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Semtech SX8724SEVK User Manual

Evaluation kit for sx8724s data acquisition system
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ADVANCED COMMUNICATIONS & SENSING
SX8724SEVK USER GUIDE
Evaluation Kit for SX8724S Data Acquisition System
Description
The SX8724SEVK is a platform for SX8724S evaluation
and sensing application prototyping. It consists of a
single board with the ZoomingADC device interfaced to
the computer through a USB gateway.
All SX8724S I/Os are available and placed on breakout
pads for easy access. The tool is intended to be the
interface between the sensor and the PC in order to
ease the handling of the SX8724S.
Equipment Needed
PC with Windows XP or a latest version
Powered USB 2.0 port
Ordering Informations
EVK Part Number
Function
SX8724SEVK
SX8724S (SPI) Evaluation
ACS - Revision 1.0
© Semtech Corp.
May 2011
Evaluation Kit for SX8724S Data Acquisition System
Features
Evaluation Board
• Directly connects most types of sensors
• Extended temperature range from -40 to 125°C
• 2.4V to 5.5V operation
• Supply from 5V USB, externally or regulated 3.3V
• USB interface with gateway to the SX8724S
• On board master MCU with flash memory, access
to all IO
• Prototyping area
• I/Os, board supplies and grounds placed on pads
Graphical User Interface
• Easy settings through registers and controls
• System and device performance analysis tool
• Save and load configurations
• Log to file
SX8724S ZoomingADC System Evaluation
• Up to 16-bit differential data acquisition
• Programmable gain: (1/12 to 1000)
• Sensor offset compensation up to 15 times full
scale of input signal
• 3 differential or 6 single-ended signal inputs
• Programmable Resolution versus Speed versus
Supply current
• External reference input voltage
• Internal reference output
• Digital outputs to bias sensors
• Low-power (250 uA for 16b @ 500 S/s)
Digital Interface
• Access to SPI signal
• ADC conversion ready
• 2 GPIO
• Possibility to chain boards on the same bus
Application Examples in this User Guide
• Interfacing your first pressure sensor
Page 1
SX8724SEVK
USER GUIDE
www.semtech.com

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  • Page 1 SX8724SEVK USER GUIDE Evaluation Kit for SX8724S Data Acquisition System Description Features The SX8724SEVK is a platform for SX8724S evaluation Evaluation Board and sensing application prototyping. It consists of a • Directly connects most types of sensors single board with the ZoomingADC device interfaced to •...

  • Page 2: Table Of Contents

    Reading the sensor using the GUI ............40 ACS - Revision 1.0 May 2011 Page 2 www.semtech.com © Semtech Corp.
  • Page 3 ZoomingADC™ Benefits ............. . 49 ACS - Revision 1.0 May 2011 Page 3 www.semtech.com © Semtech Corp.

  • Page 4: Getting Started

    The SX8724S is a signal conditioner based on Semtech's ultra low power ZoomingADC™ technology. It directly connects most types of miniature sensors with a general purpose microcontroller. The SX8724SEVK is a USB based evaluation tool designed to allow simple and easy evaluation of the suitability of the SX8724S device for a given application.

  • Page 5: Board Overview

    SX8724SEVK Evaluation Kit for SX8724S Data Acquisition System ADVANCED COMMUNICATIONS & SENSING USER GUIDE Board Overview The picture below describes the main zones and functions accessible on the SX8724SEVK. USB Gateway Interface & Power Management Isolate/connect device Acquisition Device Analog Interface &...

  • Page 6: Software Installation

    If the evaluation kit is supplied with an insert sheet, follow the instruction on the insert sheet. The latest software revision can be downloaded on Semtech website. 1. Put the CDROM in your computer and browse the contents of the CD, open the SX8724xEvaluationKitSetup.exe file manually.

  • Page 7: About Microsoft .Net Framework

    There are multiple versions of the .NET Framework available from Microsoft, and they can be installed side-by- side on the same computer. Contact your system administrator for more details. ACS - Revision 1.0 May 2011 Page 7 www.semtech.com © Semtech Corp.

  • Page 8: Board Connection And Drivers Installation (First Time)

    Validate always by clicking the “Continue Anyway button”: 4. The drivers are now installed. The board and its dedicated software are ready to be used. Launch SX8724xEVK software from the Windows Start menu. ACS - Revision 1.0 May 2011 Page 8 www.semtech.com © Semtech Corp.

  • Page 9: Hardware Description

    W1 3 W1 4 READY 22nF READY SCLK W1 5 VPUMP VPUMP AGND W1 6 MISO/READY MISO/READY W1 7 READY W1 8 S X8 724S W1 9 W2 0 ACS - Revision 1.0 May 2011 Page 9 www.semtech.com © Semtech Corp.

