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Maxim > Design
support > App notes
> A/D and
D/A Conversion/Sampling Circuits > APP
4530
Maxim > Design support >
App notes
> Microcontrollers
> APP 4530

Sep 24, 2009

Keywords: MAX1393, ADC, PC based,
oscilloscope

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PDF format (124kB)

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REFERENCE DESIGN 4530

INCLUDES: Tested
circuit Schematic Board
available Description Software

Reference Design for a PC-Based Oscilloscope

By: Gordon
Lee

Abstract: This
article presents a reference design for a PC-based
oscilloscope. The MAX1393 ADC and MAX1396 EV (evaluation) kit
are featured. Schematics, software, and explanation of
software functions are all provided.

Introduction
This reference design provides everything
needed to implement an oscilloscope (Figure 1) based
around the MAX1396EVKIT
(reference design requires the MAX1396ETB ADC
to be replaced with the MAX1393ETB ADC) and
a PC. Included are schematics, Windows® software, and
microcontroller firmware. The example
firmware is a C program written and assembled specifically
for the MAXQ2000 using the
IAR Embedded Workbench®. Download
the free IAR Embedded Workbench for MAXQ® 1.13C, 4K KickStart
Edition.

Figure
1. The PC-based oscilloscope.

MAX1393 Overview
The MAX1393 is a 312.5ksps,
1-channel, true-differential, 12-bit SAR ADC. This reference
design uses the MAX1393 to capture the input wave
signals.

Hardware Overview
The MAX1396EVKIT consists of one
MAX1396 ADC (which will be replaced by a MAX1393 device for
this design); one MAXQ2000 microcontroller; all required
passive components; and a proven PCB
layout. The MAX1396EVKIT schematic is shown in Figure
2.

The MAX1393 is not present on the MAX1396EVKIT
board. Order a sample
of MAX1393ETB through Maxim's website and replace the
MAX1396ETB device on the board. Table 1 shows the
required jumper settings.

More
detailed image (PDF, 19kB)
Figure 2. MAX1396EVKIT
schematic.

Table 1. Jumper Settings

Jumper

Position

JU1

1-2

JU2

1-2

JU3

1-2

JU4

1-2

JU5

1-2

JU6

1-2

JU7

1-2

Firmware Overview
The example C program files in
AN4530-firmware.zip allow the MAXQ2000's SPI™ peripheral to
communicate with the MAX1393. The SPI
serial
clock is 5MHz when a 20MHz system clock is used for the
MAXQ2000. When the MAXQ2000 receives a command from the PC,
the microcontroller will start taking input signal data from
the MAX1393. After 512 sampled data are stored, the MAXQ2000
will send them back to the PC.

Windows Program Overview
Once the MAX1396EVKIT is
connected to the PC through a USB
cable,
the firmware waits for the commands from the Windows program,
shown in Figure 3. Press the Convert button to
receive the input signal's sampled data from the EV kit; data
will be displayed with a waveform (Figure 4). When the
mouse cursor is placed over the waveform area, the
corresponding Time and Voltage level will be
displayed at the top of the screen (Figure 5). All
other software functions are described in Table
2.

Figure
3. Windows program starts up for the MAX1393 reference
design.

Figure
4. Display waveform.

Figure
5. Time and voltage level are displayed at the
top.

Table 2. Software Functions

Button

Description

Vertically scales the waveform.

Horizontally scales the waveform.

Shifts the waveform horizontally.

Enter a value (in milliseconds) into the edit box
and press the Set button to set the starting time
at the left of the screen.

Enter a value (in milliseconds) into the edit box
and press the Set button to set the ending time
at the right of the screen.

Enter a value (in milliseconds) into the edit box
and press the Set button to set the sampling
time.

Enter a proper trigger-level value into this edit
box.

Click on one of the two radio buttons to choose
either rising-edge triggering or falling-edge
triggering.

Press this button to receive input-signal data from
the EV
kit board and display the waveform on the
screen.

Select this checkbox to receive continuous data from
the EV kit and continuous updates to the waveform on the
screen.

Press this button to redraw the waveform on the
screen.

Press this button to exit the
program.

IAR
Embedded Workbench is a registered trademark of IAR Systems
AB.

MAXQ is a registered trademark of Maxim
Integrated Products, Inc.

SPI is a trademark of Motorola, Inc.

Windows is a registered trademark and registered
service mark of Microsoft Corporation.

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Download,
PDF format (124kB)
APP 4530: Sep 24, 2009

AN4530, AN 4530, APP4530,
Appnote4530, Appnote 4530

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