4.41 inch ePaper Display for the rPi

No, colour is generally better than monochrome, all other things being equal. But for outdoor use under an open sky a high contrast monochrome display is preferable given that any colour display apart from coloured ePaper is going to be washed out and hard to read, especially with direct sunlight on the display.
Thats no different from trying to use a viewfinderless camera outdoors on a sunny day, but you'll know that.
Because there is nobody at my club who is using a Kobo. Question posted on rec.aviation.soaring
It doesn't, but it does tend to get you a commercial device with standard standard APIs for accessing its colour display and touch screen, enough flash memory to install the app on and facilities for uploading maps etc and for downloading flight logs.
Indeed, and it gets you a device that is small, light, not particularly hungry and cheap. As I said, I have a feeling that LK8000 has been ported to it, which would mean that somebody has added code to use SPI or I2C to handle small displays. It has to be them since we know there are no suitable HDMI displays and, although the el-cheapo Chinese back-up video displays accept a composite signal, the resolution looks to be unacceptably low.
The Beagle Board might also do the trick, but (so far) its not been mentioned as possible hw for LK8000.
Some of the better varios are using 3D accelerometer arrays, but that's for gust sensing. Similarly, solid state blind flying panels are now common, good and quite cheap but lets not go there: they are for a rather different purpose.
Batteries. Wind driven generators cause drag which stuffs glide performance. 12v systems are almost universal (Light aircraft use higher voltages). I carry a pair of 12v 7AH lead-acid batteries which can easily run my electronics for more than the longest day.
Wander over one day, take a look and ask questions. Pilots are friendly and generally happy[*] to talk, answer questions and show you stuff
*
just don't talk to a man who is in the middle of assembling and pre- flighting a glider: he needs to concentrate on what he's doing. Propellers: some gliders do have them because they carry auxiliary engines: if conditions deteriorate they can fire up and fly home rather than ending up in some farmer's field. Usually the engines and props are retracted behind the cockpit so you can't see them and come out on a pylon when needed, but nose-mounted, electrically driven folding props and small gas turbines are becoming popular. However, piston engines are still the most common, if the most problematic - because they add a huge amount of drag when extended, which is a big problem when it doesn't start. Thats why electric and jets are coming in: electric always starts and an extended jet adds very little drag even when not running.
I fly a pure glider and usually winch launch rather than aero tow.
Depends: at one extreme the Antares 20E is a 20m span electric self- launcher with a pop-up 47 kW brushless motor and wings full of batteries. It has the power to take off and climb 10,000 ft. I have no idea what its batteries weigh. At the other end of the battery scale my pair of 7AH motorcycle batteries only add about 5 Kg to a glider with a normal flying weight of 280 Kg.
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martin@   | Martin Gregorie 
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Martin Gregorie
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Might the Kobo use a faster, more capable controller?
I wonder how much the update speed is affected by the transfer rate.
Off the top of my head, if you're sending every pixel down an SPI connection uploading changes to the controller will be relatively slow, but IIRC pixel flipping is a physical process, and so is also pretty slow. I'd guess a cheap bit-serial controller would be rate-limited by pixel flipping rather than the SPI transfer rate, but what do I know. A full refresh on that 2.7" display is taking about 30 uS to set a pixel, so how does that compare with normal SPI transfer rates?
Would I be wrong to expect a more complex and expensive controller, which might accept byte-wide uploads over some sort of parallel interface, could speed up the overall refresh by flipping several pixels in parallel or at least double buffer the uploads so it could accept uploads in parallel with pixel flipping.
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martin@   | Martin Gregorie 
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Martin Gregorie
Sorry if this has been suggested.
How about hacking the original Kindle w/ paper white display.
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Reply to
hamilton
What does any of that have to do with the Kobo?
Ok, so there is your device!
When you find out let me know. I'd be very interested in learning more about this app on the pi.
I don't know it buys you much over the rPi. It is a good board in many respects, but with the rPi 2, it's main advantage of a faster processor is gone.
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Rick
Reply to
rickman
I can assure you the limitation has nothing to do with the controller. It has to be in the display as it would be very easy to design a controller that would be *much* faster than a 1 second update. The HDMI interface you mention supports 60 Hz updates at full HD resolution. That's just not the limitation.
Why? There are 120,000 pixels. At 20 MHz the SPI can support 166 updates per second.
None of this is a controller limitation. That is all determined by the display. I don't know for sure, but I think the larger displays are divided into multiple sections that work in parallel. Otherwise the 10" display would be more than four times slower than the 4.41" display. The 7 and 10 inchers even have two connectors.
