DT7837

ARM Module for Embedded Applications
Overview
The DT7837 is a high accuracy dynamic signal acquisition
module for noise, vibration, and acoustic measurementswith an embedded Cortex-A8 600 MHz ARM processor.
Data from four, 24-bit, IEPE (ICP®) sensor input data
can be algorithmically processed in real time with theoptional use of a 24-bit stimulus D/A generator and theresults presented to a host for analysis.

Key Features

The DT7837 provides 4 IEPE input channels along with anembedded ARM processor for real-time processing andanalysis of sound and vibration measurements.

• Dynamic Signal Analyzer with embedded ARM• 4 IEPE channels, 24-bit resolution, up to• Micro SD-Card interface for measurement results

102.4 kS/s/ch simultaneous samplingand raw data

• Digital I/O (8 In/8 Out), General-Purpose Counter/• USB-host port for additional SSD hard disk, WirelessTimer, Measure Counter, Tachometer, and External
Digital (TTL) Trigger• High speed, 24-bit, stimulus analog output for
dynamic waveform generation• TI AM335x ARM Cortex-A8 MPU with 2 GB onboard
NAND Flash memory• Open source Linux computing platform using the TIAM335x SDK Essentials Version 7.0

LAN, or GSM communication stick• RS232 (3.3 V) serial interface to communicate withPLC• Ethernet and USB client for host communication• Numerous example programs included to get you up
and running quickly

Supported Operating Systems• LinuxThe DT7837 block diagram shows the base board (ARM block) with the TI AM335x ARM Cortex-A8 processor,
FPGA, memory and support peripherals as well as interfaces for a USB host and client, Ethernet, power, SD
card and digital I/O, counters and timers. The daughter board (I/O Block) has the A/D and D/A, and is mated tothe ARM Block through a connector.

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The DT7837 is a small two-board sandwich providing the ARM block, an industrialized BeagleBone Black derivative, and theI/O Block for A/D, D/A, and digital signals. The result is a high performance, real-time sound & vibration system for embedded
applications using Open Source LINUX.

The DT7837 is designed for embedded applications. The I/O block (top board) contains the analog I/O circuitry and the ARM
block (bottom board) houses the ARM processor, digital I/O circuitry, and the connectors for communicating with the hostcomputer and other devices.

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DT7837 Overview

Input Triggers

The DT7837 module is an open-source Linux computing
platform with a high-accuracy, dynamic signal analyzer
front-end, making it ideal for embedded applications that
require noise, vibration, and acoustic measurements. The
module is composed of two boards. The bottom board
contains the ARM block and the top board contains theI/O block. Users can embed the module into their own
enclosure and/or system.

The DT7837 module supports the following sources forstarting acquisition:• software trigger• external digital (TTL) positive or negative trigger• threshold trigger
Tachometer Input
The DT7837 supports a tachometer input signal with arange of ±30 V. The frequency or period between twoedges of the tachometer input signal can be measured
to calculate the rotational speed of the high leveltachometer input. The value can then be returned thevalue in the analog input data stream. The startingedge (either rising or falling) of the tachometer signal isprogrammable. An internal 12 MHz counter is used forthe measurement.

ARM Block
The ARM block of the DT7837 module uses the TI Sitara
AM3352 processor and its associated peripherals toprovide an open-source, single-board computer. TheDT7837 is designed for embedded applications. TheI/O block (top board) contains the analog I/O circuitry
and the ARM block (bottom board) houses the ARM
processor AM3352 supports many different interfaces,
many of which are shared on the configurable I/O pins.
In addition to the AM3352, the DT7837 module uses anembedded NAND flash and an FPGA.

Digital I/O Lines
The DT7837 module supports one digital input port,
consisting of 8 digital input lines and one digital output
port, consisting of 8 digital output lines. Users cansynchronously read all 8 digital input lines or write to all 8
digital output lines. Users can also return the value of thedigital input port in the analog input stream to correlate
digital input and other input measurements or update
the value of the digital output port in the analog outputstream.

