This is great, I just saw your post on X. I'm also building a bike computer!
eInk is the right display tech. I think this will do really well. It might need a UV filter.
That said, I don't love needing a separate device (hence, I don't own any bike computer). This is just my preference, but 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!
EDIT: Woah, you got ANT+ support using BLE radio? I am not surprised that that is possible, but dang, that must have been a clever LLM.
eInk does seem like an awesome choice for this to me too.
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.
I use my phone as a bike computer too but it only works on short rides around town. Anything longer gets cooked by the sun until the screen dims and battery stops charging.
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.
note using a phone mounted to a bike or motorcycle can cause damage over time to the camera assembly especially the motors used for OIS. depending on how much you ride or the quality of the roads you ride, it could be an issue.
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.
To each their own and the e-ink computer is a neat project. But I'm personally with you on not wanting a separate device. I have my iPhone and a quad lock case I swap on for rides.
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!
Thanks; not yet unfortunately, I have been too busy to set up a mailing list, but that's a good idea.
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.
For many, a separate device is a feature. Not using the phone battery and not poosibly damage my phone (fall) is good.
> eInk is the right display tech.
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.
In my humble experience the gold standard for bike computer screens was the Wahoo Elemnt Roam 2. It had like 64 colors or so but you could see it everywhere.
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.
eInk is like a piece of paper, which gets MORE visible in the sun, but standard touchscreen LCDs/OLEDs get harder to see. I am not sure about the physics/reasons for this. Phones also aggressively dim screens to conserve energy and lower temperatures. Phones absorb a lot of sunlight, so a white eInk display is brilliant in that regard.
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.
Trying to outbright the sun on a battery-powered device is an approach I've always found questionable.
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.
Transflective LCDs, which most bike computers use, are also reflective but have better contrast than eink making them more visible in sunlight. They are different than phones.
They don't have better contrasts. They have blacker blacks, but eInk has much whiter whites.
They obviously do. E-ink display in this topic, for example, is 12:1[1]. The best (contrast wise) e-ink displays available commercially are around 20:1. The trashiest LCD, on the other hand, will be around 500:1.
1. https://www.panelook.com/ED047TC1_E_Ink_4.7_EPD_parameter_25...
Measuring the contrast within the display means practically nothing compared to measuring the contrast in the real world environment, which in this case is outdoors and hopefully in the sun.
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.
> Measuring the contrast within the display means practically nothing compared to measuring the contrast in the real world environment
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.
LCD screen are pitch black by default. Eink can be white without extra energy
Yes, and there are many other tradeoffs. How do the tradeoffs fit this use case?
Because most people cycle outdoors and when the sun shines, and eInk is much better than any other display type in bright environments.