Project 3 : Analog to Digital Conversion MAE 5483

Introduction This project’s purpose is to become familiar with analog to digital conversion on a PIC micro-controller. Four programs demonstrate: assembly timing, A/D conversions, A/D conversion rates, and RC circuit time constants. The micro-controller is a 28 pin DIP PIC16F876 manufactured by Microchip. The PIC voltage input is +5 volts DC via a μA7805 dc/dc voltage regulator. The compiler is the CCS C compiler (v. 3.207) for 14 bit PIC chips. C compilation occurs on a x86 based PC. Data transfer between the PIC and the PC is through a 9 pin serial cable. All programming and experiments were performed by Charles O’Neill. Figure 1 shows the circuit schematic for this project. LED is active low and connected to pins B7. For all PIC inputs, 470 Ohm resistors restrict the current to a maximum of 10 mA. A 5K potentiometer is used to provide 0–5 Volt source into pin A0 of the A/D converter. Program 3 uses an RC circuit connected to pin B4 —variable resistor and capacitor components were used. The external