151 lines
6.0 KiB
HTML
151 lines
6.0 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html xmlns:v="urn:schemas-microsoft-com:vml"
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content="text/html; charset=windows-1252">
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<base target="_parent">
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<link rel="Edit-Time-Data" href="index_files/editdata.mso">
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<title>DAC</title>
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<link rel="themeData" href="index_files/themedata.thmx">
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<link rel="colorSchemeMapping"
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href="index_files/colorschememapping.xml">
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<style>
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</style>
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</head>
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<body style="background-color: white;" alink="#0000ff" lang="EN-US"
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link="blue" vlink="#c40026">
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<div class="WordSection1">
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<p style="text-align: center;" align="center"><span
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style="font-size: 18pt;">DAC</span><br>
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<table class="MsoNormalTable"
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style="border: 3pt outset ; background: rgb(255, 204, 153) none repeat scroll 0% 50%; -moz-background-clip: initial; -moz-background-origin: initial; -moz-background-inline-policy: initial; width: 100%;"
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border="1" cellpadding="0" width="100%">
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<tr>
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<td>
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<p><b><span style="font-size: 18pt;">Readme</b></span>
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<br> <br>
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This is a C language project that configures
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the DAC in a simple software output.
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The analog reference of 2.5V is used for the DAC.
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In the first main, the DAC output occurs in the main program,
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with digital input varying from 0 to 4095.
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In the second main, the DAC output is updated within the TimerG0 ISR,
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creating a sinusoidal wave.
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<br> <br>
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The following scope trace shows the DAC output on PA15. The frequency of
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the sine wave output is <br><br>
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<i>frequency</i> = <i>Interrupt Frequency</i> / <i>Table size</i>
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= 200kHz/64 = 3.125kHz</p>
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<p class="PictureWide"><span lang="en-US"><img src="DACout_voltage.png"
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></span></p>
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<p>
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The spectrum analyzer shows a 1.058dB peak at 3.123 kHz (signal)
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and a -37.16dB peak at 7.024kHz (noise).
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We can calculate SNR as 1.058 minus -37.16dB = 38.2dB.
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One might expect the SNR of a 12-bit DAC to be 20*log(2^12) = 72dB.
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However, without an analog filter, the SNR is limited by the size
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of the table, 20*log(64) = 36.1 dB. You can see individual steps in the above
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analog trace.
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</p>
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<p class="PictureWide"><span lang="en-US"><img src="DACout_spectrum.png"
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></span></p>
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<br> <br>
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Derived from Texas Instrument code
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<ul>
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<li>dac12_fixed_voltage_vref_internal_LP_MSPM0G3507_nortos_ticlang</li>
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<li>dac12_fifo_timer_event_LP_MSPM0G3507_nortos_ticlang</li>
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<li>timx_timer_mode_periodic_sleep_LP_MSPM0G3507_nortos_ticlang</li>
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<li>gpio_toggle_output_LP_MSPM0G3507_nortos_ticlang</li></ul>
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</td>
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</tr>
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</table>
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</p>
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<table class="MsoNormalTable"
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style="border: 3pt outset ; background: rgb(252, 243, 144) none repeat scroll 0% 50%; -moz-background-clip: initial; -moz-background-origin: initial; -moz-background-inline-policy: initial; width: 100%;"
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border="1" cellpadding="0" width="100%">
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<tbody>
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<tr>
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<td>
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<p><b><span style="font-size: 18pt;">Hardware Required</b></span>
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<br>
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<ul>
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<li>MSPM0G3507 LaunchPad™ Development Kit (LP-MSPM0G3507)</li>
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</ul>
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<b><span style="font-size: 18pt;">Pin assignments</b></span>
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<br>
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<ul>
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<li>Output: PA0 is red LED1, index 0 in IOMUX PINCM table</li>
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<li>Analog output: PA15 J3.30 DACout</li>
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</ul>
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<b><span style="font-size: 18pt;">LaunchPad Jumpers</b></span>
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<br>
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<ul>
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<li>Remove J16 J17 J18: Disconnects light sensor from the microcontroller PA22 PA27 PA26</li>
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<li>J5: Connects PB22 to blue LED2</li>
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<li>J6: Connects PB26 to red LED2</li>
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<li>J7: Connects PB27 to green LED2</li>
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</ul>
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</p> </td>
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</tr>
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</tbody>
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</table>
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</body>
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</html>
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<p>
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Simplified BSD License (FreeBSD License)
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Copyright © 2023, Jonathan Valvano, All rights reserved.<br>
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<br>
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:<br>
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<ol>
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<li>Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.</li>
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<li>Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.</li></ol>
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.<br>
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<br>
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The views and conclusions contained in the software and documentation are
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those of the authors and should not be interpreted as representing official
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policies, either expressed or implied, of the FreeBSD Project.
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<br>
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</p>
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<p>For more information, see <a href="http://users.ece.utexas.edu/~valvano/">
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http://users.ece.utexas.edu/~valvano/</a>.
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</p>
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</div>
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</body>
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</html>
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