No point in speculating. If I can't get the info on rolling my own controller, I am probably drop the ePaper thing for another couple of years until they get their act together.
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Rick
Reply to
rickman
You asked about the Kobo refresh rate. Here's a video of one, illuminated by direct sunlight and running LK8000, which is news to me since I didn't know it had been ported yet.
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I tried timing it with a stopwatch but found it quite difficult to get accurate times off the video. All I can say is that a whole screen refresh is comfortably under 0.5 secs and scrolling through configuration settings is a lot faster than that.
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martin@   | Martin Gregorie 
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Martin Gregorie
Have you seen these?
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I found this from a search for 4.4" displays: it seems to be the 4.4" display in a plastic case with a battery and radio link. Is it any use to you?
The size and resolution are almost exactly what I'd want, but I can't use it because the refresh rate is too low at 3000/hour, i.e. 1.2 secs per refresh and its only bicolour (black and white - no grey scale).
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martin@   | Martin Gregorie 
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Martin Gregorie
I think that is faster than the update I saw at the Kobo site. So less than 300 ms.
I would say this is usable for any app other than a video type function. Next time I speak with the salesman from Pervasive, assuming he speaks to me again, I will ask why the huge discrepancy in update rates. I expect I am flying below their radar since I won't be buying 100,000 a year.
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Rick
Reply to
rickman
These sound like the same Pervasive displays we've been talking about. I'd suggest you go with the Kobo.
These are of no value to me. I'm looking for a bare display I can roll into my own product which has very different requirements from these devices. I need extended temperature and Ethernet comms.
They must have a pretty hefty battery to last 5 years even with just 4 updates per day. The radio likely uses more juice than the display.
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Rick
Reply to
rickman
I got the final word back from Pervasive Displays and while they offer an extended temperature range display, they have no extended temperature controller for the larger units and are not willing to provide interface specs so you can roll their own.
You gotta wonder what they are thinking...
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Rick
Reply to
rickman
Maybe that it's easier to cool an enclosure than it is a display, so their product range is sufficient.
Reply to
Rob Morley
I can't say I understand what you are saying.
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Rick
Reply to
rickman
Hmmm, this "extended temp range" you have been asking for.
What temp range are you looking for ??
Maybe Pervasive has enough sales for the temp range they do support.
Maybe they don't want to support the two systems you are going to build with their displays.
Maybe you can buy one of their systems and scope out the interface and build one from that information.
Then they are not obligated to support, but they will sell you as many as you want.
hamilton
Reply to
hamilton
You haven't been following the conversation. They make a display that is specified to work over an extended temperature range. That alone cost them a fair amount of money to develop. So it would be rather pointless to offer such a display but not offer a corresponding controller or a spec so you can roll your own controller.
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Rick
Reply to
rickman
Yes, I did not go back through the past posts to find the exact numbers.
Are you going to buy a few displays and reverse engineer your own chip set ??
Reply to
hamilton
The display I looked at was -25C to +50C, and the controller was 0C to 50C. Those are surprisingly small ranges - even the average e-reader is at risk of being exposed to temperatures below freezing. I could understand the display panel not liking low temperatures, but rather surprised the TCon IC can't handle it.
Theo
Reply to
Theo Markettos
I expect those are "working" temperatures, not storage temperatures--eReaders don't need to operate outside the limits of human readers. ;-)
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-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
Reply to
Michael J. Mahon
Of course not. I'm not going to try to divine the rules for making the display work correctly and without damage. I *would* like to have the full specification so I could design a controller in an FPGA. But if the display maker doesn't want to support me in that, I am not going to swim upstream. Clearly there is something going on with these products. It has occurred to me that since they are coming out with a new product where the timing controller chip is built into the display, they might just obsolete the current displays in relatively short order. Since there doesn't seem to be a wide temperature range controller available at all, I'm not sure I will be using these devices. I may have to go with an OLED for the time being.
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Rick
Reply to
rickman
I think that is just a matter of going for the minimum requirements needed at the time it was designed. MPico designed their own controller chip and likely didn't need a wide temperature range so they didn't
well... I guess not even commercial temps since it only goes up to 40/50
Maybe they couldn't make speed at a full commercial temperature range or
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Rick
Reply to
rickman
put on a coat and be warmed by my own body heat. My eReader doesn't give off much heat but needs to work well below freezing temps. The updates slow down and they have to draw a line somewhere. So they make it easy on themselves and the battery.
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Rick
Reply to
rickman

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