There are several analog pins available on OS board. For example, on OpenSprinkler 2.3 (AC), the available ones are A05, A06 and A07. The pins are all located at the top edge of the PCB. When referencing the pins in the source code, you can directly use the pin index (e.g. analogRead(5)) or use macro defined pin name (analogRead(A5)). Because the microcontroller runs at 3.3V VCC, the analog pins accept any signal between 0 to 3.3V.