From your downloads, open the example labeled as Example1-ReadButtons_WriteLEDs.ino. This example reads a switch and writes to the non-addressable LED using the PCA9554 I/O I 2 C Expander. For users ...

Obviously this wont be as idiot-proof as digitalWrite () is, but we think you can handle it. Our second tip is for a set of OLED displays from 4dsystems sold as Arduino Shields.

Using digitalWrite(pin, 0b10) sets the pin high as expected unless it is preceded by a digitalWrite(pin, 0b100), in which case writing 0b10 actually sets the pin low. Subsequent writes (including ...