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Re: 4.41 inch ePaper Display for the rPi

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On 6/19/2015 7:58 PM, Martin Gregorie wrote:
> On Fri, 19 Jun 2015 17:43:50 -0400, rickman wrote:
>
>> This points to another short coming in the ePaper info.  What is
>> different about the displays used in eReaders and the displays Pervasive
>> sells?
>>
> Might the Kobo use a faster, more capable controller?
>
> I wonder how much the update speed is affected by the transfer rate.

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.


> 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,

Why?  There are 120,000 pixels.  At 20 MHz the SPI can support 166 
updates per second.


> 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.

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.

-- 

Rick

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Re: 4.41 inch ePaper Display for the rPi Martin Gregorie <martin@address-in-sig.invalid> - 2015-06-18 22:39 +0000
  Re: 4.41 inch ePaper Display for the rPi Martin Gregorie <martin@address-in-sig.invalid> - 2015-06-19 19:10 +0000
    Re: 4.41 inch ePaper Display for the rPi rickman <gnuarm@gmail.com> - 2015-06-19 15:34 -0400
      Re: 4.41 inch ePaper Display for the rPi Martin Gregorie <martin@address-in-sig.invalid> - 2015-06-19 20:36 +0000
        Re: 4.41 inch ePaper Display for the rPi Martin Gregorie <martin@address-in-sig.invalid> - 2015-06-19 23:22 +0000
        Re: 4.41 inch ePaper Display for the rPi Martin Gregorie <martin@address-in-sig.invalid> - 2015-06-19 23:58 +0000
          Re: 4.41 inch ePaper Display for the rPi hamilton <hamilton@nothere.com> - 2015-06-19 18:25 -0600
          Re: 4.41 inch ePaper Display for the rPi rickman <gnuarm@gmail.com> - 2015-06-19 22:44 -0400
            Re: 4.41 inch ePaper Display for the rPi rickman <gnuarm@gmail.com> - 2015-06-20 13:29 -0400
        Re: 4.41 inch ePaper Display for the rPi cl@isbd.net - 2015-07-29 10:26 +0100
          Re: 4.41 inch ePaper Display for the rPi cl@isbd.net - 2015-07-29 21:21 +0100
            Re: 4.41 inch ePaper Display for the rPi rickman <gnuarm@gmail.com> - 2015-07-29 17:18 -0400
              Re: 4.41 inch ePaper Display for the rPi cl@isbd.net - 2015-07-30 10:23 +0100
                Re: 4.41 inch ePaper Display for the rPi Rob <nomail@example.com> - 2015-07-30 11:14 +0000
                Re: 4.41 inch ePaper Display for the rPi Dom <domafp@blueyonder.co.uk> - 2015-07-30 12:55 +0100
                Re: 4.41 inch ePaper Display for the rPi cl@isbd.net - 2015-07-30 13:15 +0100
  Re: 4.41 inch ePaper Display for the rPi Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-06-19 20:27 +0100
    Re: 4.41 inch ePaper Display for the rPi rickman <gnuarm@gmail.com> - 2015-06-19 15:57 -0400
  Re: 4.41 inch ePaper Display for the rPi Martin Gregorie <martin@address-in-sig.invalid> - 2015-06-19 19:31 +0000

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