Ray over at rayshobby.net has just announced OpenSprinkler Pi v1.2:
Hi, this is a new product post for OpenSprinkler Pi (OSPi) v1.2. Since its original release, OSPi has become a very popular product. This version is a minor revision. The main change compared to version 1.1 is the addition of a PCF8591T 8-bit A/D D/A converter, which provides four independent 8-bit analog input pins, and one 8-bit analog output pin. The reason this has been added is that Raspberry Pi (RPi)’s GPIO pins do not have built-in ADC capability. In order to interface with analog sensors (such as soil moisture sensor, light sensor etc.), you would need an ADC unit. The addition of the PCF8591T chip allows OSPi to provide on-board analog inputs as well as output. This makes it more convenient for your prototyping need. Other than this, the rest of the circuit is pretty much the same as before, with 24V AC to 5V DC switching regulator (based on LM2596S), DS1307 RTC and backup battery, 74HC595 shift register and triacs.