More on e-paper

I have learned some lessons, so sharing with you.

The 7.5" e-paper are fun, I have loads of them with the nice laminated glass and black border to sell, plug, plug!

But the story of making e-paper work is not simple.

Software

This I am good at, and the latest code allow a range of widgets and extracted values to be displayed in various ways on the display.

Hardware

This is where I am also always learning. To explain, even in software, where I have being doing this for what 50 year, and have a degree, even now I learn lessons.

But hardware is more challenging for me - my formal training is less, but not nonexistent.

But the real challenge is the turn around time - software I can recompile and try in minutes - hardware is days or weeks to try out as a proper PCB, days if I solder and don't have the components yet. I have done milled PCBs which make that easier in a way, well, quicker, at least.

Symptoms

So..., what happened? The issue was with the larger 7.5" e-paper displays which I have used for years - I have on my doorbell display and my fridge. There is one at the Indian restaurant and two at the pub. They work flawlessly.

What happened is trying one for some other people, and they wanted a displayed image, and that created "smearing" over the display. It looked shit.

It seems some graphics, and I have concluded it is those with a lot of black/white transitions across the display line, break down in an odd way.

The fix?

I assumed it was me, and did loads and loads of tinkering with different LUT settings, and temperature compensation settings and VCOM calibration settings and all sorts.

I got it working OK, but it created a new problem!

Fading and burn in!

It is not actual "burn" in as such but it has the same effect - a lingering image. What is worse was random fading - even 1 minute updates would fade away showing burned in images within seconds. But only some times.

Two factors - one was not doing a POF command, and that creates massive burn in within hours. Even now, at the right angle, on some of my test panels, I see that I tried this on "MONDAY". Do not do that ever!

The other is the LUT was working to push the KK and WW frames a lot, and that left the panel in some state with a charge that meant any change could leave this fading effect.

The effect would eventually dissipate if the display was constant but it could take hours.

This was clearly not the fix I had hoped for.

Henry

So what was the answer? Well, if resistance is futile, inductance is king!

The boost circuit I was using was based on a known working design and used a 10uH inductor. But that was for a watch, a small e-paper display.

The reference circuit Waveshare do has a 68uH inductor. I tried that, it helped massively.

But testing showed that bigger is better! So now it is a 470uH inductor. And that is amazing.

I can do normal changes and updates with no smearing effects in any way. My fudged LUTs still break, and make a fading effect but they are not needed - I can do simpler LUTs and not have issues.

The results are amazing - I can do a non flashy update which is not causing burn in and full updates that work. I have applied the Waveshare v2 panel LUT for full (fast, flashy) update as well. It does full "flashy" updates a lot over night to try and clear any unwanted charge, just in case.

So finally I have cracked my months long e-paper headache.

If you got one of my older controllers you may not even see a problem - it only happens with some graphics, but if you have an issue the fix is a simple component change - ask me if you need a new 470uH indicator sending.

Do I have to pay council tax?

Apparently I have to pay my council tax by CASH monthly...

This is a shock, honestly! I would normally pay by bank transfer for whole year up front.

But OK... Except.

Err, OK, so do I have to turn up each month with cash which they cannot accept?

To be fair, if that saved me over £3k a year in council tax, I'd do it. I'd video record each attempt to pay, obviously, for a judge if they tried to take me to court.

Apparently "Cash is the default payment method that the council tax system uses for payments other than direct debit. This does not mean that the payment has to be made in cash."

As they seem confused, I have asked...

We'll see.

Hamsters

You may or may not know, there is a porn site called xhamster - I have literally no idea why it is called that. 

I'll save you visiting the site to check: Even though it has a cookie banner, it has no attempt whatsoever to operate the age verification required by the Online Safety Act. Not even a simple "I am over 18" button (which would not comply).

Yet, it is reported a forum for people with pet hamsters has shut down, along with hundreds of other sites and forums run by volunteers and individuals, because of the risk of fines and cost of compliance with this crazy new law.

OFCOM reportedly consider the costs of compliance for small sites “are likely to be negligible or in the small thousands at most”. Even without the risk of a fine of up to £18,000,000.00, the costs of "small thousands" of pounds, which OFCOM considers negligible, is more than a small volunteer site can bear, understandably. We are not talking businesses with income and a budget for legal fees here!

What is especially frustrating is the unknown - I don't know if this blog is in scope, and if so whether google or I personally am at risk of a fine. Worse - actual lawyers don't know either. I don't know if my GitHub repositories are in scope, and if so whether GitHub or I am liable. I don't know if my single user mastodon instance is in scope, etc... OFCOM have even admitted that they have no definition of "email" (one of the exceptions - yes you, or kids, can be on a porn email mailing list with no restrictions under this law). I have, again, written to my MP asking these questions.

