e ink display
entityfree (3332) 77 posts |
i am thinking about getting e ink. i know it says can use for signs. can i use it for computing? it says /full/ refresh rates 4 or 6 s. |
Glen Walker (2585) 469 posts |
That will depend on the type of computing you are wanting to do… I had a 1st generation Kindle which was great for text and OK for viewing static web-pages if it didn’t have too many images. The issue you will have is that unless the technology has changed since then I’m fairly certain that every change to the screen will require a full re-draw so if you were writing something then every time a character was typed it would re-draw the screen which would take a little time and also probably appear to be “flashing” at you (i.e., I think the re-draw mechanism wipes the whole screen first and then draws). I haven’t looked at it for a while though so would be happy to be corrected… |
Rick Murray (539) 13385 posts |
Technology has changed? My ebook reader has a command line and the browser can do animated GIF (sort of). It only redraws the part of the screen that has changed. |
Glen Walker (2585) 469 posts |
Well you know…updated…improved… I’m not claiming a fundamental shift in the laws of physics…
Hmm… maybe mine was just rubbish! Always thought that with a bit of development e-ink would make a great screen for a laptop and perfect for a phone but then I’d only be using it for text based things for the most part and I guess most people would want more media and stuff on their computers/devices? |
Clive Semmens (2335) 3122 posts |
Me too. I want to be able to do diagrams as well as text on my laptop, but you don’t need fast refresh rates for those, either. Happy(ish) with monochrome – after all, most of what I’m doing is designed to be printed, and most of it has to be monochrome because colour printing is expensive. |
James Wheeler (3283) 344 posts |
I would love an e-ink phone or PDA. Battery life would be awesome. At the moment I’m using an electronic notepad . |
David Boddie (1934) 222 posts |
The Yotaphone had an e-ink display on its reverse side and the follow-up phone looks interesting, if possibly a bit disappointing. Even my Kobo e-reader from 2013 can redraw the display in under a second, so modern ones should be better than that. |
nemo (145) 2437 posts |
Sony’s amazing FES Watch: Yes, the display goes all around the strap. |
entityfree (3332) 77 posts |
i wonder what my chances of dual displaying are. the e ink connects to the pins on the pi. like can i out to hdmi simultaneous. |
Glen Walker (2585) 469 posts |
It sounds reasonable to expect a dual display—definitely if the e-ink display is connecting via I²C |
Rick Murray (539) 13385 posts |
I think eink is SPI, IIC would be way too slow (unless you’re using a tiny display like 160×72 or the like). |
James Wheeler (3283) 344 posts |
IIC is more than fast enough for most eink displays based on current specs and refresh rates. |
Rick Murray (539) 13385 posts |
ORLY? For some reason, RISC OS 5 starts up with the IIC bus running at 100kHz. That’s it’s slowest speed, which was replaced by a 400kHz option in 1992, and for what it’s worth the 3.3V bus voltage spec came after that, so it’s a reasonable guess that almost anything “modern” that you are going to connect to the Pi is going to be capable of running at 400kHz (evidence: CJE RTC, CJE Power control PIC, the temperature sensor thingy, my OLED…). Anyway, default speed is an early ‘80s style 100kHz. That’s 100,000 bit transitions per second. If we assume that an IIC byte takes nine bits (eight data bits then an ACK), this gives is a transfer rate of 11.1KB/sec. Now let’s consider my e-book e-ink panel as an example of the largest thing you’re likely to hook to a machine at this time. It’s a pearl type screen, so 800×600 with 16 greyscales. For the sake of argument because I can’t be bothered finding a datasheet, let’s just assume it’s a 4 bit bitmap (that would match the saved PNG files). It’s 240,000 bytes. If we also assume the overheads are low – device ID, start address, and then just spit data, that’ll be 234K at 11K/sec which will be a little over 21 seconds to send a full display, with interrupts disabled the entire time (on a Pi). Running at my 400kHz rate, it’ll be a quarter of that, which is still an appreciable five seconds. As such, SPI (which is full duplex and can negotiate device transfer speeds up in the MHz range) is probably doing to be a better bet for anything larger than the tiniest e-ink displays. |