Print over Bluetooth using an ESP-32

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Not bad for around twenty pounds

The thermal printer I ordered a while back has arrived. I’ve been playing around with it. What I want to do is control the printer over Bluetooth from an ESP-32 device. Then I can see about getting an ESP-32 with a camera and getting pictures off that and into the printer. First thing I did was fire up BLE Scanner for the iphone and take a look at the services provided by the device. I used this to send some ASCII codes to services I thought might work (you can do this with the program - it’s great fun) and managed to get the printer to print out “hello”. Which was nice.

Then I went to the source code for my Furby Bluetooth connection program and modified it to use the services that the printer supports and managed to make that print “hello” too.

Then, as I was rolling up my sleeves to start building the printer control software it dawned on me that someone else might have done this before. And someone has. He’s called Larry Bank and you can find his splendid library here. I had to make one tiny change to his code. My printer has the name “MPT-II”, which was not on the list of the printers supported by the driver. I fixed this (in a way that I’m not particularly proud of) by editing the file Thermal_Printer.cpp in the src folder for the library installation and changing the first printer name in the list to MP-II. It was on line 59 of the file in the version I was using.

const char *szBLENames[] = {(char *)"MPT-II",

It works a treat. The library is very comprehensive. It can do different sized text, barcodes and even print images. The next thing to for me do is to get an ESP-32 device with a camera and discover how to get images off it. However, if you have Arduino app which you just want to use with a printer this is a very self-contained, cheap and portable way to do it.

How to write a technical book

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So, I’m loitering on this forum and Tamás was asking if anyone had any tips for first time technical writers. I sent an email response and then I decided that the whole world should have the chance to read my words of wisdom…..

I’ve written a few books over the years. I can confirm that it is not a way to get rich, but at least it is a hobby that doesn’t run at a loss. I’ve self published and used a publisher. 

  • It is surprising how many typos get through when you self-publish. You have to work really hard (and show your text to loads of people) to get the same level of mistake detection as you get from a good copy editor.

  • A good technical editor adds a huge amount to a text. If you are self publishing see if you can persuade someone to take this role. Perhaps offer to pay them with a signed copy of the book. Or a nice piece of cheese.

  • Lots of pictures can make your book file large and unwieldly, but to the reader opening a book and seeing a pair of pages of dense text can be a bit demoralising. Settle for diagrams and cropped screenshots that might be less version sensitive.

  • Don’t be afraid to talk directly to the reader. When I started out I tried really hard to put things into the third person for no good reason. It’s painful and people don’t like to read it. Address the reader as “you”. Have a conversation with them. And for projects you can say “We are now.....”

  • Never say something is easy. It trivialises the point and makes the reader feel stupid if they don’t understand it. Instead tell folks how powerful the technique is and how useful it will be once they get it.

  • Context is key. Don’t tell the reader how a for loop works, tell them the situations in which a for loop would be useful, with a side order of when not to use them and how they can go wrong.

  • Readers love narrative. If you can make the text into a story or journey that will be a huge win.

  • Round things off at the end and provide a trajectory for the reader to take what you’ve told them and go further.

  • Use verbs in chapter titles – “Make a whatnot” is a quick way of setting a context. Just giving the name of a tool or technique as a heading won’t help the reader as they don’t know what it is. If you want to name the technique say “Make a whatnot with a whatsit”

  • Treat your first pass of the material as the “ore” that you you’ve mined. You then have to refine it into the finished content. Don’t be afraid of making huge changes at this point. You might have to rearrange or dump large sections until it feels right. I find that I have to “go and live” in a chapter for a week or so until I’m happy with the sequencing and content.

  • I went to a session about writing a long time ago and they talked about “Killing your favourite children”. By that they mean that you might have a chunk of text that you really like the look of, but it doesn’t really fit the context of the piece that you are writing. In that situation you need to dump the text that you love.

  • Never really throw anything away. I keep a folder called trash where I put stuff that didn’t fit (see above). Maybe it will come back as a blog post or in a different section.

