Safari Board

Table of Contents

1. Overview
2. Main Components
3. Configurability
4. Technical Specifications
5. Schematics
6. Bill of Materials

Overview

Arrow Electronics' 'Safari' is a multiple-input multi-channel Sensor Interface Board compatible with the 96Boards Mezzanine Card standards. It features Analog Devices' AD7124-8 19.2kSPS 24-bit Delta-Sigma ADC and allows the User to connect up to 8 differential or 16 single-ended output analog sensors, amplify, bias, digitize and filter the signals and forward to a 96Boards-compatible MCU board, where signals can be processed and sent via WiFi to the cloud.

Safari has been designed to accommodate analog sensors such as but not limited to: temperature, acceleration, pressure, humidity and more- basically anything that puts out an analog voltage can be processed. Input range is from 0V up to 3.3V.

See product brief for a summary of product features and benefits.

Main Components

The Safari board has the following major components- refer to diagrams:

1. Analog Devices AD7124-8BBCPZ 24-bit 16-Channel 19.2kSPS Delta-Sigma ADC
2. Analog Devices ADM1185ARMZ-1 Quad-Input Voltage Monitor and Power Sequencer
3. Screw-terminal inputs for all 16 channels and external voltage references
4. LEDs to indicate power for both Safari and Meerkat boards
5. 40-Pin low-speed connector compatible with 96Boards specifications
6. Jumpers for inputs AIN15 and AIN16 to select between on-board voltage reference and external inputs
7. Jumpers to configure resistive dividers on inputs AIN6 and AIN7
8. Analog Devices ADP7118ARDZ-3.3-R7 3.3V Low Dropout Voltage Regulator
9. Analog Devices ADR4525BRZ-R7 Precision 2.5V Voltage Reference

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Configurability

Safari offers a lot of flexibility for the User from both a hardware and software perspective:

Hardware Configurability

The board has 4 multiple-input connectors running along 3 sides. Each connector uses convenient screw-terminals for attaching sensor leads. Additionally, each connector has its own AVdd and GND connections to allow for a simpler and more streamlined layout when connecting multiple sensors.

There are inputs for connecting two different external voltage references (REF1 and REF2) which can be utilized by the AD7124-8's ADC when performing conversions. Inputs for external source REF1 are available on connector J2. For REF2, jumpers JP5 and JP6 enable the User to select between the on-board precision voltage reference or an external reference whose inputs are available on connector J4. Note these inputs can alternatively be used to connect one or two more sensors, as REF2+ and AIN14 share an input on the ADC, as do REF2- and AIN15.

Jumpers JP1-4 are connected to resistive dividers which allows use of Sensors with a maximum output of either 2.5V or 3.3V on inputs AIN6 and AIN7 while using the on-board 2.5V precision voltage reference. If the User wishes to use an external supply voltage source for 5V, AVdd or IOVdd, the board has been designed to accommodate this; zero ohm resistors R61, R62 or R63 can be unsoldered and the external supply connected to TP53, TP59 and/or AVdd.

For maximum configurability all surface-mount passive components (resistors, capacitors, inductors) are sized 0805 which is large enough for removal and replacement using hand soldering techniques. If the User wishes to modify the low-pass filter on an input for example they can do so this way.

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Software Configurability

The main component on Safari is the AD7124-8 Analog-to-Digital converter- see diagram below. This is more than just a simple ADC; it offers a high level of integration, replacing many discrete components with a single I.C. As shown in the block diagram configurable settings include:

For each channel-

1. Enable or disable, Positive and Negative input source selection
2. Gain- selectable from 1 to 128
3. Input Buffers to allow for use of high-impedance sensors
4. Digital filters- type of filter, sampling rate, notch filters
5. Voltage reference used by the ADC- internal, external- REF1, REF2, AVdd- as well as whether buffers are enabled on the + or - signals from the reference
6. Internal current sources and bias voltages which can be sent out from the I.C., turning inputs into output sources

Global for all channels-

7. Power level (low, medium, high); channel sequencing; diagnostics; clock source; etc.

AD7124-8 Block Diagram

For a full list of configuration settings refer to the 'Registers' section in the AD7124-8 datasheet which can be found by clicking here.

Next- Technical Specifications

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