  • Page 10: User Interfaces

    Connect SX8724S READY VBATT pin to supply signal to gateway (or measure current) Digital interface Analog interface + Vref,in and Vref,out Figure 5. SX8724S Interface on the Board ACS - Revision 1.0 May 2011 Page 10 www.semtech.com © Semtech Corp.

  • Page 11: Prototyping Area

    ADVANCED COMMUNICATIONS & SENSING USER GUIDE Prototyping Area Using the prototyping area, one can set its own application only using the SX8724S and bypassing the onboard gateway. Figure 6. Prototyping Area ACS - Revision 1.0 May 2011 Page 11 www.semtech.com © Semtech Corp.

  • Page 12: Power Supply

    Table 1. Power Sources Specifications Voltage range Unit Comment VBUS DC, Unregulated DC, Regulated VLDO VEXT DC, Unregulated Board current driving capability Temperature range from -40 to 85°C External power supply ACS - Revision 1.0 May 2011 Page 12 www.semtech.com © Semtech Corp.

  • Page 13: Power Supply Selection

    The picture below shows the selector. User should place the jumper on the desired SX8724S supply voltage value. Enter here with an Power LED external power supply Power jumper External voltage 5V from USB Regulated 3.3V Board voltage Figure 8. SX8724SEVK Power Supply Selector ACS - Revision 1.0 May 2011 Page 13 www.semtech.com © Semtech Corp.

  • Page 14: Usb Interface

    Figure 9. PIC Gateway Schematic USB interface PICKit programmer/debugger interface Bootloader mode control PIC gateway Pin access to the PIC gateway Figure 10. PIC Gateway on the Board ACS - Revision 1.0 May 2011 Page 14 www.semtech.com © Semtech Corp.
  • Page 15 Bootloader Mode The BOOT LOADER (J9) jumper allows the user to set the onboard PIC18F14K50 in bootloader mode and to program it. One can then update the gateway with the latest driver from Semtech website or set its own solution using the SPI interface (see 7.1.

  • Page 16: Evk Bill Of Materials List

    SX8724SEVK Evaluation Kit for SX8724S Data Acquisition System ADVANCED COMMUNICATIONS & SENSING USER GUIDE EVK Bill of Materials List Table 2. SX8724SEVK Bill of Material Package Description Manufacturer Part# MLPQ-16 4x4 SX8724S acquisition system SEMTECH SX8724SWLTDT SSOP-20, 6.5mm pitch PIC Gateway...
  • Page 17 SX8724SEVK Evaluation Kit for SX8724S Data Acquisition System ADVANCED COMMUNICATIONS & SENSING USER GUIDE Table 2. SX8724SEVK Bill of Material Package Description Manufacturer Part# SMD 0603 100nF SMD 0603 C12, 22pF SMD 0603 47nF SMD 0603 22nF SMD 0603 ACS - Revision 1.0...

  • Page 18: Board Physical Dimensions

    SX8724SEVK Evaluation Kit for SX8724S Data Acquisition System ADVANCED COMMUNICATIONS & SENSING USER GUIDE Board Physical Dimensions Figure 12. SX8724SEVK Board Overview ACS - Revision 1.0 May 2011 Page 18 www.semtech.com © Semtech Corp.

  • Page 19: Graphical User Interface

    GRAPHICAL USER INTERFACE Software Tool Overview The SX8724SEVK includes a graphical user interface (GUI) that provides simplified access to all key registers on the board. It uses intuitive controls and popup menus to write settings from the hardware. This GUI takes high level input from the user and computes the required low level register values. With the GUI, the user is not required to compute complicated equations to determine which values must be written for board operation.

  • Page 20: Main Window

    Show registers toggles the SX8724S Registers display window and may also be accessed through the short cut buttons of the Window Toolbar. The register display window indicates the status of SX8724S ACS - Revision 1.0 May 2011 Page 20 www.semtech.com © Semtech Corp.
  • Page 21 Help opens a HTML help window with GUI controls descriptions. User's Guide… opens a PDF version of the User Guide. About… provides details of the GUI revision. The latest version of the GUI can be downloaded from Semtech web site. Figure 16. Help Menu Options ACS - Revision 1.0...

  • Page 22: Window Tool Bar

    Reset, Refresh and Show registers provides a direct control of the actions described in 13.1.2. Action Menu button Help button provides a direct control of the actions described in 13.1.3. Help Menu. Figure 18. Example Configuration File Text Editor Output ACS - Revision 1.0 May 2011 Page 22 www.semtech.com © Semtech Corp.

