Lazaras
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Joined: Fri Jul 10, 2015 7:55 pm
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E-Reader Questions

Mon Jun 26, 2017 3:34 pm

In another of the long line of 'I want to build a raspberry pi tablet' topics... Questions geared towards 'I mainly want this to be something for e-book reading.

Please note I intend on using a raspberry pi zero for this with potentially a micro usb hub that's 'solder on your own bits' to split the single micro connector either for hardware buttons plus a free full sized usb port, or to have a built into unit keyboard plus a free port. Also will want to de-solder the charging plug to solder an extender cable in its place so the plug extends outside of whatever casing. Unsure if I can do this for HDMI but would like to. Will definitely want to do something of this nature for the RCA jack so there's a video/headphone jack outside of case.

1. What lightweight software exists that lets me read epub under linux? Bonus if it has easy interfacing elements once it's open.

2. Any recommendations on 'tablitifying' the desktop? What Desktop Environment would best suit something like this? The end goal being 'I do not want to touch a keyboard during routine operation.'

3. Currently looking at GPIO as interfacin gfor monitor since I'm aiming at the pi zero. Suggested resolutions I should be aming at? As in could I get an 800x640 display? What resolution would give the best mix between 'the pi isn't struggling to render' and 'I can comfortably read the text'?

4. Suggestions on how to handle power management? Personally I would like to be ableto hit a button and the pi does a graceful shutdown, or hold that same button and it cuts everything off NOW. Other goal is 'even if the battery suddenly conks there's a super capacitor or something of that sort in place that would give the pi enough time for a graceful shutdown, and a way for it to detect that it needs to do an immediate shutdown using that capacitor's stored power rather than assume everything is OK.' I do not know if this is possible. How do i have the pi's power wire to battery but also take power from AC if there is no battery present? I hated that about my android tablet, it going 'oh there's no battery' even if it was on mains.

5. This entire project assumes i can get assistance in soldering. I am scared out of my mind because i know this is too big for me to do by myself. I just know I'm tired of the things I own breaking down around me, and i figure something DiY might be slightly more robust.

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stefanv
Posts: 36
Joined: Wed Oct 19, 2016 12:08 pm
Location: Ontario, Canada
Contact: Website

Re: E-Reader Questions

Fri Jun 30, 2017 1:12 pm

I can't help with the software, as I haven't tried any packages for this yet, but having just built a Pi tablet, I do have some thoughts on your other questions:
Lazaras wrote:2. Any recommendations on 'tablitifying' the desktop? What Desktop Environment would best suit something like this? The end goal being 'I do not want to touch a keyboard during routine operation.'
I find that stock Raspbian, together with an on-screen keyboard (xvkbd is my preference) and a gesture interpreter (twofing) works great as a tablet OS (for geeks anyway).
3. Currently looking at GPIO as interfacing for monitor since I'm aiming at the pi zero. Suggested resolutions I should be aming at? As in could I get an 800x640 display? What resolution would give the best mix between 'the pi isn't struggling to render' and 'I can comfortably read the text'?
I'd really suggest going for a Pi 3 and using the official touchscreen. I don't know how feasible GPIO interfacing of a full display would be. I suspect it's not very feasible at all.
4. Suggestions on how to handle power management? Personally I would like to be ableto hit a button and the pi does a graceful shutdown, or hold that same button and it cuts everything off NOW. Other goal is 'even if the battery suddenly conks there's a super capacitor or something of that sort in place that would give the pi enough time for a graceful shutdown, and a way for it to detect that it needs to do an immediate shutdown using that capacitor's stored power rather than assume everything is OK.' I do not know if this is possible. How do i have the pi's power wire to battery but also take power from AC if there is no battery present? I hated that about my android tablet, it going 'oh there's no battery' even if it was on mains.
An AdaFruit Powerboost 1000C will take care of most of this, including charging the battery, and operating the Pi from the charger instead of the battery when it is connected.

A tiny modification, and the addition of a capacitor, two resistors, two diodes, and a DPDT switch, will get you the ability to just turn off the switch, yet inform the Pi that power loss is imminent, so it can do a proper shutdown. It can also warn the Pi that the battery is about to be dead (using the Powerboost's LBO output).
5. This entire project assumes i can get assistance in soldering. I am scared out of my mind because i know this is too big for me to do by myself. I just know I'm tired of the things I own breaking down around me, and i figure something DiY might be slightly more robust.
I'm afraid you're not going to be able to avoid soldering for this project. I don't think there's any combination of off-the-shelf plug-together parts that will do everything you want.
Stefan Vorkoetter: Programmer, hobbyist, amateur watchmaker, pilot, and collector of fountain pens, slide rules, calculators, and watches.

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