Using OLED expansion with other devices
Re: oled exp pinout
I've been trying to get an ESP8266 to see the OLED expansion using these pinouts with no luck. An i2c scan cannot see it, though it can see other SSD1306 displays without issue. I am only connecting one display at a time so address conflicts aren't the issue.
The OLED expansion is working fine with the Omega2 so I don't understand what the problem could be. Any advice?
And I just answered my own question... I found the following post which VERY helpfully mentions that pins 3 and 4 need to be shorted.
do not forget to remove the pin3-pin4 short circuitif you want to plug the Oled Expansion to any genuine Onion Omega Expansion
BoardHeader directly because Omega2(+) may be damaged if you set GPIO11 to Low.
There are I2C level shifters on the OLED Expansion.
Pin4 of the Expansion Header provides the voltage to the lower voltage section for those level shifters.
But pin4 of the Expansion Header is connected to GPIO11 on the Omega2(+) board.
So @Onion must set GPIO11 to High (~3.3V). It's a hidden simple hack that @Onion forgot to mention for example here.
You could find some further technical details here.