Show HN: Open-Source eInk Bike Computer (opentrailpaper.com)
Hey all, i just launched my Eink Bike computer project and think it is cool.
Another tidbit, in the crazy things that AI has done... It has helped create a ANT (common sensor wireless protocol used in workout/biking) implementation for ESP32 by messing around with undocumented registers: https://github.com/RaemondBW/esp32-ant
134 comments
[ 0.94 ms ] story [ 26.1 ms ] threadWeather sealing is quite doable if you accept you need a boatload of glue and you coat your 3d printed case with proper car lacquer or at least a thick coat of acryl. Use reinforced filament, and at least something 70c+ resistant (so no ordinary PLA).
I've driven it plenty in the rain in NL (not this display, my own).
The mess of different implementations makes it really hard to hack on and share this kinda stuff.
AI does make it really easy to figure out these protocols now so that’s nice I guess. I just flipped my bike upside down and hooked up a logic analyzer and it took LLM no time to figure it out… it is really impressive
It was quite a rich ecosystem of sensor devices, especially for cycling, including speed and cadence sensors, heart rate monitors, power meters, lights, radar, etc.
It has been extremely popular over the last 20 years.
eInk is the right display tech. I think this will do really well.
That said, I don't love needing a separate device, I really prefer to just plop my phone on my handlebars. So I'm building a bike computer app for iPhone: https://x.com/mholt6/status/2090529441944687087 (trying to get Apple to approve my developer account / business info, but they're hung up on my website of all things).
Phones are definitely not ideal in terms of display and energy use, but, I have found that with proper optimizations, energy use is a non-issue. To offset display problems, the app has several ride modes: a rich map display with 3D road or satellite view; a high-contrast wireframe map that looks great at both high and low refresh rates because it has no analog-style gauges; an instrument panel dashboard view; and a voice-only mode that has big touch zones for on-demand voice updates, using a state of the art mobile voice synthesis model. For connected radars, the app also renders radar data and has a screen like Tesla/Rivian's autonomy displays.
The app automatically manages thermals by switching modes to preserve battery life.
In my testing so far, by managing energy, making really good voice feedback, and using high-contrast screens (every mode other than the "rich" map), even a dimmed iPhone display is quite a usable bike computer in high-altitude sunlight.
But man, that eInk looks so clean and nice. Definitely the superior display! Nice work and I hope to learn some things from it!
Not sure I'm 100% on board with the visual style of your interface (some of the metrics look like they'd be nearly impossible to read while riding 30mph down a gravel road) but I'd love to check it out once it's released.
Do you have a way to sign up for release email or updates for your project?
Good luck!
The video preview I linked to only shows the rich maps and instrument modes. There's also a wireframe map view that is higher-contrast and much more practical for your gravel rides: https://i.imgur.com/lZF20Xz.png -- and I am still tuning of course, we can make the map smaller and the characters larger, etc.
Maybe follow @mholt6 on X for updates when I have them... whenever Apple will let me in.
It's interesting and I clicked on the OP, but why? The variable ambient light conditions, refresh rate, etc would seem to favor standard LCD/etc.
Battery capacity isn't much of an issue for a small screen, and weight carried by the bicycle.
Refresh rate is a solved problem for eInk as well, but it comes with energy tradeoffs and... might still be proprietary. But 60-120 fps eInk exists AFAIK.
E-ink, instead just lets the sun reflect off of it, does want some sort of light in the dark, but, perfectly visible in full-bright/direct sunlight.
1. https://www.panelook.com/ED047TC1_E_Ink_4.7_EPD_parameter_25...
Compared to the full contrast range of the sun lit real world, all displays emitting light function in a very narrow and very dark contrast range. An eInk display does not emit light, so in that environment you have a clear separation between bright and dark.
Even if it had been true, claiming the e-ink has the same or better contrast as LCD is still false. The sun-lit world has higher contrast than any display, yet it does not make e-ink's contrast any good. In fact it makes the low contrast display much worse as you are likely to be looking at much brighter scenes than your bike computer's screen immediately before looking at it and thus having even less ability to distinguish slight brightness variations on the low contrast screen. A transflective TFT display in bike computers also does not emit light, it's still higher contrast in the sun than e-ink.
