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Comment by reerdna | Hacker News Reader

Hey HN! This is my project. Hope you find it interesting. AMA.

This is awesome! This kind of extreme low-power application was the original reason I wanted Mosh -- I always thought it would be awesome to have a wireless (hand-cranked?) laptop that could run SSH and would only consume energy when (a) a key was pressed [to update the locally generated UI], or (b) it wanted to fire up the radio (on its chosen schedule, e.g. <1 Hz) to retrieve an update from the server of the "ground truth" UI and reconcile that with the local prediction.

Thank you! Mosh is great, I have found it very helpful at times in my day job. SSHing into servers in Australia from Norway, the latency was pretty bad.

Have not started working on wireless yet but I hope to get to it. The SoC i use has Bluetooth. Using it for a remote shell would be amazing.

That is such a nerdy wholesome story. Definitely will have to make an eInk, foot treadle powered laptop that runs Scheme and uses Mosh.

CPU -- we all have opinions on uCs. I see that your chosen uC has very low active power consumption, less than 10uA per MHz, suggesting under 1mA full tilt.

Have you run any tests to see if active mode is indeed the mode you're in most of the time? Or is it possible that other uCs that could have better sleep current can beat your uC of choice?

Screen -- I like the Sharp in pixel memory LCD screens, though 4 inches is a bit small. A bigger screen would be what I'd be searching for, but I also know that monitors use a surprising amount of power, and 4 inches is the biggest memory-LCD screen in my area as well.

E-ink, for all of it's faults, does climb to 7+ inches and beyond. But changing eink screens is surprisingly power hungry.

Bluetooth -- lol, there goes the power budget!! This uses what? Probably 10x more power than everything else combined? I/O is a necessity and it's a good feature, but I really do wish* it used less power.

Yes, it's nearly always in active mode now. I haven't done much to use the sleep modes at all, only "sleep until next keyboard interrupt" when the program calls (get-key). Measurement, selected portion is while rendering a fractal - so "100% cpu" - at 1.5mA. https://cdn.hackaday.io/images/4389961676068300828.png

I'm sure other uCs could sleep at lower power, but active mode was what I wanted to optimize for.

This is wonderful information! Thank you! That's 1.49 mA at 3.3 volts?

Yeah, matching pretty well the advertised 5mW. But uLisp is probably not using the CPU very efficiently and so not driving it to the max that could perhaps be seen with something like a well-implemented FFT.

Is this at 48 MHz or 96 MHz? I'm so confused about the 96 MHz stuff in the datasheet. There must be some drawback to 96 MHz, because if not, what's so special about 48 MHz?

Is that using the FPU, or are you doing all the fractal math in integer? I have this vague idea that using the FPU might cause it to use more power than integer code will (and might or might not be faster for fractal rendering).

Using the FPU I believe but quite inefficiently, most cycles are probably spent in integer operations and chasing linked lists for the lisp parser. http://forum.ulisp.com/t/barnsley-fern-in-ulisp/1087

48MHz is the most power efficient mode, you can run it at 96Mhz "burst mode" but apparently it uses disproportionately more power, I have not measured how much.

It's really exciting to see this stuff coming to life!

Does this display have the same nominal 2Mbps speed as the 2.7" one I've been using? I've seen people report that it works well at 6Mbps (and thus 60 Hz) but haven't tried it myself. I'm guessing that it would use more power.

Have you been able to measure how much of the power consumption is the display?

Yes, I'm running the display SPI at 2MHz which is ~25 fps. Overclocking it to twice as fast works just fine but uses significantly more power as expected. I did not try to go further.

Approximately 25%-50% of the total power depending on refresh rate. Worst case seems to be alternating black and white pixels, maximizing the number of transitions?

I haven't measured, but the way the power consumption numbers are written in the datasheet (for the 2.7" one) does imply that alternating black and white pixels like that is the worst case.

So the display is about 25% of the 4.9 mW number? That's exciting! How often are you toggling the polarity of the LCD field? I've noticed that when I unplug the display it continues to display the same data for about 30 seconds on what is presumably the screen capacitance, but the datasheet minimum clock for that is IIRC 10 Hz, and as I understand it, never switching the polarity will eventually destroy the liquid crystals.

