lab9_f10 - University of Florida Department of Electrical...

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University of Florida EEL 4744 Dr. Gugel Department of Electrical and Computer Engineering Fall 2010 11/19/10 Page 1/2 Lab #9: A/D & D/A Conversion Purpose The purpose of this lab is to become familiar with Analog to Digital conversion (ADC) and Digital to Analog conversion (DAC) techniques and hardware. We will first use the F28335 DSP’s onboard A/D converter to build a simple voltage meter with the LCD display we added early in the semester. Next, we will add an external serial DAC device to play out waveforms stored in memory. The play back sampling rate will be controlled via a Timer or PWM/Event Capture interrupt and in essence we will be creating a simple digital sound synthesizer. Part I. Using an A/D to Create a Simple Multi-meter The first step in being prepared for this lab is to read the documentation associated with the DSP's onboard A/D converter in TI’s reference documentation. Upon completion of this preparation: 1. Connect a potentiometer to any open channel on the ADC found in the DSP. 2. In software, capture the analog voltage on the center tap of the pot and convert the 12 bit binary value to a voltage. 3. Display the voltage on your LCD in decimal mVolts as shown below: A/D Voltage = 1650 mV The voltage should have 50 mV accuracy and range from 0 to 3000 mV. 4. Repeat steps #2 & #3 in a loop forever. 5. You can use a look-up table for the calculation or a straight formula to come up with the raw value to decimal voltage conversion. The formula method is best and certainly easiest for those who will write their code in ‘C’. Note: You may use assembly or ‘C’ for this lab and can use polling or interrupt driven software. 6. Testing - Connect a small hand held multi-meter between the center tap Pot pin and ground. Monitor the voltage on the hand held meter with that shown on your LCD as you alter the voltage going to the ADC with the pot screw. Verify they
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lab9_f10 - University of Florida Department of Electrical...

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