth Serial rather than a wired connection and this worked trivially easily.

This is something I can imagine use cases for so I'm glad I finally tried it out. Often ESP32 projects get built with little captive web portals to configure/control them but this gets 'big' quickly. Being able to run a wireless retroTerm interface for this is something I'm going to try in an upcoming project.

Anyway this was all a big ramble to say retroTerm 0.1.6 is out and seems to be working well.

Next on my list is making that multi-user peer-to-peer messaging system I originally promised back in 2019 happen. Even if we never actually use it I want to have done it and to that end have been writing great swathes of code in preparation already which I've been sticking in some new libraries. When they're more finished I'll share them.

[1] Which only showed up if constantly updating something like a clock widget

You now have fifteen minutes to reach minimum safe distance

We have just run a sci-fi LARP where we wanted to have the classic trope of a computer with a sad voice telling the players bad news like MU|TH|UR in Aliens, GERTY from Moon, HAL in 2001 etc. etc. It's a very common part of the aesthetic of a certain kind of sci-fi.

Our game was set in the Aliens universe so we wanted to emulate the female voice from MU|TH|UR. None of the GMs are voice actors (or female) so I made a text to speech device for this.

I got quite far down the rabbit hole of power saving and solar charging on a Raspberry Pi 3A+ then somebody offered to bring a massive lead-acid battery to the game for me so I abandoned worrying about all that because brute force won out. I will come back to it though as I want to make a nice portable outdoor Pi to provide 'infrastructure' at future events. Having infrastructure I can deploy easily in a field with no power has been a constant thing I've been nibbling at the edges of for years mostly with ESP32s and mesh networking.

I put the Raspberry Pi 3A+ into a waterproof box I had and powered it off that big battery all weekend. I even forgot to shut it down on Saturday night and it jut kept going.

The Raspberry Pi communicated with the Internet over 4G using a dongle I had kicking around which conveniently has a tiny NAT router in and presents as a USB ethernet so 'just works' with zero configuration on the Pi, or pretty much anything else. I'll probably try find another dongle the same, it's handy for these reasons.

I then made a 'bot' in the popular messaging app Telegram using their example Python script and used the Microsoft Azure AI voice engine to generate a very convincing voice. This was not a very sophisticated script, really just Telegram's example bot script, their recipe for restricting access to certain Telegram IDs and Microsoft's example text-to-speech script all smushed together with my rudimentary understand of Python as I'm normally an Arduino/ESP32 C++ person.

None of this needs much processing power: an original Pi could probably do it, except the Microsoft library expects a 64-bit OS so the Raspberry Pi 3A+ was a good fit. It's the lowliest, most power efficient 64-bit Pi that also has an analogue audio out and I had one in my stash of dormant SBCs.

The end result was we could type a message on our phone into a Telegram group chat and it would then ring out across the game using walkie-talkies to broadcast it over a large area. There was a little bit of impedence/level matching needed for the line out from the Pi to go into the headset input of the walkie-talkie. I used voice activation in lieu of 'push-to-talk' but that too worked great once I added a preamble 'bong' and little gap before the talking. I may go back and investigate triggering the push-to-talk through the headset connector using one of the Pi GPIOs as it's more predictable and the headset has the feature: I was just bashing the thing together quickly for the game.

"You now have fifteen minutes to reach minimum safe distance"

If players wanted to talk to MU|TH|UR they would just talk on the same walkie-talkie channel and we were listening. We had some quite long player conversations back and forth with MU|TH|UR like this and it worked brilliantly. We'll be using this setup again.

GalactiNet GT420 terminal

Back in May I was part of a team running a short LARP in our High Frontier universe.

The game plot called for the existence of a prototype communication device through which 'second contact' with an advanced extra-terrestrial species was being attempted.

In practical terms the intention was there would be a short exchange of messages between the players and these extra-terrestrials while very human chaos raged around them.

We like to do things with 'practical effects' at High Frontier and avoid whispered messages from GMs and the led me to somewhat overcomplicate the prop involved. A lot of this was because we intended to have an multi-user in-game messaging system at our previous event and I flamed out trying to deliver it in time, resulting in a big disappointment.

So this game I very much wanted to make that happen even if the actual amount of messaging would be trivial.

Every player was provided with a personal printed RFID card and inserting the card into a reader in the external unit logged them in.

The physical prop was made in two large chunks: a 'terminal' and the actual 'communicator' itself. Making these physically imposing yet still portable props was deliberate as the players would be faced with carrying them while under fire or abandoning them.

The 'terminal' is an old laptop motherboard and screen carefully fitted into a medium sized flight case with 3D printed and painted fascia. The flight case was interestingly laid out with a padded compartment on one side and I retained that for storage of a compact keyboard, mouse, cables and the power supply enabling it all to be packed down for moving.

Building this took a fair amount of iteration and improvisation. The original laptop battery pack was beyond use so I built one out of new 18650 cells with double the original capacity to ensure it would last the entire game.

Making an aged laptop bearably usable is an increasing struggle and the Raspberry Pi desktop for x86 is my go-to for this. By removing the Office software before updating you can still squeeze it onto 8GB SSDs and so long as you don't want to use Chrome with super-bloated sites performance is as zippy as it can be.