  • Look at writing tools. I’m playing with something called Scrivener (https://www.literatureandlatte.com/scrivener/overview) which I quite like. It makes it very easy to organise and sequence elements (which can be given separate synopsis sections). It also has very advanced output options where the same text can be compiled to generate different output formats. I’m hoping that it will make it easy to make epubs, word documents and html pages. It’s looking promising so far...

  • Treat what you have written as collateral that you can always find an outlet for. This email is going to turn into a blog post 😊 - and it did

Happy Flying with Microsoft Flight Sim

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we think this plane is definitely happy

Going flying is now a big social thing in our house. Three of us go flying together once a week and on weekend afternoons we get together over coffee and then go for a flight using the TV in the living room. Today we took a flight round Australia, what with the new landscape pack just having been released. They keep on about this “metaverse” thing. I think bits of it are already here.

Stop your glasses fogging up when you wear a mask

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I don’t see wearing a face mask as anything to do with personal freedom. To me it is more like a way of not killing myself or others around me. But if you wear glasses a mask can be a bit of a pain because a mask makes them steam up.

Chris told us that these work really well. So we got some and yes, they are awesome. You have to make sure your glasses are clean and then use the cloth to apply whatever chemical magic repels water vapour. The coating lasts a day or so and the instructions say that the cloths are good for lots of applications. We’ll see about that, but for now they are working a treat. Recommended.

How not to migrate Animal Crossing island data

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Home sweet home

I’ve just got a new Nintendo Switch. I’m in the process of selling a bunch of stuff from the loft that I don’t need any more and I reckoned I could raise the price of a new OLED one. I got it today and it is lovely. The screen is really impressive.

Moving your settings from one Switch to another turned out to be one part smooth process and one part white-knuckle terror ride. It started well enough. Once the new switch was online I was able to authenticate using the phone and I was asked if I wanted to copy all the saved games and settings from one device to another. “Yes please” I replied and progress bars grew and shank. At the end of it I was asked if I wanted to delete my Nintendo identity from the old device. I said yes, because it is going on sale to pay for the new one. Feeling rather smug at how well that had all gone I then loaded Animal Crossing into the new device and opened up my little island.

It wasn’t there.

And I’d just disconnected myself from the old device. I really thought I’d lost everything I’d built up over hundreds of hours of gameplay. I didn’t know (although I should really have worked out) that Animal Crossing saved games are managed outside of normal game saves. So my island was still on my original old Switch. But could I get back to it? It turns out that I could. I re-registered myself on the old Switch, opened up Animal Crossing and was then given a chance to claim my island data which had been left lying around on the device - presumably to deal with situations like these. I was then able to use the Island Transfer tool to move the island from my old Switch to my new one, and that worked a treat. I can now wander around picking up weeds in splendidly sharp colour.

The takeaway from this is to use the Animal Crossing transfer tool if you are moving your island from one device to another, don’t expect the device transfer process to do it for you. I’m impressed that you can recover from the situation; but I’m rather annoyed that I had to do it in the first place. If at any point I’d accepted the offer to make a new island I dread to think what would have happened. I’d have lost the lot. A prospect that felt a lot more scary than it probably should be, what with nothing particularly real being involved. I really hated the idea of losing all the digital chums that I’ve made over the years, to say nothing of all the digital loot that I’d accumulated.

Making videos with OBS and Camtasia

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After many years of trying, I think I’ve finally found a decent workflow for making videos. I’ve always loved Camtasia for making screencasts but I really like the flexibility of OBS for getting video onto my computer. So now I use both. The only thing I needed to do for it all to work was to go into File>Settings in OBS and change the video recording format to mp4:

Once I made that change I could import my recording files into Camtasia. It asks me if I want to use 60Hz video for the project (oh yes I do) and then lets me get on with formatting the video, adding captions, sorting out the audio and finally uploading it straight to YouTube. OBS is free and Camtasia has a really generous free trial period. If you are thinking about making some videos these two tools are a great way to get started.

