Driver epd.c, fonts from https://www.mikrocontroller.net/topic/54860.

Code page 850

EPD and SPI Words

epd-emit works like the standard word emit. It blocks the calling thread, as long as the character is not written to the EPD display. Horizontal (x) position is in pixel (0 to 249), vertical position (y) is in lines, a line consists of 8 pixels. 0, 0 is upper left corner. Larger fonts takes more than one line.

epd-emit      ( c -- )      Emits a character (writes a character to the EPD framebuffer)
epd-emit?     ( -- ? )      EPD ready to get a character (SPI not busy)

hook-emit     ( -- a )      Hooks for redirecting terminal IO on the fly
hook-emit?    ( -- a )    

epdpos!       ( x y -- )    Set EPD cursor position, 
                              x horizontal position, pixel resolution, e.g. 0 to 249 for 250x122 displays.
                              y vertical position (line), max. 15 for  250x122 displays.
epdpos@       ( -- x y )    Get the current EPD cursor position
epdclr        ( -- )        Clears the EPD display, sets the cursor to 0, 0
epdfont       ( u -- )      Select the font, u: 0 6x8, 1 8x8, 2 8X16 , 3 12X16

epdupdate     ( --  )       Update the display (copy the framebuffer to the display)
epdstartpart  ( --  )       Start the partial update for the EPD display
epdupdatepart ( -- )        Update part of the EPD display
epdcmd        ( a -- )      Send command to the EPD controller SSD1680. First byte contains the length of the command.

epdsleep      ( -- )        enter deep sleep mode
epdwakeup     ( -- )        wake up EPD

epdpixel!     ( ? x y -- )  not implemented yet
epdpixel@     ( x y -- ? )  not implemented yet
epdcolumn!    ( u -- )      Write a column (8 pixels) to the current position. Increment position. Bit 0 on top
epdcolumn@    ( -- u )      Read a column (8 pixels) from the current position

>epd          ( -- a1 a2 )  redirect to EPD *)
>term         ( a1 a2 -- )  terminate redirection *)

*) part of redirection.fs

Usage

It is easy to redirect the terminal output to the EPD display, to use the string formatting words.

: epd-hallo (  -- )
  hook-emit @              \ save emit hook
  ['] epd-emit hook-emit !  \ redirect terminal to epd-emit
  ." Hallo Velo! " cr
  ." ciao"
  hook-emit !         \ restore old hook
  epdupdate
;

or even simpler

: epd-hallo (  -- )
  >epd         \ redirect terminal to epd-emit
    ." Hallo Velo! " cr
    ." ciao" 
  >term         \ terminate redirection
  epdupdate
;

or on a command line

>epd .( Hallo Velo!) >term 
epdupdate

show date and time on EPD (see CmsisRtos#How_to_use_Tasks for a background task).

: clock (  -- )
  epdclr  
  3 epdfont
  >epd .time >term
  epdupdate
\  2000 osdelay drop
  -1 -1 -1 alarm!  \ set an alarm every second
  begin
    wait-alarm     \ wait a second
    0 0 epdpos!
    epdstartpart
      >epd .time >term
    epdupdatepart
  key? until
  key drop
;

Adafruit EInk Feather Board

• Adafruit 2.13" Monochrome eInk / ePaper Display FeatherWing - 250x122 Monochrome with SSD1680 4195
• Adafruit eInk Feather Friend with 32KB SRAM 4446

The partial and fast update for the Adafruit #4195 is not working for me. But the very similar EPD YMS122250-0213AAAMFGN from DISPLAY LC or YES Optolectronics use the red color memory for the partial update, about 300 ms and no flickering at all. Is Adafruit using the GDEY0213B74 (or GDEY0213B72, GDEY0213B73) https://www.good-display.com/product/391.html for its display?

Schematics

Driver, Links

SSD1680 Driver

One byte display memory contains 8 pixels. Logical 0 is black, logical 1 is white. Most significant bit is first pixel.

250 x 122

Portrait

• 122 columns * 31 1/4 rows
• resolution 122 * 250
• 20 * 31 chars (8*6 chars)

Landscape

• 250 columns * 15 1/4 rows
• resolution 250 * 122
• 41 * 15 chars (8*6 chars)

Driver SW

• https://www.solomon-systech.com/product/ssd1680-80a/
• Datasheet
• Adafruit EPD Library

• https://www.good-display.com/news/134.html partial update

Other EPDs with SSD1680

• 2.9" E-Ink Grayscale FeatherWing #4777 https://www.adafruit.com/product/4777
• 2.13" E-Ink Monochrome FeatherWing #4195 250x122 Pixel https://www.adafruit.com/product/4195 (pinouts
• E-Ink Feather Friend #4446 https://www.adafruit.com/product/4446 (schematics)

Graphics File Formats

• Portable BitMap, binary P4 and ASCII P1 variant
  • https://en.wikipedia.org/wiki/Netpbm#File_formats
  • http://netpbm.sourceforge.net/doc/pbm.html
• X PixMap (XPM), usable in C-Files
  • https://en.wikipedia.org/wiki/X_PixMap
• X BitMap (XBM), plain text binary in C .h
  • upper left pixel in the bitmap represented by the low bit of the first byte in the array
  • https://en.wikipedia.org/wiki/X_BitMap

Portable BitMap, binary P4

• https://en.wikipedia.org/wiki/Netpbm#File_formats
• http://netpbm.sourceforge.net/doc/pbm.html

.pbm

P1
# This is an example bitmap of the letter "J"
6 10
0 0 0 0 1 0
0 0 0 0 1 0
0 0 0 0 1 0
0 0 0 0 1 0
0 0 0 0 1 0
0 0 0 0 1 0
1 0 0 0 1 0
0 1 1 1 0 0
0 0 0 0 0 0
0 0 0 0 0 0

P4
# This is an example bitmap of the letter "J"
6 10
08080808080888700000

ImageMagick

ImageMagick

$ convert image.png -rotate -90 -flip image.pbm

$ convert image.png -rotate 90 -flop image.xbm

$ convert image -colorspace gray -threshold 10% -type bilevel result

$ convert image -separate -monochrome result

$ convert image.png -separate -monochrome -rotate 90 -flop -negate image.xbm

convert image36 -shave 2x2 image32