SSD1306 OLED (72x40) I2C display from scratch

[flotulopex]

...credits are all for Richard

[richard]

something to consider about fonts
it looks like you want 40x22 size font
a pic16 has a flash word size of 14 bits therefore a font that size
will take if encoded horizontally by row take 2x40 words per chr
it will take 3x22 words if encoded vertically by column a reasonable saving.

one of the benefits of the ssd1306 controller is that it can address its graphics ram either way with ease

[flotulopex]

Richard,

I'm still trying to understand your previous post but just for now, there's a question burning my mind: how do I address the display pixel by pixel?

[richard]

you cannot, the smallest element is 1 byte ie one column[page] of 8 rows

[flotulopex]

you cannot

Right, so you are talking about using data in a more efficient way using the vertical display mode as described in figure 10-4, correct?

[richard]

yes , aligning the font data packing with the ssd1306's memory page layout is more efficient usage of the 14 bit width of the flash memory
while it will still need some clever manipulation to unpack it into a 8 bit data stream

[flotulopex]

Okay, found!

[flotulopex]

For any reason, my OLED module won't start up once out of ten or twenty times.

I have no clue why.

I change OLED modules (I have five and do all the same), changes breadboards, changed µC... I don't know what to try next.

Any idea?

' OLED-72x40_16F18446

' ====== FUSES =====================================================================================
' External oscillator
#CONFIG
    __config _CONFIG1, _FCMEN_OFF & _CSWEN_OFF & _CLKOUTEN_OFF & _RSTOSC_EXT1X & _FEXTOSC_HS
    __config _CONFIG2, _MCLRE_OFF & _PWRTS_PWRT_64 & _LPBOREN_OFF & _BOREN_OFF & _BORV_LO & _ZCD_OFF & _PPS1WAY_OFF
    __config _CONFIG3, _WDTCPS_WDTCPS_31 & _WDTE_SWDTEN & _WDTCWS_WDTCWS_7 & _WDTCCS_LFINTOSC
    __config _CONFIG4, _BBSIZE_BB512 & _BBEN_OFF & _SAFEN_OFF & _WRTAPP_OFF & _WRTB_OFF & _WRTC_OFF & _WRTD_OFF & _WRTSAF_OFF & _LVP_OFF
    __config _CONFIG5, _CP_OFF
#ENDCONFIG

@ ERRORLEVEL -306
@ ERRORLEVEL -202

' ====== REGISTERS =================================================================================
ANSELB  = %00000000

' ====== DEFINES ===================================================================================
DEFINE OSC 32
DEFINE NO_CLRWDT 1   ' don't waste cycles clearing WDT  
DEFINE HSER_CLOERR 1 ' automatic clear overrun error 
DEFINE I2C_SLOW 1    ' if >8MHz

' ====== VARIABLES =================================================================================
SDA         VAR PORTB.5 ' I2C Clock
SCL         VAR PORTB.6 ' I2C Data

' SSD1306 OLED 72x40 module (has built-in 10k pull-up on SDA/SCL)
I2CDevice   CON $78
Page        VAR BYTE ' OLED's Pages 0..4

' ====== SSD1306 I2C OLED initialization ===========================================================
PAUSE 500 ' let display settle

' Initializing command set
I2CWrite SDA,SCL,I2CDevice,[$00,$AE,$D5,$80,$A8,$3F,$D3,$00,$20,$00,$AD,$30,$8D,$14,$68,$A6,$A4,_
    $A1,$C8,$DA,$12,$81,$7F,$D9,$22,$DB,$40,$2E,$AF]
PAUSEUS 50    

' ====== PROGRAM STARTUP ===========================================================================
STARTUP:
    Gosub CLEAR_DISPLAY_FULL

' ====== MAIN PROGRAM ==============================================================================
MAIN:
    GOSUB SPLASH1
    PAUSE 2000
    GOSUB SPLASH2
    PAUSE 2000
    GOTO MAIN
END