Analog Input Channels
The DT7837 provides four analog input channels. IEPE
sensors can be connected to these inputs. Softwareselectable gains of 1 and 10 provide effective input
ranges of ±10 V and ±1 V. Each analog input channel
uses a 24-bit Delta-Sigma analog-to-digital converter(ADC) that provides anti-aliasing filtering based on
the clock rate. In addition to acquiring data from theanalog input channels, the DT7837 supports the ability
to simultaneously acquire the value of the tachometer
input, general-purpose counter/timer, measure counter,and digital input port in the analog input stream,
allowing precise correlation of all input signals.

The Digital connector on the board provides access to thedigital I/O lines through general-purpose I/O pins. Users
can redefine these pins for use as the counter/timer gate,counter/timer input, counter/timer output, or external
trigger signal, as required by their application.

General Purpose Counter/Timer

IEPE Support

The general-purpose counter/timer on the DT7837
module supports the following counter/timer operation
modes:

Applications that require accelerometer, vibration, noise,or sonar measurements often use IEPE sensors. IEPE
conditioning is built-in to the analog input circuitry of theDT7837 module. Each analog input channel provides thefollowing capabilities for IEPE support:• Event Counting – Counts the number of rising edges
that occur on the counter’s input signal whenever
the gate is active• Rate Generation – Generates a continuous pulse
output signal whenever the gate is active• Non-repeatable one-shot – Generates a single
output pulse whenever the gate is active (afterthe pulse period from the previous output pulseexpires). Any gate signals that occur while the pulse
is being output are not detected.
• Idle – The counter no longer drives the clock outputsignal.
Users can program the gate type, C/T clock source, pulse
width, pulse output period, and pulse output polarity.

• Excitation current source – Internal excitation
current source of 4 mA.

• Coupling Type – Software-programmable AC
coupling or DC coupling.

• Compliance Voltage – +20 V(508) 946-5100

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Measure Counter

Output Triggers

DT7837 module provides one measure counter. Using thiscounter, you can measure the frequency, period, or pulse
width of a single signal or the time period between twosignals and return the value in the analog input stream.
This is useful for correlating the analog input data withdigital positional data, measuring the frequency of asignal, or as a tachometer. An internal 48 MHz counter isused for the measurement, yielding a resolution of 20.83
ns (1/48 MHz).

To start an output operation, the following output triggers
are supported:• software trigger• external digital (TTL) positive or negative
Simultaneous Input and Output Operations
The DT7837 supports the ability to continuously acquire
data from the input stream and continuously output datafrom the channels in the output stream simultaneously.

Analog Output Channel

Triggering Acquisition on Multiple Modules

The DT7837 provides one high speed, 24-bit analog
output with an output range of ±10 V. The module
provides a two-pole Butterworth filter and quiet start
circuitry to prevent noise from interfering with theoutput signal.

The internal clock on the DT7837 module is derived fromthe 48 MHz crystal oscillator and provides the timing
for the analog input subsystem on the module. You canstart acquisition on multiple modules by connecting
all modules to a shared external trigger input. Usingsoftware, you must define one of the general-purpose
input pins on the Digital connector on each DT7837
module as the external trigger signal. When triggered,the modules start acquiring data at the same time.

The DT7837 supports single-value and continuous analog
output operations. In addition, the digital output port
can be updated simultaneously with

Analog Output Clock
SoftwareThe DT7837 supports an internal D/A clock, which isderived from the 48 MHz crystal oscillator. The clock
frequency of the D/A output clock can be programmed
to a value between 30 kHz and 216 kHz for pacing
output operations.

The DT7837 modules run Linux 3.12 (Debian distribution)with custom loadable kernel modules (LKM) or device
drivers.
The DT7837 device drivers and numerous example
application programs reside on the DT7837 module. The
drivers are loaded when the DT7837 module is poweredup. The device drivers (DT7837 driver and DT7837 USBdriver), shown in the block diagram below, expose
the functionality of the module to Linux user space
applications using virtual file interfaces.

The DT7837 runs Linux 3.12 with custom loadable kernel modules, i.e., “device drivers” for the board hardware. These“drivers” expose the functionality of the board to Linux user space applications.
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The DT7837 module uses the following virtual files toaccess its subsystems:
•••
•
•••
•
•

For instance, to access the digital input subsystem on
the DT7837 module, the application uses the virtual filehandle for the digital input subsystem (/dev/dt7837-din)
as follows.