Full disclosure: Tecksmith were kind enough to give me a copy of Camtasia to play with as part of my Microsoft MVP award. But I’d been using Camtasia and liking it in my day job for a good while before I got the freebie.

Whatever happened to MouseTrap?

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You know how old people are supposed to get cross about change? Wellllllllll.

They’ve changed the MouseTrap board game. The new one doesn’t let you eliminate other players by catching them. Instead you collect portions of cheese or something. Most unimpressed. I see this further evidence of the continuing decline of civilisation etc etc.

My advice: seek out the original and best. Proper sudden death action.

Upgrade your Circuit Python version in the Raspberry PI PICO

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My first version of the PICO MIDI Cheesebox used Circuit Python 6. And it worked fine. But I thought I’d upgrade to version 7. This turned out to be harder than I anticipated because of my less than stellar hardware design. The Raspberry PI PICO that I use to control the CheeseBox is locked inside the case with no access to the all-important BOOTSEL button that you hold down during power on to force the device into firmware upload mode.

However, the good news is that you can use a couple of Python statements to get your PICO to reboot into firmware mode so that you can drop in a new version of Circuit Python (or anything else). You can issue the commands down the terminal connection. I used the Thonny program which provides a REPL connection to my Circuit Python powered CheeseBox (or Crackers Controller).

microcontroller.on_next_reset(microcontroller.RunMode.UF2)

This is the first command you type in. It tells your device to reset into UF2 mode next time it is reset.

microcontroller.reset()

This is the second command. It resets the device and makes it appear as as storage device into which you can load the firmware. Note that if you do this you will wipe the contents of your PICO so make sure that you copy anything important off it first.

I’ve upgraded the firmware for the CheeseBox on GitHub to Version 7. You can find it here:

https://github.com/CrazyRobMiles/PICO-MIDI-Cheesebox

Tax Paid

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I’ve done my tax for the year. Just six days before the deadline. Go me. Now, if you’ll excuse me I’ve got some crying in the corner to catch up on…

It didn’t used to be this way. I was happy to pay may tax and watch things around me get better and better. But to think of the possibility that some of my cash is being used to fund the incompetence and maliciousness that passes for government these days is rather upsetting.

KidiZoom Camera is awesome

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Number one granddaughter has now reached the grand old age of “nearly five”. For Christmas she was given a Kidizoom printing camera. Lucky girl. The camera is awesome. The pictures it produces are OK with a fixed focus, wide angle, low resolution sensor which is as good as it needs to be. You can get shots off the camera by using a micro-SD card. Or you can print them in black and white on the built-in thermal printer.

This would be fun enough, but then the camera makers went to town with extra features. The camera has a colour LCD panel on the back, so there are a couple of games you can play. There’s also a bunch of image filters and some very clever extra things you can do with the printer. You can print mazes, a tie or even your own money with your picture in the middle. Really great fun.

The heck with the grandchild. I want one of these…..

Broken hard drive

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The hard drive above is broken. It contains 500G of - well, I don’t know what. I’m sure nothing on there is important because I never leave important things on portable (or indeed any) hard drives. And I don’t own any bitcoins. However, I guess you never know.

I was hoping that I would crack the drive open and find a drive and a USB interface card I could swap out for a possibly less broken one. However, that is now how things go these days. The drive and the interface are all one broken component.

What would be amazing is if a ninja reader of this blog took a look at the board and went “Oh yes, just tap this connecter and all will go well.” In the unlikely event that this actually happens it turns out that Brian has a similar vintage drive which is also broken in the same way…..

Police Squad and Rust at the Hardware Meetup

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Another fun hardware group meetup last night. In between chats about Python, Rust and thermal cameras I mentioned the TV series Police Squad. You can find it on YouTube here. It is one of the funniest TV shows ever made. They only made 6 or so episodes for some reason - but in a way I’m pleased about this as it never got time to go off the boil or become stale. It is just continuous, brilliant, genius. Take a look and thank me later.

Oh, and the next hardware meetup is on the 3rd of Feb. Find out more here.