ANALOG DEVICES EVAL-ADXL35x-SDP Evaluation Board User Guide

**ANALOG DEVICES EVAL-ADXL35x-SDP Evaluation Board User Guide

**

FEATURES

• Separates device under test (DUT) from controller for accurate environmental testing
• Data capture up to maximum device output data rate (ODR)
• Standard USB cable for power and communications
• PC-based, user friendly graphical user interface (GUI)
• Fast and easy installation
• Captures, visualizes, and saves the data

GENERAL DESCRIPTION

This user guide provides comprehensive instructions for configuring both the hardware and software required to utilize the EVALADXL35x-SDP as a user friendly, PC-based solution for evaluating the ADXL355/ADXL357 (digital output only) microelectromechanical

systems (MEMS) accelerometers. The EVAL-ADXL35x-SDP offers direct PC connectivity. Also, it allows linking the DUT and processor board to diverse platforms. The user friendly GUI simplifies data collection, operational configuration, and motion profile observation. This user guide gives an overview of using the EVAL-ADXL35xSDP, detailing its functionality with provided examples where relevant.

Figure 1 shows the required hardware components. The EVALSDP-CB1Z is a system demonstration platform (SDP) controller board that provides a means of communication with the sensor from the PC. The EVAL-SDP-INTER4-Z is an SDP interface board that serves as an interposer between the SDP controller board and the evaluation board. The EVAL-ADXL35xZ is the DUT breakout board.

SETTING UP THE EVALUATION SYSTEM

The following steps describe the installation process for the ADXL357 evaluation system, as an example. Same steps apply to the ADXL355.

HARDWARE CONFIGURATION

To configure the hardware, follow these steps:

1. Connect the SDP interface board (EVAL-SDP-INTER4-Z) to the SDP controller board (EVAL-SDP-CB1Z) using the 120-pin small foot print connectors as shown in Figure 2.
   

2. Connect the SDP interface board to the EVAL-ADXL35xZ using the provided cable.

   • One end of the cable features a Harwin connector designed to link with the SDP interface board, as illustrated in Figure 3.

   • The other end of the cable has two 3 × 2 pin header connectors, which are used for connecting to the EVAL-ADXL35xZ as shown in Figure 3.

   • For a visual guide on correctly aligning the cable on both the SDP interface side and the EVAL-ADXL35xZ side, check the red arrows in Figure 3 and Figure 4, respectively
     

3. Connect one end of the mini-B USB cable to the SDP-B controller board, and plug the other end of the cable into the PC. Figure 1 shows an overview of the complete setup and connections.

SOFTWARE INSTALLATION

1. Download the software installer on the PC by clicking the EVAL-ADXL355-SDP Software for the EVAL-ADXL355-SDP or the EVAL-ADXL357-SDP Software for the EVAL-ADXL357-SDP on the EVAL-ADXL35x-SDP website.

2. Once downloaded, extract the files to the desired local drive.

3. Double click on EVAL-ADXL357-SDP_install to start the installation process (see Figure 5).
   

4. Simply follow the on-screen instructions, including choosing the preferred installation path and accepting the license agreement, until the evaluation platform and SDP driver installation are complete, as shown in Figure 6.
   

SOFTWARE STARTUP

1. After the installation is complete, the software can be run through the installation directory by launching EVAL-ADXL357- SDP.exe (see Figure 7), or the user can simply type EVALADXL357-SDP in the Windows search bar and press the enter key on the keyboard to start the software.
   

2. When launching the software without connecting the evaluation board setup to the computer, the Hardware Select window appears as it searches for the connected hardware (see Figure 8).

   • To use the board, connect the setup to the computer using a USB cable. Once connected, the software automatically detects the hardware, and user can select it for use (see Figure 9).

   • Note that the name of the hardware recognized in the Hardware Select window matches the name of the interface board.

   • If the evaluation board is already connected to the computer when the user runs the software, the Hardware Select window does not appear. In this case, if everything works as expected, the system reads the entire register map from the accelerometer and displays it on the ADXL35x Register Map section of the GUI, on the gray rectangle to the right instead (see Figure 10).

   • One way to verify that the system is working properly is by checking that the ADXL35x Register Map fields read the expected values. For example, the DEVID_AD register must read AD.

3. If the hardware is not recognized in any of the ways mentioned, the user can resolve this issue by following these steps:
   a. Close the software completely.
   b. Reopen the software.
   c. If the hardware is still not recognized, attempt to disconnect then reconnect the evaluation board to the computer, ensuring a secure connection.
   d. Once the hardware is successfully connected and recognized, the user can access the register map as described in Step 2.

ADXL35X GRAPHICAL USER INTERFACE

GETTING STARTED

The ADXL355/ADXL357 demonstration platform provides a user friendly interface divided into separate tabs (see Figure 11), each tailored for common accelerometer measurements. This approach enables users to quickly capture data for various tests without the need for custom hardware or software development. For a quick overview of the functionality of each tab, refer to the information presented in Table 1.

the activity interrupt response real time
FFT| Continuous FFT plotting, 1024 samples per loop.
Self Test| Demonstrates self test functionality.
Tilt Sensing| 3D tilt sensing. Offset and sensitivity calibration.