One of the things I really hate about normal computers is how high the interaction latency is, and one of the really appealing things about these displays to me is the possibility of getting much lower interaction latencies using partial screen updates, down in the submillisecond range (plus 10–20 ms for the crystals to fully change state, but it should be visible before that).

Oh, responding to your email, I got this bounce:

    This is the mail system at host adjuvant.canonical.org.

    I'm sorry to have to inform you that your message could not
    be delivered to one or more recipients. It's attached below.

    For further assistance, please send mail to postmaster.

    If you do so, please include this problem report. You can
    delete your own text from the attached returned message.

                   The mail system

    <(your email address)>: host mx01.mail.icloud.com[17.42.251.62] said: 554
        5.7.1 [HM08] Message rejected due to local policy. Please visit
        https://support.apple.com/en-us/HT204137 (in reply to end of DATA command)

I removed your email address from this comment in case it gets harvested by spambots.

I wonder if a combination of eInk and pixel memory LCD could be good? Use them as two monitors, keep vim on the LCD, web browser or other documentation on the bigger eInk.

The Barnes & Noble Nook did this, except that they were using a conventional backlit color active-matrix LCD rather than a memory-in-pixel LCD like this.

There is clearly a crossover point at which this combination would use lower power, because the e-ink display uses zero power when not updating, and the memory-in-pixel LCD uses power even to retain the display. So as the update rate goes low enough, at some point the e-ink display will use less power. My vaguely remembered estimate of this crossover point is that the e-ink display starts using less power than the memory-in-pixel LCD when the update rate is less than about one update per hour.

to answer hellbanned canadianfella, if you think one per hour is wrong, i'm interested to see your calculations

probably without showing evidence, neither of us will convince the other

Presumably someone working on an e-ink device at some point ran the same calculation, and decided to use the e-ink display. Which means that e-ink being more power hungry if you update it more than once per hour wouldn't have been true

People building e-paper devices after calculating their power usage definitely doesn't mean that my calculation is wrong. First, they started doing it 16 years ago, and things have changed since then, in ways that have made e-paper less popular; second, power usage is far from the only consideration in product design.

E-paper has some real advantages over memory-in-pixel LCDs: as I said in the other thread, the whites are whiter, it's not glossy, it can do grayscale, some versions can even do color, it's available in larger panel sizes, it existed in 02007 when Amazon launched the Swindle, and it can continue to display Amazon advertising even when the device is entirely powered off.

None of these are true of memory-in-pixel LCDs (though the Playdate does display advertising on its memory-in-pixel screen when it's "off").

Moreover, the computing power budget for the Swindle and similar e-readers is also measured in hundreds of milliwatts, just like the screen. There's not much reason to worry about whether your screen uses 100 microwatts or 100 milliwatts if your CPU is using 200 milliwatts. Reducing your power consumption by 50% or 5% is never a critical factor in the success or failure of your product, because you could just add another 50% in battery weight if it were.

Ambiq didn't even exist until 02010, and didn't sample the Apollo3 until 02018, so to get even a single order of magnitude improvement in CPU power usage, Amazon (or competing vendors) would have had to cut the compute budget for e-readers by an order of magnitude, probably resulting in major increases in space usage, reductions in rendering quality, sluggish interactions, or all three, and certainly increasing development cost. Ambiq's CPUs are fast enough, but you can't just drop them into a new model of Swindle or Kobo and keep the same software; they have tiny onboard RAM, little support for offboard RAM (which would make power consumption balloon anyway), and no MMUs, so they can't run either Linux or any of the other e-reader software that's been developed for existing devices—it needs way too much memory.

For what its worth, my math was ~1 update per 15-minutes was the crossover point between memory-lcd and eink.

There's a lot of different eink and memory-lcd screens that could explain the difference between your calculation and mine. But all else considered, 15-minutes vs 60-minutes isn't much of a difference at all.

For most applications of updates-per-second (or at worst, a few seconds per update), low-power monochrome seems best served by Sharp's memory-lcd.

