Programmable Switching Clock with Sensor Inputs

Using a handful of external components our AT89S8252 Flash Micro board can be turned into a switching clock with sensor inputs and four switched outputs. The author demonstrates the programming of various inputs and outputs, aiming to control, for example, a small irrigation system.The peripheral circuitry to add to theFlash Micro board consists of a (telephone) keypad connected as a matrix across port lines P1.0 through P1.6, a real-time clock type DS1302 (from Dallas Semiconductor) whose 3-wire bus is hooked up to port lines P2.0, P2.1 and P2.2, and, finally, a standard LC display with 2 rows of 16 characters. Thanks to the abundance of port lines on the 89S8252 controller, the LCD can be operated in 8-bit mode when connected to P0.0 through P0.7.