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November 4, 2021 at 12:25 pm #71567
ESP8266’s technical documents are all listed here:
PCA9555 is a I2C device, for I2C device, because the data lines are pulled high by the microcontroller, and the slave devices only pull these data lines to ground, it’s ok to have a 3.3V microcontroller interfacing with a PC9555 powered by 5V. 3.3V is within the high logic range of PCA9555, so this works fine.