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. Larger fonts takes more than one line.

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

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

epdpos!      ( x y -- )         Set EPD cursor position, 
                                x horizontal position, for 6x8 font max. (250 / 6) -1, depends on the font's x size 
                                y vertical position (a line consists of 8 pixels), max. 14 for 255x122.
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)
epdpartial   ( x1 y1 x2 y2 -- ) Partial update the display
epdcmd       ( c-addr -- )      Send command to the EPD controller SSD1680. First byte contains the length of the command.

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

>epd         ( -- addr1 addr2 ) redirect to EPD
>term        ( addr1 addr2 -- ) terminate redirection

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"
  epdupdate
  hook-emit !         \ restore old hook
;

or even simpler

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

or on a command line

>epd .( Hallo Velo!) epdupdate >term 

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

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

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

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