Frankly, I don't understand why you are arguing, when it is so ridiculously easy for anybody to test for themselves. Just bring your LCD or OLED device out in the sunshine along with your eInk device and see which one you can read from more easily.
TFT displays are really good in the sunshine, but eInk is still a bit better, only beaten by paper for real world contrast.
Has it been a long time since you've used eInk? Maybe they were worse in the past? My oldest eInk device is from 2018, so I wouldn't know about the screens that were before.
You obviously have not done what you are suggesting. Paper is low contrast too, on the level of e-ink.
>Has it been a long time since you've used eInk? Maybe they were worse in the past?
No to both questions. E-ink inherently is low contrast and there is no way to enhance it in this technology: both black and white are done with a pigment, same as print, which caps at ~30:1.
I read books on my Kindle outdoors in the blazing sun, and so do most of the millions of people who have Kindles or similar devices. Contrast is excellent. In the same conditions an LCD phone is just a black mirror which you can hardly make out any kind of information form. An OLED is better, and you can see everything on the screen dimly if you strain your eyes. A TFT is even better, but none of them compares to eInk or paper.
So maybe you live in Britain or in Norway, or somewhere similar where it's cloudy all the time? You saying that paper is low contrast baffles me, actually. It seems like you are hung up on the contrast within the device, which is irrelevant for outdoor use, where the only thing which matters is the contrast as part of the real world environment.
Let me ask you, who is the faster runner: The fastest runner on your street or the slowest runner in the Olympics? Because you seem to be arguing for the former because of measuring within limits that do not confirm to the real world - where there is a sun.
Also, if you really try to do what you suggested - you should not use an LCD phone, phones do not have reflective LCD displays but use backlight instead so the contrast on those decreases with increase of the ambient as both light and dark areas reflect the same amount of ambient light and the only difference is the backlight's emissive portion, the higher is the ambient, the lower of the ratio i.e. contrast.
That is the internal contrast of a screen or printed material. I agree, and that type of contrast is important if the screen emits its own light.
However, for outdoors use the only contrast that matters is relation to the real world, aka physical reality. And brightness of course becomes the main factor.
Also, thanks for pointing out you are talking exclusively about transflective/reflective LCD. It seemed to me for a while you were talking about any type of LCD. But even so, eInk and paper has better contrast in real life outdoors use, because we have to measure contrast in the human eye and not within the device.
The human eye adopts to the brightness in the environment and makes a contrast "scale" according to this. The nearer your screen's black color is to the black of the human eye's black in that situation, the better. And the nearer your screen's white color is to the human eye's white, the better.
If either your black or your white is too far from the human eye's calibration, then your screen is no good to use, no matter how good the internal contrast of it is.
There is no limit to how bright things can be or how dark things can be. So the internal contrast between a very deep pitch black and a very dark gray can be 1:10.000, but within a real world sunlit environment it all just looks like black. And this matters, because direct sunlight is 30.000 - 100.000 lux, while an office is maybe 500 lux.
For you perhaps. I, for one, use screens to get information encoded in symbols and graphs, if all these symbols and graphs had no contrast with background I would not be able to distinguish them from the background. You seem to only care to compare the screen's brightness to the real world, perhaps losing your screen and then finding it in the real world, aka reality, is the main usage mode for you?
> But even so, eInk and paper has better contrast in real life outdoors use
You need to give a citation for this or are you using "contrast" do describe brightness? In this case I agree - eInk's "black" is just a darker shade of gray so it reflects more light i.e. contributes to higher albedo. It's not great when you are trying to read from that screen but if you are just looking for the lost screen in the wilderness it won't hurt I guess.
That being said, seeing that there are now eink displays capable of 60Hz, I wish they (and projects like this one) could take over in this specific market.