  • Page 23: Status Bar

    The Status Bar provides error messages, the onboard SX8724S version and the current user configuration file. For further information concerning the IC revision, please refer to the SX8724S datasheet. Message IC Revision Number Configuration File Figure 19. Status Bar ACS - Revision 1.0 May 2011 Page 23 www.semtech.com © Semtech Corp.

  • Page 24: Zoomingadc Controls

    The group of controls named “PGA” lets the user control the gain, offset and enabling disabling each PGA individually. The user has also the possibility to control the PGAs biasing current ratio. ACS - Revision 1.0 May 2011 Page 24 www.semtech.com © Semtech Corp.
  • Page 25 GPIO controls. If direction is set as “OUT”, the corresponding pin can be set as output high or low. The digital pins are able to deliver a driving current up to 8 mA. D0 and D1 are multi-functional pins, see 13.4.8. Mode. for GPIO with V functionality. ACS - Revision 1.0 May 2011 Page 25 www.semtech.com © Semtech Corp.
  • Page 26 VREF on D1 pin allows to select D1 pin as reference voltage for the acquisition chain. As described in Section 13.4.1, D1 can input a V . When using an external V input, it may have any value REF,ADC between 0V and V BATT ACS - Revision 1.0 May 2011 Page 26 www.semtech.com © Semtech Corp.

  • Page 27: Voltage Control

    Input referred noise – the simple noise model described in the datasheet is used to estimate the equivalent input referred rms noise V of the acquisition chain. It is computed with the extracted rms output noise N,IN ACS - Revision 1.0 May 2011 Page 27 www.semtech.com © Semtech Corp.
  • Page 28 V [ ] ----------- - – the time of the conversion sequence for one sample is computed as: CONV ⋅ ELCONV s [ ] ------------------------------------------------------------- - CONV ACS - Revision 1.0 May 2011 Page 28 www.semtech.com © Semtech Corp.

  • Page 29: Display Chart

    The display chart is a graphic representing the ADC output samples. An enlarged graph including a histogram and measured system performance is available when pressing the button and is described in ZoomingADC Data Display Window section. Figure 24. Display Chart ACS - Revision 1.0 May 2011 Page 29 www.semtech.com © Semtech Corp.

  • Page 30: Log Data To File

    Browse... button let the user choose where to store the log file and which name it will have. Start/Stop start the logging process or stop it. While the logging process is running a progress bar will show the progress. ACS - Revision 1.0 May 2011 Page 30 www.semtech.com © Semtech Corp.

  • Page 31: Zoomingadc Data Display Window

    Holding it pushed also enables the pan command. To reset the display to default range, the right button of the mouse provides the Undo All Zoom/Pan operation (see Section 14.1.3.) ACS - Revision 1.0 May 2011 Page 31 www.semtech.com © Semtech Corp.

  • Page 32: Histogram Panel - Noise Analysis

    This parameter is computed from the N,IN output rms noise (code) and the total PGA gain: N OUT ----------------- - Vrms N IN GDtot ACS - Revision 1.0 May 2011 Page 32 www.semtech.com © Semtech Corp.
  • Page 33 1.Digital averaging increases resolution and reduces noise. The effects of input-referred noise is reduced by digital averaging on the buffer of samples used to compute the Measured System Performances. Therefore, the ENOB DC value can be higher than the sample width limitation (>16 bits). ACS - Revision 1.0 May 2011 Page 33 www.semtech.com © Semtech Corp.

  • Page 34: Registers Display Window

    By depressing the <CTRL>+<ALT>+<N> keys of the PC keyboard simultaneously, the user can write to the configuration registers to verify propose settings, as well as load and save configuration files (*.cfg). ACS - Revision 1.0 May 2011 Page 34 www.semtech.com © Semtech Corp.

  • Page 35: Application Examples

    Interfacing your first pressure sensor 17.1 Introduction This chapter intends to show how to interface a pressure sensor using the SX8724SEVK evaluation board. It also shows how to use efficiently the ZoomingADC™ of the SX8724S and demonstrate the benefits of the zooming feature.
  • Page 36 Figure 29. Sensor transfer function Note: The given transfer function in the datasheet is for a 10V power supply, here the transfer function was translated for a 3.3V power supply. ACS - Revision 1.0 May 2011 Page 36 www.semtech.com © Semtech Corp.
  • Page 37 VOUT- ± ± ± Voff Voff Vref PGA1 PGA2 PGA3 Analog Inputs Reference Inputs REF,ADC VBATT VREF VMUX ANALOG ZOOM Figure 30. Sensor schematic connection to the SX8724S ACS - Revision 1.0 May 2011 Page 37 www.semtech.com © Semtech Corp.
  • Page 38 The picture below shows how to connect the sensor on the evaluation board, each red point represents a connection. 4: Vout- 3: Vb 2: Vout+ 1: GND PIN 1 Figure 31. Connection on the SX8724SEVK Evaluation board ACS - Revision 1.0 May 2011 Page 38 www.semtech.com © Semtech Corp.

