26-12-2012, 04:28 PM
ADC Interfacing
ADC Interfacing.ppt (Size: 2.54 MB / Downloads: 39)
Analog-to-digital converter (ADC )
Need to have some means to convert them into digital signal so that computers can handle
Analog-to-digital converter (ADC) is a device which can convert analogue voltage to digital numbers so that microcontrollers can handle and process the data.
ADC are the most widely used devices for data acquisition
ADC has n-bit resolution, where n can be 8, 12, 16 or even 24 bits.
The higher-resolution ADC provides a smaller step size.
Step size is the smallest change that can be recognized by ADC.
ADC0804 Chip
CS
Active low input used to activate the ADC0804 chip.
RD (data enable)
Active low input used to get converted data out of the ADC0804 chip. When CS = 0, if a high-to-low pulse is applied to the RD pin, the 8-bit digital output shows up at the D0-D7 data pins.
WR (start conversion)
Active low input used to inform the ADC0804 to start the conversion process. If CS = 0 when WR makes a low-to-high transition, the ADC0804 starts converting the analog input value of Vin to an 8-bit digital number. When the data conversion is complete, the INTR pin is forced low by the ADC0804.
Signal control on ADC0804
Make CS = 0 and send a L-to-H pulse to pin WR to start the conversion.
Keep monitoring the INTR pin. If INTR is low, the conversion is finished and we can go to the next step. If INTR is high, keep polling until it goes low.
After the INTR has become low, we make CS = 0 and send a H-to-L pulse to the RD pin to get the data out of the ADC0804 IC chip.
Digital-to-Analog (DAC) Conversion
The digital-to-analog converter (DAC) is a device widely used to convert digital values to analog signals.
It does the reverse operation of an ADC
The resolution of DAC depends on the no. of binary bits input to it.
The common ones are 8, 10 and 12 bits.
An 8-input DAC provides 256 discrete voltages (or current) levels of output. (The 12-bit DAC gives 4096 discrete levels).