All it needed to do was run PuTTY as like my previous work on off-grid multi-user messaging this was a 'microcontroller first' design, implemented on ESP32-S2.

I took my previous, frankly unmanageable, project for messaging and created a new back end for it this time based around the port of sqlite available for ESP32. My goals were far more modest than the original project in UI terms but the back end still has most of the features to now resurrect it in what I hope is an actually manageable fashion.

Inside the communicator itself is a custom PCB I made a small batch for as long term I want to develop and use this messaging system for future games. It uses the ubiquitous MRC522 RFID reader and has a GPS attached for getting an accurate time signal, which is necessary for the system to work. There's also a uSD socket for storage (although it could use LittleFS), a sounder and some indicator LEDs.

By the time I was actually coding things for the game I realised I'd made some omissions on the PCBs but broadly they worked.

While the players interacted using a retroterm UI on the physical terminal, GMs could connect over WiFi and use a hacked together web interface to view previous messages and send new ones.

I did start by writing a fully featured web interface but the framework I used meant the ESP32 began to run out of memory once there was a non-trivial number of things in the database. Moving things into PSRAM helped, but not enough realistically.

The sqlite cache also caused me grief as it would rapidly eat all the heap memory of the ESP32, despite nominally being able to manage that itself. Tweaking compile time constants helped but in the end I found I had to aggressively clear the cache using the sqlite API after every interaction. By this point I was very close to the game, stressed about the deadline again and as messy as this solution was it worked well.

Using GPS for time, even indoors, worked well in testing but was another cause of stress on the day even though we're nominally an outdoor LARP system.

A cold GPS start, metal roof on the building used and need for it to work quickly ended up with us having to leave the communicator outside the building on a long USB lead for it to work at all.

I will not wholly rely on GPS for time again and look to fit a dedicated RTC that is set then updated by the GPS only if necessary. Even outdoors the time signal seemed unreliable but it was impossible for me to troubleshoot at the game. This meant weird slow performance and trouble logging on that I simply hadn't seen in testing.

In the end though, messages were exchanged and this massively overcomplicated setup delivered even though it gave me and the rest of the game team huge amounts of stress.

What I need to do now is work on it in the in-between times so that the back end approaches plug and play for other applications and my 'microcontroller first' plan actually means it can be used across a range of lightweight devices.

There was a whole PC doing almost nothing in this setup that could have done the messaging instead but my plan is this 'backwards' approach would allow cheap ESP32-based props to interact with the system.

You can buy something that could in principle be turned into a pocket touchscreen communicator for <£10 and I plan to pick up a couple. It's just the tip of the iceberg of what you can do with little ESP32 based gadgets. Previously I was thinking to use M5Stack/M5Paper products as well.

The messaging back end I've christened backslang and is on GitHub but I would say it is very much an unfinished mess not fit for anybody else to use. Maybe I'll find time to fix this before our next event. I'd love other people to dive in to the repo and fix my naïve mistakes but it seems unlikely anybody will have the inclination and time.

LARPCon 2023 interview

 I was at LARPCon 2023 with some of my old props that make good table pieces and got interviewed by LARPBook. There's a small amount of cringe in my off the cuff talk but broadly it's OK.

An open source prop: Part 1

After going to Alone: Discord LARP I ended up chatting with the organisers on social media. They had some 'hackable locks' in the game that worked OK but were really just touching a couple of pads with a wire to make a beep and change an LED.

There were several game organisers playing and chat turned to making a generic 'hackable lock' for modern/sci-fi LARPs. It's something lots of LARPs will have needed or reinvented over the years. We might use them ourselves in March.

So I'm now smashing away at code for a generic lock prop based around the old favourite of an RC522 RFID reader, WeMOS D1 mini, LEDs and a piezo sounder.

The plan is to totally open source everything, with a build guide, 3D printed case, software that is pretty flexible and can be tweaked to behave in different ways.

This has already spawned two Arduino libraries. A tap code library for taking input codes on a single button (for hacking/admin) and an RFID authorisation library. The big plan is for a Web Portal interface, probably using ESPUI again.

Churning out some libraries means the main chunk of code for the prop is much less spaghetti-like and the libraries should be eminently re-usable. I really need to do this with lots of other things I've made or started to make.

Oh and obviously the Cyberdeck prop is on hold again, with no game to use it at for a while.

Mixing my ESP-Now mesh, ESPUI and physical objects in a LARP experience

As I've mentioned before, all the stuff I work on tends to be to make props for Live Action Role Playing (LARP) events. LARP comes in many flavours but the variant I'm involved in has people solving problems and fighting skirmishes with Lasertag weapons as part of a collaborative story, usually with a science fiction element.

With the arrival of the pandemic, almost all LARP except that which was conducted via video chat went on hiatus, including a game we'd been planning for a couple of years.

However things kicked off again for us on the weekend of 3-5 September 2021 with an 'anthology event' that consisted of several short games. After a chat with one of the game organisers I agreed to set up some stuff to round their Cyberpunk themed game out.

We play on exclusively outdoor sites, almost always with no access to mains power or permanent Internet service so everything needs to be self-sufficient for the duration of the game. Also with only a couple of hours of setup time available it needed to go out quick and dirty right beforehand.

I put together several elements that got included in the game, spread across three different locations on the site.