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1300 Henley Court

Pullman, WA 99163

509.334.6306

www.digilentinc.com

Analog Shield Reference Manual

Revised June 5, 2014

Author: William Esposito

This document was edited and adapted for MPIDE by Digilent. The original document was prepared by

William Esposito at Stanford.

Overview

The Analog Shield offers a high fidelity and easy way to connect your Arduino™ or chipKIT™ to analog circuits. In

order to do this, the Digilent Analog Shield* provides:

In addition to providing many of the features available on other prototyping or breadboard shields, this shield

provides substantially more sensitive inputs and outputs than the Arduino Uno™ or the chipKIT UNO32™, as well

as providing the bipolar inputs and power supplies needed to drive many useful analog circuits.

The Analog Shield communicates with the Arduino using the SPI communication protocol. The Analog-to-Digital

input converter (ADC) and Digital-to-Analog output converter (DAC) both use the standard Arduino form factor SPI

bus pins and use independent chip selects.

* The Analog Shield was developed in cooperation with Texas Instruments® and the Kovacs / Giovangrandi lab at

Stanford University.

Figure 1. The Analog Shield.

•

4 Channel, 16 bit 100 ks/s SAR ADC.

• 4 Channel 16 bit 100 ks/s string DAC.

• Variable +/-7.5V Supply.

• Fixed +/-5V Supply.

• A small breadboard.

• Software read and write to the ADC/DAC with a

single line of C.

Other product and company names mentioned may be trademarks of their respective owners.

Page 1 of 5

Summary of content (5 pages)

PAGE 1
300 Henley Court Pullman, WA 99163 509.334.6306 www.digilentinc.com Analog Shield Reference Manual Revised June 5, 2014 Author: William Esposito This document was edited and adapted for MPIDE by Digilent. The original document was prepared by William Esposito at Stanford. Overview The Analog Shield offers a high fidelity and easy way to connect your Arduino™ or chipKIT™ to analog circuits. In order to do this, the Digilent Analog Shield* provides: • • • • • • 4 Channel, 16 bit 100 ks/s SAR ADC.
PAGE 2
Analog Shield: Introduction 1 Applications The Analog Shield allows better resolution for smaller and more sensitive signals that cannot reliably be recorded or generated using the standard pins on the Arduino. A few demos using the Analog Shield have been developed: - Sine wave / function generator (using direct digital synthesis). FFT spectrum analyzer. Polyphonic Music generation. 4-channel low bandwidth oscilloscope. Lissajou diagram generator. XY-Analog scope display driver.
PAGE 3
Analog Shield: Introduction 2. Digital to Analog Converter (DAC) Header The 2x4 header has the four DAC channels and four pins for the common ground on the board. The 4 ground pins are on the outside row of the header, while the 4 DAC channels are on the inner row of the header. The DAC modifies the analog signal produced from an Arduino or chipKIT. The standard Arduino/chipKIT analogWrite() function produces a pulse-width modulated (PWM) square wave that approximates the desired overall value over time.
PAGE 4
Analog Shield: Introduction To sample one of the analog input channels, use the function below. read() returns the voltage read on the channel. The voltage is returned in a binary representation from 0 to 65535 for -5V to 5V. unsigned int read(int channel, bool mode = false); To read from channel 0 (without differential mode) the syntax will look like this: unsigned int data; data = analog.read(0); This method samples the selected analog input. ‘Mode’ is an optional parameter.
PAGE 5
Analog Shield: Introduction To write multiple values to channels 0, 1, and 2 and have them update at the same: unsigned int data0 = 65535; unsigned int data1 = 256; unsigned int data2 = 0; analog.write(data0, data1, data2, true); Simultaneously updating methods are useful for higher speed applications where a small delay between channel outputs will produce unwanted signals or timing issues.