Agreed. Also, my figures for eink power consumption are very uncertain; possibly you were able to take measurements or get good datasheets, but I couldn't.

A thing I didn't mention is that there are actually eink applications that have lower update rates than this. Store price tags, for example.

I decided to try my math again and document it more carefully.

--------

https://www.pervasivedisplays.com/wp-content/uploads/2021/12...

Pervasive Displays has an oscilloscope measurement of 3.75mA on their 5.9-second updates for their 1.54" eink screen. (Page 14). That's 22.125 mCoulombs of electrons.

--------

https://media.digikey.com/pdf/Data%20Sheets/Sharp%20PDFs/LS0...

Sharp 1.2" memory-LCD (a bit smaller) has 12uW to 50uW on static images. Assuming 3.3V, that's 15uA worst case (0.015mA).

-------

22.125 mCoulombs / 0.015mA == 1475 seconds per update break-even point, or ~24 minutes.

So yet another number, but yeah, memory-LCD is just really good. Remember that the 1.2" screen from Sharp is a bit smaller though, so its not a perfect apples-to-apples comparison.

Either way, its a much longer period between updates than I was expecting.

Yeah man, thanks for this clarification, looks like I've been spending too much time tinkering with apps and I've gotten completely out of touch, haha

thank you very much! this is great!

lol

You could theoretically simply buy multiple of these screens and place them in a grid. Would be slightly annoying when you want to split one window across multiple screens, but I imagine it would still be much more useful.

I've played a Japanese arcade game called Jubeat, that's made up of... I think a 4x4 grid of small touch screens.

With the right interface and design, it feels fine. In particular, Jubeat has a different note assigned to each screen so the divisions feel very natural.

First hit from YouTube: https://youtu.be/LSGOAkyFW7I

Or maybe just natural to people who put in a bit of practice, lol. This is an expert level song pattern, it's not so bad at earlier levels. But it still shows off how the 4x4 screen effectively communicates a variety of button press timings to the player, combo counters, life, scrolling and other such details for this game.

I too have been investigating using eink displays, but the biggest issue I've found is refresh rates are often terrible especially with colour displays. Have you found eink displays with refresh rates <1s?

The E-Ink displays also use a lot of power at reasonable reading rates, like one Swindle screen update per minute seems to use about 100 mW. That's about three orders of magnitude more than the 2.7" memory LCD, which I guess is about an order of magnitude less area, so it's about two orders of magnitude more power per area. But the memory LCD updates at nominally 20 Hz and potentially much faster, so it's three orders of magnitude faster, so in some sense it's five orders of magnitude better than E-Ink.

I have seen a Swindle do partial screen updates much faster than 1000 ms. In fact, I originally wrote http://canonical.org/~kragen/sw/inexorable-misc/tetris.html to play in the browser on a Swindle, with update times of more like 100 ms. And I successfully used IRC on it, too.

The E-Ink display does have some good points: it's not glossy, it's available in bigger sizes, its whites are whiter, and it can do grayscale. But, for interactive computing, I think those aren't a good tradeoff for being orders of magnitude worse at power consumption and update times.

No, I did spend some time reading eink datasheets but in the end it seemed too hard for me to do on my own. There's the Kindle and Freewrite so it seems possible

I find it amusing that this computer you built has better specs than the first family pc my parents bought us in the 80s.

This is a RISC CPU running at 48MHz (capable of bursting to 96MHz but that requires too much power, see elsewhere in this thread by the project builder) which doesn't just put an 80s PC to shame, the SPARCstation 1 in 1989 was running a 20MHz RISC CPU :D basically this potato runs circles around anything from the 1980s except maybe the Cray-2 or such.

As do I. We had a 286 which this would easily outperform. It could probably run DOOM (with dithering) quite well if someone put their mind to it.

I doubt it. It only has 384 KB of RAM.

Apparently the original Doom required 4 MiB of RAM https://old.reddit.com/r/gaming/comments/a4yi5t/original_doo... but I'm pretty sure there have been ports to platforms that had less.