A fun one, I do not know: If my blog is in scope as it has user generated content (comments), if I stop publishing comments (i.e. they get emailed to me, which is out of scope, and maybe I paraphrase and reply by an edit on the blog post) does that make it out of scope, or do I have to delete the user comments from before the new law came in to force as well?

Think of the Children, indeed, but making millions of individuals with small sites comply, at a cost of thousands of pounds each, is just crazy, especially when the law is not even doing what it aimed to in the first place.

By the way, my personal view on porn is that we need better education for children on the nature of porn as entertainment, and how actual relationships are not the same - after all we allow crazy violence in TV films and shows as entertainment, which people know is not "real" (even for <18 rated films where someone blows ups the planet, etc), but have a hang up over porn for some reason. At the end of the day nothing will stop a teenager with hormones from seeing porn, so let's accept that and educate to make that safer for society. But that is just my view. You may disagree, which is fine.

“There is a simple solution – the Secretary of State can exempt small, safe websites from onerous Online Safety duties, and protect plurality online.”. In practice this could be suitably worded so that small sites (by some measurable metric), and non business sites, etc, only need to comply if explicitly notified by OFCOM. This would mean no loophole for small sites that are actually porn sites, but provide the reassurance for those with pet hamsters to be able to continue their forum.

Stroke

The NHS have been very thorough investigating the stroke I had.

Thankfully the ongoing effects are slight - my typing is still more iffy than it was before, but good news.

They even did an ultrasound on my heart to try and find the underlying cause.

The good news is they found nothing. Well, I'll take it as good news. It also means they could not explain it, which is not so good. But given I had a stroke immediately after COVID, that seems a likely cause.

However, the one thing I find odd is the NHS efficiency here. The letter arrived this week (13th March 2025).

So what happened. I don't think even Royal Mail have a 17th class post that takes 6 months to deliver a letter. So that is rather weird.

Right to private communications

The European Convention on Human Rights protects the right to respect for private life, the home and correspondence. This includes protecting the privacy of messages, phone calls, and emails.

But UK and EU governments are trying to break that right in various ways.

So some thoughts.

1. Encrypted communication is a thing, it exists, it cannot be banned, it is just maths. I have done a nice video on how to make an uncrackable entirely manual encryption (one time pad) here.
2. Criminals can use encryption. My video is an extreme example, but in practice the tools to do this electronically in many effective ways exist and can be used by criminals, and MPs.
3. There are even ways to use encryption in a way that is mathematically impossible to prove you are doing - steganography - where there is no way to tell your encrypted messages apart from random noise in say an image or video.

What this means is that even slightly savvy criminals are safe. The tools all exist and are easy to use. The only issue is if non criminals like you and me can expect that right to privacy.

The Investigatory Powers Act (on which I commented, and was a witness at parliament) did, and does, try to crack encryption as a legal process, maybe, the wording is not ideal. Apple's news on this is one of the key examples. Not the first and not the last, and not something that actually tackles criminals using encryption, it will just make normal people way less safe. Remember criminals can use encryption!

One of the challenges for most normal people is how to use encryption. Most people do not care, or know, why they should even. But there are many ways. The old school ways are using PGP email, which is complex but that is no longer the case. There are many apps and ways to communicate securely, and the obvious ones are things like iMessage (for now). Apple designed it to be secure. But also WhatsApp and Signal.

The problem is that any organisation operating any messaging system that is secure is subject to secret orders from governments to impose back doors.

There are even calls for scanning content for illegal material, which only works if a service has access to the content. This has so many problems, apart from breaking basic human rights. And, I remind you that the "bad people" with "illegal content" can always encrypt what they do anyway, and even secretly if they want to. They actually have an incentive to take the extra steps that normal innocent people do not. The only problem is removing privacy for normal people.

So now to come to the main point of this blog...

Delta Chat

This is an app that works with email, it connects to your provider's email server (not all providers work, but many do, using IMAP and SMTP), and allows a more traditional style messaging app that makes encrypted communications simple.

It is clever, well done.

What is extra clever is this is just an email client. It is not a service that is subject to either Investigatory Power Act or Online Safety Act. Indeed, the latter explicitly excludes email, a term OFCOM consider everyone understands (really!).

But it makes secure encrypted chat a thing anyone can do, easily, in a way that legally there is very little that can get in the way.

So worth considering.

Muddled?

I have been advised this is all a little muddled, and I agree.

• IPA issues with Apple in the middle of OSA coming in to force
• OSA not applying to email, but OSA is not directly an encryption thing, probably.
• EU trying to do content scanning which means service providers having access to content.

I agree, it is muddled, and I bet that is intentional for some, but this is to try and say there is a way to chat, encrypted, with no scanning content, and no age checks, all in one, and easy to use.

More with E-paper

My previous code allowed a number of settings to be stacked up to suit all sorts of needs - a clock, day of week, sunrise/sunset, and even bin collection details.

I have started a new version now, at https://github.com/revk/ESP32-EPD

This is around the idea of a stack of widgets, each placed on the frame buffer.

