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Month : 2078 UsersAnalog to Digital Conversion with C
Kamis, 21 Mei 2009 22:14:10 - oleh : juragan
To be able to implement analog to digital conversion using the ADC0804LCN 8-bit A/D converter. You will design a circuit and program the chip so that when an analog signal is given as input, the equivalent digital voltage is displayed on an LCD display. Thus, in effect, your circuit should function like a simple voltmeter.
Click Here to get the Schematic
Description:
The ability to convert analog
signals to digital and vice-versa is very important in signal
processing. The objective of an A/D converter is to determine the
output digital word corresponding to an analog input signal.
The Datasheet for ADC0804LCN
shows the pinout and a typical application schematic. The A/D converter
operates on the successive approximation principle. Analog switches are
closed sequentially by successive-approximation logic until the analog
differential input volatge[Vin(+) - Vin(-)] matches a voltage derived
from a tapped resistor string across the reference voltage.
The normal operation proceeds
as follows. On the high-to-low transition of the WR input, the internal
SAR latches and the shift-register stages are reset, and the INTR
output will be set high. As long as the CS input and WR input remain
low, the A/D will remain in a reset state. Conversion will start from 1
to 8 clock periods after at least one of these inputs makes a
low-to-high transition. After the requisite number of clock pulses to
complete the conversion, the INTR pin will make a high-to-low
transition. This can be used to interrupt a processor, or otherwise
signal the availability of a new conversion. A RD operation(with CS
low) will clear the INTR line high again. The device may be operated in
the free-running mode by connecting INTR to the WR input with CS=0.
Since this is an 8-bit A/D
converter, a voltage from 0-5V. O will be repersented as 0000 0000 (0
in decimal) and 5V is represented as 1111 1111 (256 in decimal). To
convert a value X volts to decimal, use the following formula: (X *
5.0)/256
To get a better resolution,
and display the vlaue as a floating point number, you can multiply the
numerator by a factor of 100, 1000 etc. and then print the voltage
accordingly.
Get the source code in Download Sections.....
( ADC0804C ziped file )
