user15630: As in this SO question, I use use a RH_RF24.h to control an SI4463. In RH_RF24, there is not anything about the speed of communication. I need the way to control the speed of communication. Because I want to take high speed of communication when Rssi is strong and slow speed when weak (for reliability).
How should I to do it ?

user24169: According to RH_RF24.h setModemRegisters takes a ModemConfig struct.  prop_2003, prop_2004 and prop2005 are part of that struct and it's the value of these 3 bytes that sets the datarate.
Datarate is a 24bit unsigned value (hence the 3 bytes in the struct). prop_2003 is the MSB and prop_2005 the LSB.

prop_2003 default is 0x0F
prop_2004 default is 0x42
prop_2005 default is 0x40

meaning the default data rate is 0x0F4240 ( = 1Mbps)
This application note on the API gives more details (around page 99).

15630: <p>As in this <a href="https://arduino.stackexchange.com/q/31064/28084">SO question</a>, I use use a <a href="http://www.airspayce.com/mikem/arduino/RadioHead/classRH__RF24.html" rel="nofollow noreferrer">RH_RF24.h</a> to control an <a href="https://www.silabs.com/products/wireless/EZRadioPRO/Pages/Si446x.aspx" rel="nofollow noreferrer">SI4463</a>. In RH_RF24, there is not anything about the speed of communication. I need the way to control the speed of communication. Because I want to take high speed of communication when Rssi is strong and slow speed when weak (for reliability).</p>

<p>How should I to do it ?</p>
 24169: <p>According to <a href="http://www.airspayce.com/mikem/arduino/RadioHead/classRH__RF24.html" rel="nofollow">RH_RF24.h</a> <code>setModemRegisters</code> takes a <code>ModemConfig</code> struct.  <code>prop_2003</code>, <code>prop_2004</code> and <code>prop2005</code> are part of that struct and it's the value of these 3 bytes that sets the datarate.</p>

<p>Datarate is a <strong>24bit unsigned value</strong> (hence the 3 bytes in the struct). <code>prop_2003</code> is the <strong>MSB</strong> and <code>prop_2005</code> the <strong>LSB</strong>.</p>

<ul>
<li><code>prop_2003</code> default is <code>0x0F</code></li>
<li><code>prop_2004</code> default is <code>0x42</code></li>
<li><code>prop_2005</code> default is <code>0x40</code></li>
</ul>

<p>meaning the default data rate is <code>0x0F4240</code> ( = 1Mbps)</p>

<p><a href="http://community.silabs.com/mgrfq63796/attachments/mgrfq63796/BluetoothandWiFi/8086/1/Si446X%20API%20DESCRIPTIONS.pdf" rel="nofollow">This application note</a> on the API gives more details (around page 99).</p>