SHARED COMMANDS BETWEEN TABS

The GUI provides options to configure the several features of the accelerometer, namely Power Mode, Output Data Rate, High Pass Filter, and Range, which are grouped in the Basic Configuration window. Other GUI functionalities like option to save the data to file and scaling of the accelerometer data to LSB or gee values are also available within this window

• Power Mode. Ensure that the power mode is set to Measure when capturing data (see Figure 12)
  

• Output Data Rate. ODR determines the rate at which data is sampled. The user has the flexibility to select the preferred ODR, ranging from 3.096 Hz to 4000 Hz, simply by accessing the Output Data Rate dropdown menu. Note that the bandwidth for the ADXL355/ADXL357 must be approximately 1/4 of the ODR.

Figure 13 illustrates the impact of varying ODR settings on capturing the acceleration data when the sensor is shacked by hand. It shows that when data sampling rate is low (3.096 Hz), the captured data is not representing the actual hand shaking excitation as the sample rate is slower than the hand shake frequency (as shown in the top image of Figure 13). This slower rate may result in data loss. Conversely, when data is sampled at 500 Hz, it appears significantly faster and smoother and the captured data follows the hand shaking acceleration as demon- started in the bottom image of Figure 13.

• High Pass Filter. The ADXL355/ADXL357 include an optional digital high-pass filter with a programmable corner frequency. The high-pass corner frequency, where the output is attenuated by 3 dB, is related to the ODR, and the HPF_CORNER setting in the filter register (Register 0x28, Bits[6:4]). The high-pass filter is disabled by default. Figure 13 shows the HPF settings, which are proportional to the ODR.
• Range. There are three user selectable ranges available for measuring acceleration. Users can adjust the range from ±2 g to ±8 g for the ADXL355 and from ±10 g to ±40 g for the ADXL357 (see Figure 12).
• Offset Trim (g). The user has the option to set the offset value for each axis in the Offset Trim (g) section. This feature allows the user to eliminate offsets in any of the axes, providing the trimmed data as the resulting output (see Figure 12).
• File Path. All data can be saved with a custom name to a specified path in either gee or LSB format (see Figure 14). There are alternative methods for accessing data. When right click on the measurement window, various export options (such as to clipboard or to Excel) appear. Additionally, a screenshot of the window can be copied using the Copy Data option. Note that the export method is designed to capture the data currently displayed in the window, with a maximum of 10,000 samples
  

(see Figure 15) while saving the data as a file in a specific path allows for saving all the data without the 10,000-sample limit.

• Start Data Capture/Stop Data Capture and Quit. These commands are universally accessible across all tabs. Clicking Start Data Capture initiates data collection on the current tab. Once activated, Start Data Capture is automatically grayed out and disabled until the user presses Stop Data Capture. Quit allows the user to exit the GUI (see Figure 14).

DEVICE OVERVIEW TAB

The Overview tab allows the user to capture acceleration data in three different axes based on the preconfigured settings. The real-time graphs in the main window display the acceleration data for each axis as a function of the number of samples collected (see Figure 16).

ACTIVITY DETECTION TAB

The activity tab allows the user to evaluate the activity feature. The activity is set when the measured acceleration on any axis is above the activity threshold (ACT_THRESH) for specific consecutive measurements (ACT_COUNT). Figure 17 shows an example at which the activity box is checked for the X-axis and it shows the ACT_EN register is updated to only enable activity on the X-axis. It can be enabled for multiple axes as shown in Figure 18. The next settings are Activity Threshold and Activity Counter. The user can define the threshold for activity detection in the Activity Threshold dialog box. To trigger the activity interrupt, the measured acceleration must be above the threshold for at least the specified number of samples on the activity counter, which can be defined in the Activity Counter dialog box. For this example, Activity Threshold is set to 3 g and Activity Counter is set to 2. If there is any activity more than 3 g for at least 2 samples, the activity detects in the X-axis as shown in Figure 17. The bottom plot shows the activity bit going from low to high when the activity is detected

Activity detection can be activated for all three axes as shown in Figure 18.

FFT TAB

The FFT tab provides the frequency analysis of the captured signal using the fast Fourier transform (FFT) method. It utilizes 1024 samples at the selected ODR to create a frequency domain plot. The FFT is configured for four samples RMS averaging and rectangular windowing. Figure 19 shows the FFT plot for a 1 g peak, 200 Hz sinewave excitation.

FFT TAB

The FFT tab provides the frequency analysis of the captured signal using the fast Fourier transform (FFT) method. It utilizes 1024 samples at the selected ODR to create a frequency domain plot. The FFT is configured for four samples RMS averaging and rectangular windowing. Figure 19 shows the FFT plot for a 1 g peak, 200 Hz sinewave excitation.