Most of that is static data, so if stored unpacked, a larger flash should be sufficient to make the game need very little RAM. Unfortunately, if I read it correctly, this one only has 1MB of flash. (oh: but SD card. That could work!)

thanks! these are good points!

however, if you have the sd card powered on all the time it will cut your battery life by about a factor of 30

Yeah, most of the 90s home console ports were to systems that had less than 4MB RAM. Jaguar, 3DO, PlayStation, SNES, 32X. The GBA also has less than 512KB RAM and a 16MHz ARM and had Doom and Doom II ports. Some cutbacks might be necessary but probably doable.

Also none of those systems had Flash, and they were all a lot slower, requiring more time/space tradeoffs.

The RP2040 has 264 KiB of RAM. RP2040 Doom: https://news.ycombinator.com/item?id=30672527

PS. although, the RP2040 has 2 cores and programmable IO controllers, which IIRC were pretty needed to deal with the low memory (and sound). I don't know how this chip compares.

Also, as I just realized, the RP2040 Doom author is also the Pico SDK (lead?) developer at Raspberry Pi Ltd.[1], which probably contributed as much to the success as the two cores and their PIO controllers.

[1] https://www.raspberrypi.com/news/doom-comes-to-raspberry-pi-...

You could build a ray casting engine, textures and maps that would fit in that easily. It might not be doom but something similar is possible.

you can get one with 2MB of RAM now: https://ambiq.com/apollo4/

Hi there! Neat project! Can you give us a rundown of some of its features? Which processor are you using? Do you intend to sell these or are you only creating a prototype?

Thank you!

Not many features of note - it runs arbitrary lisp code, has a simple graphics interface. You can save and load code and data/text files to SD card.

The processor is the Ambiq Apollo3 Blue, which is really what makes running arbitrary code with such low power consumption possible. 48/96MHz, 384k of RAM. https://ambiq.com/apollo3-blue/

There's an Apollo4 which is faster and has way more memory, but it's a tiny BGA chip which doesn't have an Arduino core and I don't have the skills to work with that (yet ...)

I hope to create a PCB for it at least, it would make the device tiny and sleek and make it a lot easier for others to reproduce. But I haven't been able to learn PCB design yet.

I'm not a professional, but have done some pcb layout for hobby projects. Are you looking for collaborators, or are you wanting to keep this a personal project? If so, I can be reached at my username@(googles mail platform).

One other thing, I don't see the stl/cad files for the case anywhere, I assume you're still iterating on that. Very cool project!

Yes, I'd love some help with it, or it would probably take me years. Schematics and stls (made in tinkercad) will be coming once I find the time. For now I'm spending too much time replying to comments but I'm enjoying the dopamine

No worries, enjoy the front page! If you can get me even napkin drawings of your hookups, I can do schematics. I work in kicad, and step 1 of a board layout is to do schematics, so it isn't much additional work to lay out the schematics nicely enough for publication.

The Apollo4 can also attach QSPI SRAM which could allow adding more RAM and perhaps allow running common lisp...

Available QSPI SRAMs seem to consume a lot more power than the Apollo4 or Apollo3 itself, and because they're also slower, they increase the processor's duty cycle, which makes it use more power itself (except when the user is waiting on it, I guess, or you're running a background compute task).

i love the minimalist concept of a laptop with so much battery life: Dell and Apple could learn something from this.

so that gray piece on the right is the solar collector, right? since it can go 2 years, what's to stop it from going forever? what if you added a 2nd collector on the left? how big would the solar panel need to be in order for it to run indefinitely?

Super job!

Thanks! The biggest obstacle to running forever may be the chemistry of the li-poly battery which has a relatively low number of charge cycles and is known to degrade over time. A promising option is li-ion capacitors or supercapacitors, which I'm looking into. This is the board I've purchased for testing. https://www.tindie.com/products/jaspersikken/solar-harvestin...

Id just personally go with replaceable parts. AA NiMHs are like $1 to $2 these days, and 6V 5Ah lead acid is like $20 (Lol, first hit on google is $4 from some no-name brand).

Replace the battery every few years and you're set. Rely upon mass production, standard part numbers and highly recyclable parts (lead acid wins at this).

-------

Lead Acid is particularly good at UPS style power usage patterns. It's very easy to perpetually trickle charge lead acid.