' ====== CLEAR FULL DISPLAY ROUTINE ================================================================
CLEAR_DISPLAY_FULL:
    I2CWrite SDA,SCL,I2CDevice,[$00,$21,28,99,$22,0,4]
    FOR Page = 0 TO 4
        I2CWrite SDA,SCL,I2CDevice,[$40,_
            0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, _
            0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, _
            0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, _
            0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
    NEXT Page    
    RETURN

' ====== SPLASH SCREEN DISPLAY =====================================================================
SPLASH1:
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,252,252,252,60,28,28,28,56,248,248,240,192,0,0,0,252,252,252,0,0,0,0,192,240,248,120,60,28,28,28,28,60,248,248,240,192,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,255,255,255,56,56,56,56,60,31,31,15,3,0,0,0,255,255,255,0,0,0,62,255,255,255,128,0,0,0,0,0,0,192,192,192,192,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,15,15,15,0,0,0,0,0,0,0,0,0,0,0,0,15,15,15,0,0,0,0,1,3,7,15,14,14,12,14,14,15,15,7,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,240,252,252,140,140,204,252,120,0,0,0,96,96,32,32,224,224,0,0,192,224,224,32,32,96,64,0,0,192,236,108,0,128,192,224,96,32,96,96,64,0]
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,62,63,55,49,49,57,31,31,6,0,28,62,54,34,18,63,63,7,0,16,56,49,35,55,62,30,0,0,56,63,15,0,0,31,63,48,48,48,56,24,0,0]
    RETURN
    
SPLASH2:
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,128,128,192,192,0,0,0,0,128,192,192,192,192,192,128,0,0,192,192,192,192,192,192,0,0,128,128,192,192,0,0,0,0,128,192,64,192,128,0,0,0,0,0,0,0,192,192,192,0,0,0,0,0,0,0,192,192,192,0,0,0,128,192,192,192,192,192,128,0,0]
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,1,129,255,255,128,0,0,0,255,255,136,12,140,249,249,0,0,255,255,12,12,12,12,0,0,1,129,255,255,128,0,0,99,255,32,8,156,255,99,0,0,96,120,124,103,99,255,255,96,0,0,96,120,124,103,99,255,255,96,0,0,255,255,136,12,140,249,249,0,0]
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,1,1,1,1,1,1,0,0,0,1,1,1,1,1,0,0,0,1,1,0,0,0,0,0,0,1,1,1,1,1,1,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,1,1,0,0,0,0,1,1,1,1,1,0,0,0]
    I2CWrite SDA,SCL,I2CDevice,[$40,_
        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
    RETURN

[rsocor01]

Use a logical analyzer to see if the module responds to "Initializing command set" when it fails. If it doesn't respond you can try a longer pause "PAUSE 500 ' let display settle".

Check that you don't have any noise in the power lines or control lines.

[flotulopex]

Use a logical analyzer to see if the module responds to "Initializing command set" when it fails.

How would I do this?

BTW, I just noticed that the module won't start up again if the time between a shut off and switch on is below 2-3 secs. Anyway, it is strange.

So, if I leave the module unpowered for more than 5 seconds, it'll always restart.

Maybe this is something absolutely "normal".

[rsocor01]

Connect a logical analyzer to tx and rx. They are not expensive. Digikey has one for $20. You can see the ones and zeroes going to the module and coming back to the pic. If you don't use a logic analyzer, it is like shooting in the dark.

About that 2-3 seconds observation, it is very likely that it is a power issue. Maybe you have a large cap that is holding a charge.


https://www.digikey.com/en/products/...DgGxgOwgF0BfIA

[richard]

For any reason, my OLED module won't start up once out of ten or twenty times.


I have no clue why.

Since the module you are using has no provision made for the user to be able to reset it you are totally dependent on how the on board POR circuitry applies the reset signal. The board will have a very definite absolute minimum off period and minimum on time before a successful reset will occur. If you don't adhere to those times then its matters not what you code is trying to do the chip won't necessarily be receptive. If your code still does not work reliably after suitable POR conditions have been met then you code is incorrect. Simply resetting your pic is not enough.

The data sheet gives no clue re command execution time or even if i2c clock stretching is in play, anecdotally there is some support for a small delay after executing an $ae command being beneficial