This would seem a simple approach - and each widget can be positioned and aligned as needed. The idea is to have at least the same functionality as before, but allow me to work on more and more widget types over time.

So the basic widgets are:-

• image
• text (choice of two font styles)
• digits (i.e. 7 seg so cleaner in-situ updates on e-paper, intended for a clock)
• QR code

But even then it is not simple - I have some content substitutions to allow display of $DATE, $TIME, $DAY, $IP, $SUNRISE, $SUNSET, and so on. This makes a simple clock very easy to do.

Text

Whilst most of the above are simple, I have done a few extra bits - allowed multiple line text. Added some characters to 7 segment font to allow display of hexadecimal and the like, etc.

Images

Images were, however, a major change. previously I had full frame (for this 480x800) 1 bit per pixel (48000 bytes) file. Easy to make with some scripts. I also had some similar (smaller) icon files for the bin collections, but they need to know the image size to work.

I wanted more, and I wanted easier.

For a start, for E-paper, there are some more things I need from images.

• Would be nice if image file said size so I did not have to know in advance and users would not have to make images a specific size
• Would be nice to allow transparency, so one image on another can work without solid rectangular borders.
• Would be nice to allow not just black/white, but black/white/red for 3 colour E-paper.

None of these work for the simple 1 bit per pixel images.

So, for that reason, I have moved totally to PNG files (as per previous blog post). I have yet to code the black/white/red, but I can now.

Masks

One change I realised I needed was a plot mode - does text plot black background and white text, or just white text, or maybe just black text, etc. So I now have invert and mask operations on all widgets. 

Seasons

The system still has a season letter E=Easter, M=FullMoon, X=Xmas, etc. And allows that season code letter in the image url, so that works.

Bins

Bins (i.e. which bins to put out next and when) are the remaining widget to re-do. PNGs for the icons will make it way easier.  No need for fixed size icons and pre-converted images.

I plan to define a simpler and clearer JSON format and implement (and document) that first, but that will be soon.

More widgets

There are a load of obvious ones to add...

• Weather from an external weather URL, to show icon
• Weather to show min/max temp, maybe a $MINTEMP/$MAXTEMP or something. Adding ℃ to my font may be a challenge.
• Might be fun to add some sort of delivery tracking estimated time some how - but this means knowing tracking, and so on. Something too think about - a sign in the hall showing we expect a parcel would be really useful.
• I did previously have an SNMP uptime thing, I could add that back.
• Well, what else?

The nice thing is adding widgets is pretty simple with this structure, just more widget types in the config and the code to back them.

Confidence

This is one of those more personal blogs.

This week, well, started last week, I had a small technical challenge. The exact details do not really matter for this. But I'll explain.

I wanted to code something - something that was not quite readily available (some people had things very close to something I could just use, but not quite, which is where it gets fun).

The boring bit: It was a system to decode PNG image files, and allow me to use them in an embedded system driving a e-paper display. The details do not matter.

All that matters is that it was not easy to do - it involved understanding a detailed technical specification (PNG), and a new thing (zlib) which I had not used before. For a change the specification is a really really good one, which, in many ways, makes it easier.

Can I do it at all?

A biggie for me is should I, can I, even embark on this project.

To be clear, I have no reason to. Nobody wants this (well they may now), nobody needs this, nobody is asking for this, nobody is paying me for this. It is solely to make an e-paper thing I have easier to use. It is educational for me, a challenge.

Indeed, many of the helpful suggestions are to use a different file format, and not png. I do that already, but I wanted to make it simple - all can handle "save as png" I feel, so can I make it handle png. All and every format for png though?!

The protocol - the file format, which I literally sat in hot tub for over two hours reading, is good. But has some tricky bits. One is the compression/expansion using zlib, something I have never done.

I was seriously concerned I could make this work at all. Could I do it? Could I do it in a way that fitted in memory on an ESP32? Am I up to the job?

Yes I can!

I decided to go for it, in linux and then ESP32 code.

Each step worked well, and was not an issue. Minor changes as I coded. Lots of testing. zlib is easy, it turns out. zlib works on ESP32 too.

PNG has a lot of options, and as a decoder you have to handle them all. As an encoder you can be picky, but decoders cannot. I had to slog over the different options - make every one work properly.

In a day?

I spent a day, well, until early afternoon, and then a couple of hours next day. Total time under one day's work.

It works!

It went perfectly - the bugs were simple to fix. When I slept on it, all the remaining bugs came to me in my sleep, like they used to.

Not lost it?

So no, I have not lost it!

The work was not as easy as it used to be - younger me would have worked on in that evening and not next day. Younger me would not have made as many typos (way more since I had a stroke). But the results is good.

I worry about "losing it", and "imposter syndrome" all the time. I hope this is is a good sign I am not a losing the plot, honest.

Here it is https://github.com/revk/ESP32-LWPNG