------

If you're set on Li-ion, then use a standard 18650 cell, so you know that you'll always be able to buy a replacement. But given the attributes I see here, lead acid probably wins. So you have to replace a part every 3 years that costs $5 to $10, big whoop.

No, no, no! This is the post-apocalypse laptop! You can’t go off buying new batteries in your mad-max car. It’s gotta work from that solar panel!

A post-apocalyptic backyard garage could conceivably recycle a lead-acid battery, they're pretty simple.

As it happens, I've spent a lot of time over the last week talking to a guy in Romania who's trying to fix a sulfated lead-acid battery in his backyard garage. (I don't know if you've been to Romania, but the apocalypse happened 40 years ago there, so his available resources are kind of limited.) I think he's going to succeed, and may eventually progress to being able to recycle the lead into a new battery, but it's not going to be a weekend learning process or even a week-long one.

He reports that it's a "very complex electrochemical device".

The USPTO (?) has assigned the code H01M10/06 to lead-acid battery patents. https://patents.google.com/?q=(H01M10%2f06)&oq=(H01M10%2f06) finds 44'593 patents in this category. You don't need any of them to get a working lead-acid battery, but a significant subset of them are going to be helpful. Some are order-of-magnitude improvements.

What kind of apocalypse happened in Romania 40 years ago?

I presume he's talking about the collapse of the Soviet Union, which caused a huge amount of upheaval in that area.

But I'm a poor student of modern history. Just throwing out a guess for now.

Right, but I got the time interval wrong; it was only 30 years ago.

That sounds like the opposite of an apocalypse

Eventually it was good for Romania but IIRC, the initial collapse was very bad for the locals.

But again, I'd say that Eastern European modern history is my weakest subject by far. I probably should avoid talking about this subject lol.

And in a Mad-Max future (lots of cars around, but not enough fuel), there will be plenty of Lead Acid batteries laying around to recycle.

I do consider it effectively an apocalyptic kind of battery design. It was invented in the 1800s, its chemistry is incredibly simple (Sulfuric Acid + Lead), and is very well studied.

i prefer the phrase "anti-apocalyptic." Because by designing an energy efficient laptop/phone, less lithium/capacitor resources are manufactured and everyone can have one, unlike that single coke bottle in that 80s movie, "The Gods Must Be Crazy" which will lead to one. ;)

Would it be possible to use standard 9v rechargeable cells? I’m sure the lifetime would be even less, but if a battery swap cost $10 and could be found at any corner drug store…

You can look into LFP (aka LiFePo4) cells, which have higher durability than lithium ion. Beware they have different chemistry so charging voltages differ from standard Li-poly or Li-ion (they are also safer, which is nice). I haven't looked at the data, but I suspect supercaps may not be optimized for very low leakage, and generally the energy density is not so good (though if you have access to energy harvesting I guess it may not matter!).

Did you consider the possibility of using a FPGA Lisp CPU? [0] I hope the supercapacitor idea works and you don't have a leakage issue.

[0] https://frank-buss.de/lispcpu/

FPGA soft core CPUs can't beat the same logic implemented in ASIC silicon in terms of static power consumption. The MCU at the core of this project has a very impressive uA/MHz specification that's difficult to achieve alone. I'm surprised to see it being much lower than even STM32L0 running off external SMPS

> i love the minimalist concept of a laptop with so much battery life: Dell and Apple could learn something from this.

Really? What? Put on a tiny black and white display?? No backlight?? Tiny processor?? No SSD?? No HDD??

I mean, this is awesome. And look forward to see where it is going. Not sure what Dell and Apple will learn??

Dell and Apple can learn that there are consumers out there who want low cost minimalist options with long battery lives and long operational lives. Not everyone wants to buy a brand new 600$ computer every 5 years. They can learn that some consuemrs aren't going to put up with the crap of planned obsolescence.

Not really planned obsolescence, just lack of spare parts. 10 year old laptop will work just fine, it will just be hard to get replacement keyboard or batteries.

> Dell and Apple can learn that there are consumers out there who want low cost minimalist options with long battery lives and long operational lives.

They don't want their business and low marigin sales.

