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adafruit / Adafruit_SSD1306

Arduino library for SSD1306 monochrome 128x64 and 128x32 OLEDs
http://www.adafruit.com/category/63_98
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Setup SPI in mode 3 #191

Closed TobleMiner closed 3 years ago

TobleMiner commented 3 years ago

Previously the SPI was operated in mode 0. However the 4-wire serial timing diagrams in the SSD1306 datasheet show that CPOL must be 1, because clock is high at idle (page 52). This commit changes the SPI to operate in mode 3 where CPOL is 1, placing the clock in high state when idle.

Datasheet: https://cdn-shop.adafruit.com/datasheets/SSD1306.pdf

Relevant diagram: ssd1306_4wire_serial_sequence

As far as i'm aware this should not break compatibility with any SSD1306 based displays. Due to the seemingly large amount of SSD1306 clones I'd appreciate third party testing. Especially since I do not have a single display to test this change on at the moment. I did only notice the disparity between spec and implementation while developing a SSD1306 emulator, looking at logic analyzer captures.

TobleMiner commented 3 years ago

According to the second diagram on page 52 and various implementations of SSD1306 interfaces the CPOL seems to be irrelevant. Thus I'm closing this PR for now. Please feel free to reopen if you are having issues with mode 0.