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14<h1 align="left">MIC_StartLimitedSampling <img src="../../image/TWL.gif"></h1>
15
16<h2>Syntax</h2>
17<dl>
18  <dd>
19<CODE>#include &lt;twl/spi.h&gt;</CODE><BR>
20  <PRE><CODE><A href="MICResult.html">MICResult</A> MIC_StartLimitedSampling(
21            const <CODE><A href="MICAutoParam.html">MICAutoParam</A></CODE>*    param );</CODE></PRE>
22  </dd>
23</dl>
24
25<h2>Arguments</h2>
26<TABLE border="1" width="100%">
27  <TBODY>
28    <TR>
29<TD width="300"><SPAN class="argument">param</SPAN></TD>
30<TD width="700">Pointer to a <A href="MICAutoParam.html"><CODE>MICAutoParam</CODE></A>-type auto-sampling settings structure.</TD>
31    </TR>
32  </TBODY>
33</TABLE>
34
35<h2>Return Values</h2>
36<P>
37Returns the processing result as a <A href="MICResult.html"><CODE>MICResult</CODE></A> enumerated type. Returns <CODE>MIC_RESULT_SUCCESS</CODE> if processing completed successfully; returns some other value if the process failed.
38</P>
39
40<H2>Description</H2>
41<P>Starts frequency-limited microphone auto-sampling.<BR>Use the <A href="../pm/PM_SetAmp.html"><CODE>PM_SetAmp*</CODE></A> function to turn on the programmable gain amp before sampling.<BR>This function issues a request to the ARM7 to start frequency-limited auto-sampling, waits for the ARM7 to respond, and returns the processing result. This is a synchronous version of the <A href="MIC_StartLimitedSamplingAsync.html"><CODE>MIC_StartLimitedSamplingAsync</CODE></A> function. Where the input volume falls outside the minimum or maximum value, the sampling data is clamped.
42</P>
43<P>
44Frequency-limited auto-sampling differs from normal auto-sampling in that the hardware does the actual sampling. As a result, stable sampling can be performed at precise cycles; also, with the CPU burden on the ARM7 relaxed, effects of sampling on wireless communications and other I/O are reduced. On the other hand, sampling cannot be performed at frequencies that are unsupported by the hardware.  The following sampling frequencies can be specified for <SPAN class="argument">param</SPAN><CODE>-&gt;rate</CODE>, but the frequencies that can be specified at a given time depend on the sound master frequency settings and thus are further limited to four of the following. A value of <CODE>MIC_RESULT_ILLEGAL_PARAMETER</CODE> is returned if one of the limited frequencies is not specified.
45</P>
46<TABLE border="1" width="100%">
47  <TBODY>
48    <TR>
49<TH width="20%"><center>Sound Master Frequency</center></TD>
50<TH width="40%"><center>Settable Frequency</center></TD>
51<TH width="40%"><center>Description</center></TD>
52    </TR>
53    <TR>
54<TD rowspan="4">32.73 kHz</TD>
55<TD><CODE>MIC_SAMPLING_RATE_32730</CODE></TD>
56<TD>32.73 kHz (1/1 of the master frequency)</TD>
57    </TR>
58    <TR>
59<TD><CODE>MIC_SAMPLING_RATE_16360</CODE></TD>
60<TD>16.36 kHz (1/2 of the master frequency)</TD>
61    </TR>
62    <TR>
63<TD><CODE>MIC_SAMPLING_RATE_10910</CODE></TD>
64<TD>10.91 kHz (1/3 of the master frequency)</TD>
65    </TR>
66    <TR>
67<TD><CODE>MIC_SAMPLING_RATE_8180</CODE></TD>
68<TD>8.18 kHz (1/4 of the master frequency)</TD>
69    </TR>
70    <TR>
71<TD rowspan="4">47.61kHz</TD>
72<TD><CODE>MIC_SAMPLING_RATE_47610</CODE></TD>
73<TD>47.61 kHz (1/1 of the master frequency)</TD>
74    </TR>
75    <TR>
76<TD><CODE>MIC_SAMPLING_RATE_23810</CODE></TD>
77<TD>23.81 kHz (1/2 of the master frequency)</TD>
78    </TR>
79    <TR>
80<TD><CODE>MIC_SAMPLING_RATE_15870</CODE></TD>
81<TD>15.87 kHz (1/3 of the master frequency)</TD>
82    </TR>
83    <TR>
84<TD><CODE>MIC_SAMPLING_RATE_11900</CODE></TD>
85<TD>11.90 kHz (1/4 of the master frequency)</TD>
86    </TR>
87  </TBODY>
88</TABLE>
89
90<H2>Note</H2>
91<P>
92<FONT color=red>This function waits for a PXI interrupt for synchronization purposes. Do not call it when PXI interrupts are prohibited.<BR> <BR>Because frequency-limited auto-sampling cannot be performed on the NITRO platform or when the CODEC is running in CODEC-DS mode, this function instead calls the <A href="MIC_StartAutoSampling.html"><CODE>MIC_StartAutoSampling</CODE></A> auto-sampling control function.</FONT>
93</P>
94<P><FONT color=red>It has been confirmed that slight hardware noise is mixed with the microphone input on the TWL system. See <A href="./about_HardwareNoise.html">here</A> for a workaround.</FONT></P>
95<H2>See Also</H2>
96<P>
97<A href="MIC_StartLimitedSamplingAsync.html"><CODE>MIC_StartLimitedSamplingAsync</CODE></A><BR> <A href="MIC_StopLimitedSampling.html"><CODE>MIC_StopLimitedSampling</CODE></A><BR> <A href="MIC_AdjustLimitedSampling.html"><CODE>MIC_AdjustLimitedSampling</CODE></A>
98</P>
99
100<H2>Revision History</H2>
101<P>
1022009/06/25 Added description of using the <CODE>PM_SetAmp*</CODE> function.<BR> 2008/01/09 Added a note about the difference in behavior with CODEC mode.<BR> 2007/11/17 Initial version.
103</P>
104<hr><p>CONFIDENTIAL</p></body>
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