SELF TEST TAB

The ADXL355/ADXL357 incorporate a self test feature that effectively tests its mechanical and electronic systems simultaneously. When the self test function is enabled, an electrostatic force is exerted on the mechanical sensor. The self test feature rejects externally applied acceleration and only responds to the self test force, which allows an accurate measurement of the self test, even in the presence of external mechanical noise.

The Self Test tab demonstrates how this function operates for each axis. Once the Start Data Capture button is clicked, the software acquires one second of data from the ADXL355/ADXL357 at the user specified data rate. The ST1 bit invokes self test mode. Enabling the ST2 bit applies an electrostatic force to the mechanical sensor and induces a change in output in response to the force. The self test delta is the difference in output voltage in the Z-axis when ST2 is high vs. ST2 is low, while ST1 is asserted. ST1 and ST2 can be accessed through the SELF_TEST register (Register 0x2E).

For example, as shown in Figure 20, for a specific data rate, the self test feature is disabled in default state for the first 109 samples. At the 109th sample, the self test bit is asserted, initiating the self test function. An electrostatic force is applied to the beam, causing the output to shift and remain in this state until the 210th sample. At this point, the self test bit is disserted, and the device output returns to normal.

TILT SENSING TAB

In the Tilt Sensing tab, the user can measure the incline angle of the accelerometer in each direction. As illustrated in Figure 21, θ represents the inclination of the X-axis, ψ corresponds to the inclination of the Y-axis, and Φ denotes the inclination of the Z-axis. The reference point, which is shown as a circle, is highlighted with a dashed red circle in both Figure 21 and Figure 22
.

To ensure precise results, the software provides a calibration option using gravity acceleration. Click the Calibrate button to initiate the process. Subsequently, six pop-up dialog boxes guide the user through specific orientations for the evaluation board to expose each axis to a ±1 g field. Figure 22 illustrates the first dialog box, providing instructions on how to position the part to expose the X-axis to a 1 g field.

Afterward, the software calculates the offset and sensitivity calibration coefficients for each axis in gs (see Figure 23).

ESD Caution
ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality.

Legal Terms and Conditions
By using the evaluation board discussed herein (together with any tools, components documentation or support materials, the “Evaluation Board”), you are agreeing to be bound by the terms conditions set forth below (“Agreement) unless you have purchased the Evaluation Board, in which case the Analog Devices Standard Terms and Conditions of Sale shall govern. Do not use Evaluation Board until you have read and agreed to the Agreement. Your use of the Evaluation Board shall signify your acceptance of the Agreement. This Agreement is made by and between (“Customer”) and Analog Devices, Inc. (“ADI”), with its principal place of business af Subject to the terms and conditions of the Agreement, ADI hereby grants to Customer a free, limited, person temporary, non-exclusive, non-sublicensable, non-transferable license to use the Evaluation Board FOR EVALUATION PURPOSES ONLY. Customer understands and agrees that the Evaluate Board is provided for the sole and exclusive purpose referenced above, and agrees not to use the Evaluation Board for any other purpose. Furthermore, the license granted is expressly m but not limited to soldering or any other activity that affects the material content of the Evaluation Board. Modifications to the Evaluation Board must comply with applicable law, including not limited to the RoHS Directive. TERMINATION, ADI may terminate this Agreement at any time upon giving written notice to Customer. Customer agrees to return to ADI the Evaluation Bo at that time LIMITATION OF LIABILITY THE EVALUATION BOARD PROVIDED HEREUNDER IS PROVIDED “AS IS” AND ADI MAKES NO WARRANTIES OR REPRESENTATIONS OF A KIND WITH RESPECT TO IT. ADI SPECIFICALLY DISCLAIMS ANY REPRESENTATIONS. ENDORSEMENTS, GUARANTEES, OR WARRANTIES, EXPRESS OR IMPLIED, RELATED TO T EVALUATION BOARD INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY, TITLE, FITNESS FOR A PARTICULAR PURPOSE OR NONINFRINGEMENT INTELLECTUAL PROPERTY RIGHTS IN NO EVENT WILL ADI AND ITS LICENSORS BE LIABLE FOR ANY INCIDENTAL SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES RESULTI FROM CUSTOMER’S POSSESSION OR USE OF THE EVALUATION BOARD, INCLUDING BUT NOT LIMITED TO LOST PROFITS, DELAY COSTS, LABOR COSTS OR LOSS OF GOODW ADI’S TOTAL LIABILITY FROM ANY AND ALL CAUSES SHALL BE LIMITED TO THE AMOUNT OF ONE HUNDRED US DOLLARS ($100.00) EXPORT Customer agrees that it will not direct Indirectly export the Evaluation Board to another country, and that it will comply with all applicable United States federal laws and regulations relating to exports GOVERNING LAW. This Agree shall be governed by and construed in accordance with the substantive laws of the Commonwealth of Massachusetts (excluding conflict of law rules), Any legal action regarding this Agreement
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