  • Page 39: Using The Evaluation Board And The Gui

    After a Power-on-reset the GPIO are set to a digital output low state. The sensor bias is connected to D0 pin. Switch ON the “D0” “Out” control to set this GPIO as output high state to drive the sensor. Figure 33. “GPIO” settings ACS - Revision 1.0 May 2011 Page 39 www.semtech.com © Semtech Corp.

  • Page 40: Reading The Sensor Using The Gui

    ). Change this and select V as voltage reference for BATT the acquisition chain. The “Reference” configuration control should look like the picture below Figure 35. Reference Voltage Selection ACS - Revision 1.0 May 2011 Page 40 www.semtech.com © Semtech Corp.
  • Page 41 The gain that needs to be applied to see the full range of the signal is then calculated as follows: ADCOut 3300 Gain SensorOut Equation 1 This means PGA1 gain GD1=10, PGA2 gain GD2=10 and PGA3 gain GD3=2.25 (granularity of PGA3 = 1/12). ACS - Revision 1.0 May 2011 Page 41 www.semtech.com © Semtech Corp.

  • Page 42: Zoomingadc™ Configuration

    1. The maximum output span of the ADC, here 3.3V 2. The maximum output span value of the sensor in the measuring window, here around 8.5-4.5 = 4mV ACS - Revision 1.0 May 2011 Page 42 www.semtech.com © Semtech Corp.
  • Page 43 As computed, the PGA gains can be raised to 825. The offset is 19/12 (see “Offset Cancellation” on page 43), as the input signal and the reference are non- inverted, the offset has to be positive. ACS - Revision 1.0 May 2011 Page 43 www.semtech.com © Semtech Corp.
  • Page 44 Evaluation Kit for SX8724S Data Acquisition System ADVANCED COMMUNICATIONS & SENSING USER GUIDE The “PGA” group of controls should then look like as picture beside. Figure 39. SX8724S “PGA” final configuration ACS - Revision 1.0 May 2011 Page 44 www.semtech.com © Semtech Corp.

  • Page 45: Adc Configuration

    ± AC 2 VOUT - ± ± ± Voff Voff Vref PGA1 PGA2 PGA3 Analog Inputs Reference Inputs REF,ADC VBATT VREF VMUX ANALOG ZOOM Figure 40. PGA Parameters ACS - Revision 1.0 May 2011 Page 45 www.semtech.com © Semtech Corp.
  • Page 46 Elementary conversions Resolution Conversion time 4.108 LSB equivalent input voltage 62.47 649E-09 Vrms Equivalent input noise PGA settling time 2.048 ADC quantization noise only PGA white noise included ACS - Revision 1.0 May 2011 Page 46 www.semtech.com © Semtech Corp.

  • Page 47: Noise Cancellation

    The OSR and N parameters can be increased in order to reduce the noise generated by the ADC and ELCONV PGAs. Noise with OSR=512, N ELCONV Noise with OSR=1024, N ELCONV ACS - Revision 1.0 May 2011 Page 47 www.semtech.com © Semtech Corp.

  • Page 48: Lsb Equivalence

    The approximate equivalence between Pressure and altitude is defined as follow: ⋅ 0.96Pa 8620m ≡ → -------------------------------------- - Altitude 100kPa 8620m 0.0079Pa 100kPa Equation 5 This implementation has a resolution of 8cm altitude. ACS - Revision 1.0 May 2011 Page 48 www.semtech.com © Semtech Corp.

  • Page 49: 17.10 Zoomingadc™ Benefits

    Figure 42. Signal Span Using Zooming Settings The signal span is 11743–1374=10370 bits which corresponds to a 320% gain on the signal reading allowing you to have more consistent readings. ACS - Revision 1.0 May 2011 Page 49 www.semtech.com © Semtech Corp.
  • Page 50 FAR EAST Tel: +886 2 2748 3380 Fax: +886 2 2748 3390 Semtech Ltd., Units 2 & 3, Park Court, Premier Way, Abbey Park Industrial Estate, Romsey, Hampshire, SO51 9DN. EUROPE Tel: +44 (0)1794 527 600 Fax: +44 (0)1794 527 601...
  • Page 51 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Semtech SX8724SEVK...

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