/dev/dt7837-ain – Analog input subsystem.
/dev/dt7837-aout – Analog output subsystem.
/dev/dt7837-din – Digital input subsystem.
/dev/dt7837-dout – Digital output subsystem.
/dev/dt7837-tach – Tachometer input subsystem.
/dev/dt7837-measure – Measure counter subsystem.
/dev/dt7837-ctr-tmr – Counter/timer subsystem.
/dev/dt7837-stream-in – Input stream.
/dev/dt7837-stream-out– Output stream.

1.

Open the file /dev/dt7837-din, thereby allowing
access to the digital input subsystem.
2. If supported, configure parameters for the digital
input subsystem using IOCTL commands.
3. Read from the file, which in turn, reads the value ofthe digital input port and returns a value.
4. Close the file.

DT7837 Example Programs

The USB device functionality of the DT7837 is accessible
to user-space embedded applications using the following
files:
••
•
•
•
•
•

The DT7837 ships with many example programs that
demonstrate the capabilities of the hardware. They alsoillustrate how user programs communicate with theDT7837 drivers using file I/O commands and IOCTLs. All
examples are written in ANSI C, are open source, andinclude make files that allow them to be built using the TI
SDK tool chain and cross compilers.

/dev/dt7837-ep1in - EP1 IN endpoint.
/dev/dt7837-ep1out - EP1 OUT endpoint.
/dev/dt7837-ep2in - EP2 IN endpoint.
/dev/dt7837-ep2out - EP2 OUT endpoint.
/dev/dt7837-ep3out - EP3 OUT endpoint.
/dev/dt7837-ep4out - EP4 OUT endpoint.
/dev/dt7837-ep5out - EP5 OUT endpoint.

Users can build these example programs, use them to test
their hardware, and modify them as needed to get up
and running quickly.

User applications can perform standard file operations
such as open, close, read, and write on the virtual files
to access and control the hardware or to send data to theUSB host through an IN endpoint and receive data fromthe USB host through an OUT endpoint.

DT7837 example programs allow users to get up and running applications.

The following example programs are provided:

••

•

•
•

aio-in – Performs an asynchronous analog input
operation, generating a sine wave, triangle waveform,or sawtooth waveformfunction-gen – Performs an asynchronous analog
output operation, generating a sine wave, triangle, orsawtooth waveform using Direct Digital Synthesis.
aout-single – Performs a synchronous write operationon the analog output channel.

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clk-gen – Uses the counter/timer to generate anoutput clock.
common – Includes common functions used by theother example programs.
data-logger – Acquires data from all the channels
in the input stream and stores it to a file. Many fileformats are supported.
usb-loopback – Demonstrates use of the gadget USB
driver to send data from a host application to theDT7837 using and OUT USB pipe and to receive datafrom the DT7837 using IN USB pipe.
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• digio – Performs a synchronous write operation on the digital output
port, and then reads back the value that was output by performing a
synchronous read operation on the digital input port.
• dt7837-calibration – A command-line program that calibrates theanalog input and analog output circuitry of the DT7837 module.
• event-counter - Performs an event counting operation.
• sig-analyzer – An embedded web server and signal analyzer. It
acquires data from two analog input channels and performs and FFTon the data. The results are displayed to a client’s web browser whenconnected to the device.
• fir-filter - Performs an input stream and an output stream operation
simultaneously and continuously. Data from the input stream is filteredand then output from the analog output channel.
• web-calibration – A web-based calibration program that calibrates theanalog input and analog output circuitry of the DT7837 module.
• web-server – An embedded web server that performs most of thefunctions of the DT7837 module and saves the acquired data to a file.

Ordering Summary
HARDWARE• DT7837 — 4-channel ARM Module
ACCESSORIES:• DT7837 Accessory Kit — Includes STP26 Screw
Terminal Panel, EP405 USB To Serial TTL Debug
Cable, EP361 Power Supply, USB Cable, andEthernet Cable
OR ORDER SEPARATELY• STP26 — Screw Terminal Panel with EP406 Cable• EP405 — USB to Serial TTL Debug Cable• EP361 — +5 V DC Power Supply and Cable

The DT7837 showing outstanding dynamic performance on a -6 dB sine wave at 1 kHz, including ENOB
(Effective Number of Bits) of 15.9.

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DT7837-Datasheet		

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June 2017. Rev 6© Measurement Computing Corporation