Скачать или смотреть SSD1306 OLED brightness and dimming to (very) low levels

Read here first to understand what is going on.
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Displays do not flicker to naked eye (except the last, very dim setting).

The SSD1306 has a 256 level brightness setting (accessible via 81h register) but its effect is somewhat limited if you using jellybean modules from China.

Maximum brightness achieved easily but if you want to dim it, you can't dim it to low levels. "Precharge period" and "VCOMH deselect(sic) level" registers and to a limited extent charge pump register can be used for this.

What happens if you modify these registers can be seen in this video.

Disabling charge pump for achieving very low brightness levels is undocumented and unsupported feature which I found by accident. As you can see in video, only SPI display can work while charge pump disabled. I2C display simply display nothing, therefore charge pump disabling method is not usable on I2C display.

Left display connected via SPI, right display driven via I2C.
Hello world and 333°C is placeholder text.
The bottom line is important.

First value is Precharge (D9h)
Second value is VCOMH (DBh)
[DEF] means default suggested settings.
br = Brightness (81h)
CHGPMP OFF = Charge pump off (via writing 10h to 8Dh, to enable simply write 14h to same address)