I really like the neat little OLED displays. They are crisp and draw only some miliamps. Cheap OLED display have a resolution 128x32 that's enough for about 4 lines and 20 characters.

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

Code page 850

OLED and I2C Words

oled-emit works like the standard word emit. It blocks the calling thread, as long as the character is not written to the OLED display (less than 300 us for a 6x8 character and 400 kHz I2C). Horizontal (x) position is in pixel (0 to 127), 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.

oled-emit    ( Char -- )        Emits a character (writes a character to the OLED display)
oled-emit?   ( -- Flag )        OLED ready to get a character (I2C not busy)

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

oledpos!     ( x y -- )         Set OLED cursor position, 
                                x (column) horizontal position, max. 127  
                                y (row) vertical position (a line consists of 8 pixels), max. 3 for 128x32 or 7 for 128x64 displays.
oledpos@     (  -- x y )        Get the current OLED cursor position
oledcmd      ( c-addr -- )      Send command to the OLED controller SSD1306. First byte contains the length of the command.
oledclr      (  --  )           Clears the OLED display, sets the cursor to 0, 0
oledfont     ( u --  )          Select the font, u: 0 6x8, 1 8x8, 2 8X16 , 3 12X16
oledcolumn!  ( u -- )           Write a column (8 pixels) to the current position. Increment position. Bit 0 on top
oledcolumn@  ( -- u )           Read a column (8 pixels) from the current position

I2Cdev       ( u -- )           Sets the 7-bit I2C address
I2Cput       ( c-addr u -- )    c-addr buffer address for the message with lengh u to send
I2Cget       ( c-addr u -- )    c-addr buffer address for the message to receive
I2Cputget    ( a1 u1 a2 u2 -- ) a1 buffer address for the message to send, a2 buffer address for the message to receive

>oled        ( -- addr1 addr2 ) redirect to oled *)
>term        ( addr1 addr2 -- ) terminate redirection *)

*) part of redirection.fs

Usage

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

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

or even simpler

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

or on a command line

>oled .( Hallo Velo!) >term

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

: clock (  -- )
  oledclr
  3 oledfont
  -1 -1 -1 alarm!  \ set an alarm every second
  begin
    wait-alarm     \ wait a second
    0 0 oledpos!
    >oled .time >term
  key? until
  key drop
;

To change the display type you have to edit the oled.h and rebuild the project:

#define OLED_4PIN_128X32	0		// the cheap one with 4 pins, Adafruit Raspberry Pi #3527
#define	OLED_BONNET_128X64	1		// Adafruit Bonnet for Raspberry Pi #3531
#define OLED_FEATHER_128X32	2		// Adafruit FeatherWing #2900
#define OLED_FEATHER_128X64	3		// Adafruit FeatherWing #4650
#define OLED_OCTOPUS_128X64	4		// Octopus PIS-1277

#define OLED_LANDSCAPE		0
#define	OLED_PORTRAIT		1

// configure your OLED type
#define OLED_DISPLAY_TYPE	OLED_OCTOPUS_128X64
#define	OLED_ORIENTATION	OLED_LANDSCAPE

Links

SSD1306 Driver

Driver SW

• U8g2 https://github.com/olikraus/
• STM32 Graphical User Interface TOUCHGFX https://www.st.com/content/st_com/en/stm32-graphic-user-interface.html
• https://lexus2k.github.io/ssd1306/ https://github.com/lexus2k/ssd1306
• https://github.com/bitbank2/ss_oled
• SSD1306xLED https://git.x2software.net/pub/GameCounter/-/tree/master/Source/lib/ssd1306xled

Other OLEDs with SSD1306

• OLED B click 96x39 mono https://www.mikroe.com/oled-b-click, SSD1306
  • I2C address 60 / 0x3c or SPI
  • Manual SSD1306
  • https://learn.adafruit.com/adafruit-pioled-128x32-mini-oled-for-raspberry-pi
  • Manual SSD1351
    • Idles at low CPOL=0 hspi1.Init.CLKPolarity = SPI_POLARITY_LOW
    • CPHA=0 hspi1.Init.CLKPhase = SPI_PHASE_1EDGE

• Adafruit 128x64 Bonnet
  • https://learn.adafruit.com/adafruit-128x64-oled-bonnet-for-raspberry-pi/overview
  • https://pinout.xyz/pinout/i2c#

• Adafruit FeatherWing 128x64 OLED
  • https://learn.adafruit.com/adafruit-128x64-oled-featherwing

• Adafruit FeatherWing 128x32 OLED
  • https://www.adafruit.com/product/2900
  • Schematics https://learn.adafruit.com/assets/71319
  • D/C pin is not available -> data read is not possible

• https://www.lcd-module.de/fileadmin/pdf/grafik/oledm128-6.pdf

• Octopus
  • https://www.distrelec.ch/de/octopus-128x64-oled-display-pi-supply-pis-1277/p/30163414

SH1107 Driver

Slave address bit (SA0), D/C pin acts as SA0.

• SH1107 Datasheet
• https://www.displayfuture.com/Display/datasheet/controller/SH1107.pdf
• https://github.com/adafruit/Adafruit_CircuitPython_DisplayIO_SH1107/blob/main/adafruit_displayio_sh1107.py

FeatherWing 128x64 OLED

• https://www.adafruit.com/product/4650
• Schematics https://learn.adafruit.com/assets/94578
• I2C address selector D11 (JP3.6). 0 command, 1 data