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FPGA eink controller

ice40 FPGA based custom board to control eink display

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I started this project two years ago but lost interest last year after being stuck with the custom board. I since got it working, and will share my findings.

The idea is to control an old broken kindle 3 eink display with a FPGA. I started looking at http://essentialscrap.com/eink/waveforms.html and http://spritesmods.com/?art=einkdisplay since eink constructor is so secretive that you can't find any information. I got some success with a stm32f4 microcontroller but was disapointed by the poor performance (low refresh, black and white only). So I decided to do something better using an FPGA and some memory, I started with the ice40 Olimex board https://www.olimex.com/Products/FPGA/iCE40/iCE40HX1K-EVB/open-source-hardware.

Essential scrap website provide information about power driving of theses screen, but I was more interested in the signal driving, so I choose to use the TI TPS65185 IC http://www.ti.com/product/TPS65185 which manage everything (special thanks to @Arthur Admiraal for his design https://hackaday.io/project/7153-squidpad which I partially reused).

I used ICE40 because of the open-source toolchain available http://www.clifford.at/icestorm/

The memory permit to include a framebuffer, my Verilog implement a small SPI interface to communicate with the controller.

To simplify the development, I finally created my own little tool https://hackaday.io/project/14864-ifusb

The board is specificaly made for Kindle 3 display (ED060SC7), but should works with some other display from this generation (ED060SCE found in Kobo) which are 6" 800x600 16 colors.

Hardest part was to implement "waveform" which permit to make smooth and fast transition between screen refresh.

  • 1 × TPS65185 Power management IC
  • 1 × ICE40HX1K Logic ICs / Programmable Logic: FPGAs
  • 1 × K6R4016V1DND SRAM

  • Waveforms binary extract

    Julien5 days ago 0 comments

    In the Kindle 3 screen, the waveform is actually integrated into an SPI flash in the ribbon cable. In others e-reader, this can generaly be found in the firmware. E-Ink (PVI) created his own format, supported by custom controller, and some dedicated Epson chip. I think these controllers are obsoleted since CPU manufacturers does integrate the controller directly. Actually the main (only?) manufacturer which provide CPU supporting eink screen is Freescale (imx6 solo) and they created their format as well.

    I did not integrate the SPI signal out of the ribbon, but somebody already dumped the data, so I used that for working on an "extractor" to convert this data for the FPGA. As the whole technology, there is very few information about this PVI format. You can find some information in linux kernel (about the header of the binary), the rest is mostly guess : I'm not completely sure of the dumper yet, but the data extrated does give some correct results.

    References

  • Ebook reader test video

    Julien04/15/2017 at 17:14 0 comments

    Test with a homemade WIP epub reader, using ifusb interface ~ 1 fps

  • Waveforms table introduction

    Julien04/14/2017 at 16:14 1 comment

    With eink display, you cannot just send "set pixel black", "set pixel white" or "set pixel grey", the brightness of display depend on a sequence of voltage applied for a certain time on pixel.

    The table found in "Source driver" section on Essential Scrap site is incomplete, when you send 0b10, you do not actually set pixel white, you apply a voltage to set the pixel lighter, and 0b01 to set the pixel darker. It is why in his implementation, Petteri must apply multiple times the value to obtain the wanted color and apply the voltage longer than the screen can achieve. This approch will works, but the problem is it will be pretty slow when you want to update the screen.

    To get around that and get better result, eink manufacturer introduce what they call "waveforms table". This table describes the transition you must apply to obtain the faster results to go from one color to another.

    An example if you want to go from white to black, they can say that you will achieve that in 4 clock cycle in the form of 0b10 0b01 0b01 0b01, to go from grey to darker grey, the table can be something like 0b01 0b01 0b10 0b01, etc (it is an example, in general it is about 20 or 40 cycles).

    These waveforms are very difficult to obtain, since each eink display will have his own table, and the table will depend on temperature as well ! It is why I took some times to reverse engineering E-Ink (PVI) and Freescale binary format to extract some of these table to use them in the FPGA.

    Note there is multiple tables which correspond to different usage optimization : black and white, 2-bit/4 colors, 4-bit/16 colors (more on that later).

    Finally, this technique give really fast results, but after some times, you will see some "ghosting", some pixel from previous images are lighter or darker than they should, so a complete refresh is needed (see the "Page refresh" config in your kindle : you can set how regulary your should apply this full refresh).

    Sources:

    Petteri Aimonen's essential scrap waveform reverse engineering: http://essentialscrap.com/eink/waveforms.html

    Petteri Aimonen's eink driver implementation : https://github.com/PetteriAimonen/ED060SC4_driver

    My utils to extract waveform from binary : https://github.com/julbouln/ice40_eink_controller/tree/master/utils

    Example 2-bit waveform for ED060SC7 : https://github.com/julbouln/ice40_eink_controller/blob/master/controller/waveform_gc4.hex

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Trevor Johansen Aase wrote 4 days ago point

What was the cost of parts on the PCB? I see the displays are only $25 on eBay so could be an inexpensive project to play with.

  Are you sure? yes | no

Julien wrote 4 days ago point

PCB itself cost $30 on OSHPark (x3). In quantity 1 on digikey : PMIC cost ~$4.5, FPGA ~$5, SRAM between $3 and $4, 100Mhz crystal $2, LDOs $2, Screen conn $2, Ext conn. $2, SPI flash $1, so with the passives count around ~$25 in components.

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Trevor Johansen Aase wrote 3 days ago point

Thanks! Not much at all. I may think about a new weather station/thermostat unit in future projects.

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oshpark wrote 5 days ago point

Nice to see this project on Hackaday blog :) http://hackaday.com/2017/04/20/e-ink-display-driven-diy/

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Julien wrote 5 days ago point

@repkid Yes, theoricaly these panel are very similar. I think power part will works unmodified. On the other side connector won't fit, so some modification of the schematics & layout are needed. Maybe verilog need to be modified as well, if I remember some signals are active low instead of active high or the opposite.

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repkid wrote 4 days ago point

Thanks for the reply, I will try to get it to work with the ED060SC4. Are you going to release more waveforms?

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Julien wrote 4 days ago point

You can generate the waveform with the utils I provide, but I'm still figuring a way to find original binary waveforms. I found the ED060SC7 searching Google ...

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Julien wrote 5 days ago point

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repkid wrote 5 days ago point

This looks amazing, can this also be used to drive the ED060SC4?

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BeagleBoard Foundation wrote 04/18/2017 at 01:56 point

Very exciting!  Check it out, @Michael Welling.  Maybe this would work with the new BeagleBone cape you are working on.

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oshpark wrote 04/18/2017 at 01:41 point

Amazing project!  Thanks for sharing all the details

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Julien wrote 04/14/2017 at 07:19 point

Hi @Brangor, I sourced all components from digikey.com and the PCB from OSHPark, you should be able to make it at home if you have some soldering skills. You will need hot air soldering station because of TPS65185 which is in QFN package (and it is easier for small 603 components). Schematics and layout for free version of Eagle CAD are available here : https://github.com/julbouln/ice40_eink_controller/tree/master/hardware

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Brangor wrote 04/14/2017 at 02:41 point

Where do you go to purchase these components, and could you just soldier them on yourself, or would you use a service for that?  I see the board listed here: https://oshpark.com/shared_projects/rBoQ8bop - how much work would it be to put the right components onto it? Would it be done by just following some of the blogs on eink controllers that you listed with essentialscrap and spritesmods?

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