I've gone without a bike computer for the same reasons as not wanting a second device. I used my phone for years in a water proof front frame bag with a transparent cover. Usually for not more than 3 hours at a time. Only on my Pixel 7a did I end up with burn in from the Wahoo Android app's status screen, where "n/a" for not having a power meter ultimately burnt in after about 2 years, at least that's when I noticed it. Now I just go without being able to glance down and see ride stats or directions. More planning or stopping if I reroute is required, but I didn't want to damage the phone... :(
Presumably an app could cycle displayed screens, if that's what you meant by switching modes, to avoid burn in? But I really thought AMOLED was past that when I never saw it on previous phones.
your project does look amazing. sorry that the appstore team is holding things up.
RE: ANT+, a hackrf one and fable was key to the hack.
I attribute my iPhone 7's camera failing with mounting it on my bike.
I’ve wondered about this. Does it shake a lot less when it’s in a pocket for the same ride?
Presumably yes, as every cyclist ever does that.
That’s why the head units in my bikepacking groups have screens that double as solar displays. The Coros Dura is probably the most popular one for all day or multi-day trips.
I used a transflective LCD. Works fine. You don't need UV protection nor have temperature issues. (Yes also build my own two years ago but I don't do pr so no slick website).
It's not a preference. There are a slew of issues around physical damage. Running out of power is far more of a problem than you make it out to be. There are major visibility issues (thankfully Garmin is working on this by continuing their idiotic OLED push /s) and water ingress issues. 1M submersion rating is NOT "driving rain while riding at 15-20mph."
The only people I see with phones on their handlebars are newbies.
My thought was I'd love to set an HR zone and then connect it to my e-MTB and have it change power to keep me in a zone.
The refresh rate on my device was horrible, and the models (this was a few months ago) struggled to create a historical line plot of my HR.
But I don't see how they both fit together honestly.
Anyway, as long as you have fun doing this and some people enjoy it also, congrats!Maybe it would have fared better if I was out in sunlight viewing them, but seeing this thing in person sold me on e-paper for this use case
Not sure why needing less battery or having better at-a-glance visibility would be such a bad thing.
One need not love a device, that's ok. But digging to invent a reason to hate it also doesn't seem necessary.
What situation?
For others, some of those advantages do matter. Different strokes for different folks! Cheers mate.
it has a nice backlight (basically identical to a kindle display)
color is fair, but i dont miss it.
i do absolutely love how readable it is in direct sunlight (when im mostly riding)
A good UI design would mostly avoid the need for colour.
Anyway one thing I think would be nice is if the GPS radio can become a peripheral. Then with that architecture could the head unit just get GPS from your phone?
Why would they suffer from display scaling? At the same device thickness, larger devices have the same volume per cm² of display. And it gets better:
- if they need the same volume for electronics (likely mostly true; you may want a slightly faster CPU and more memory, but don’t need a larger GPS, second WiFi chip, etc), that means more battery volume per cm² of display.
- at small sizes, I guess/expect wall thickness of the case to scale slower than the dimensions of the case, giving larger cases relatively more internal room.
(Googling, I see the 550 is even slightly thicker than the 1050; 16,8mm vs 16,3mm)
And I think GPS is the key power consumption part here. Have you tried opening one of those background location tracking apps that would require your phone to receive GPS all day long? That significantly reduces battery life on your phone. You really want your entire GPS stack running on a power-sipping processor, not on your phone’s application processor.
If my memory is correct, at the price of only be able to sync your rides and routes using a proprietary app that probably also send all your data to mothership.
For me, the next step for this is taking all the sensor data recorded for a ride, and loading it into my own fitness tracking database that I own, control, and isn't tied to someone else's profits.
I openly admit, I have not spent much time researching this subject, was just in the back of my brain as I migrate away from SAAS and IAAS.
I hope we can get a better suited hardware though. Larger buttons, smaller device overall. 4.7" sounds huge, almost size of a phone.
the dealbreaker for me is whether it could eventually work with the Garmin Vario radar (which the Wahoo supports with a nice visualization) -- that is _literally_ a life saver and I no longer ride without it.