Also Macbook air has what, 18 hours of battery life ? That's enough for vast majority of users.

A MacBook has up to 18 hours when new, but you can get far less than that.

The real advantage of long battery life isn’t so much the duration when new but both reducing the number of charge cycles and preserving battery life as the device ages.

> They can learn that some consuemrs aren't going to put up with the crap of planned obsolescence.

The number of consumers who not only complain about planned obsolescence but also put money where their mouth is, is tiny. It's easy to get people on board with the idea behind projects like Fairphone, but then they do a price comparison and buy a cheap Huawei.

The market for Linux laptops is already a small niche and those aren't all that limiting for users when it comes to processing power and software support. Now take away the modern web browser and very few people would consider it for anything more than a little tinkering.

Unfortunately this is almost the least profitable market segment imaginable and isn't going to be addressed well by capitalism.

I don't mean this in a "capitalist bad" way, it's mostly great but there are certain innovations and technologies that don't fit well with a need to get the most return possible on capital invested. There's a "dead space" of techs that would benefit everyone, need some capital to create - but don't allow a lot of value to be captured.

A bit like how we see more VC excitement about "vat grown meat" (a centralised industrial model that exacerbates supply chain dependency and further alienates people from their food - but is perfect for capturing value) vs working on "super potatoes" or algae-based systems that would be low-dependency and could scale down to individuals.

Orthodoxy is that government is supposed to help with this stuff but they have their own incentives (some of them a result of industry capture) which rarely align with decentralisation, degrowth or reduced dependency. For example recent battles to get laws passed to even allow you to repair your own stuff.

It did address it fairly well. They were able to buy cheap, off-the-shelf components and build this with relatively little work.

If you had said that there are consumers who want long battery lives and long operation lives and are willing to pay a premium for that, then Dell and Apple might have something to learn - but the existence of consumers who want a low cost option for that is irrelevant, since serving that market would just lower your profits by cannibalizing your sales to the people who are not only willing to pay $600 every 5 years but $1000+ every 3 years.

Hell yeah that’s some next level lisp hacking! Great work.

Thanks! Have not had the chance to do too much lisp hacking yet though, I still very much consider myself a beginner. Mostly solder and C so far, apart from implementing a crude text editor.

> Mostly solder and C...

Hey! I used to have those two and assembly on my resume as the only entries under "Programming Languages" !

Very nice project.

Have you ever been tempted to build a giant cyberpunk style magnifying glass into the computer to make the screen bigger?

I've been working on a similar project and if you're up for it, would love to talk to you in more depth about your project if you're game. I've been eying up the newer Apollo4 (having recently ordered the devkit to experiment with). My email is in my profile if you'd like to chat and trade information, ideas, or collaborate.

That's exciting! Would you mind if I emailed you too?

Sorry, I just saw this reply. Go ahead!

Very cool project. 2 questions:

1. How did you find working with the Sharp Memory display as a tinkerer? Did you like building with it and would you recommend it? It's pretty new tech to me and I've been mulling whether to splurge for it for a potential pet project of mine.

2. How's the refresh rate on it? Judging from your video it looks pretty dang swell. It looks to be a lot faster than the typical 15hz one sees on higher end e-ink displays available right now.

Using the Adafruit breakout board, I had no problems other than an SPI bug in the Arduino core. Be warned that they are fragile when not protected, I sheared off the flex cable on one which was not fun.

Official refresh rate is ~25 hz, unofficially they seem to be able to go a lot faster (2-3X) if you don't mind increasing power consumption. And it's faster if you update only some lines. But by then you have run into a limitation in how fast the liquid crystal can respond.

Do you think this could work well in the form factor of a programmable calculator?

Yes. A smaller, but higher resolution display is available from Adafruit, and they made a calculator tutorial for it which helped me a lot in the beginning: https://learn.adafruit.com/diy-rpn-desktop-calculator-with-c...

I love this. Thank you.

Wondering if you specced out or thought of an implementation with a e-ink display and internet.

How long can battery last for that base spec, with say 10", 13" models?

Ever hear of ChrysaLisp?

can you get a display with same technology but larger?

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