20-151-0178 Rabbit Semiconductor, 20-151-0178 Datasheet - Page 69

• Manufacturer Part Number: 20-151-0178
• Description: CABLE CONVERTER RS-232 TO USB
• Manufacturer: Rabbit Semiconductor

Specifications of 20-151-0178

• Accessory Type: USB to RS232 Adapter
• Product: Microcontroller Accessories
• For Use With/related Products: Rabbit-based Boards
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 20-151-0178; 316-1181

The sampling precision is the number of gradations possible for each sample point. Each time a sample is
taken, the sampling precision determines the digital value that is assigned. For example, if the precision is
10 the software can assign a sample one of 10 discrete numbers. By increasing the sampling precision, just
like with the sampling rate, you can make the sample points more closely resemble the curved line of the
analog signal.
As of the date of this manual, a really good description of sampling rate and precision (among other
things) can be found at:
www.howstuffworks.com/analog-digital3.htm
5.7 ADCs
To measure the analog input signal, the ramp-compare ADC circuits uses the ramp generator on the Pow-
erCore module. The ramp generator produces a saw-tooth signal that ramps up, then quickly falls to zero.
The input capture timer starts counting when the ramping up starts. When the ramp voltage matches the
analog input signal, a comparator fires, and the timer's value is recorded.
The RAMP_OUT pin is the output from the core module’s ramp generator.
The calibration of the ramp is tied to an onboard 2.5 V voltage reference. The 400 Hz ramp has a linear
rise time from 0 to 3.1 V of approximately 1.9 ms, and ramps down in approximately 0.45 ms. (The ramp
actually starts at a slightly negative voltage of approximately -0.05 V.) The ramp output has a linearity of
about 0.1%.
For more information on the ramp generator, see the
.
PowerCore FLEX User’s Manual
www.rabbit.com
RabbitFLEX User’s Manual
63