Add powerUp to begin(), increase powerUp delay

- Found I could create a hang condition on startup with some code.
a: Now power up the radio on begin() to simplify things
b: Increase delay to 5ms for powerUp, although it should only take 2ms
tops, this prevents the hanging condition.

Author: TMRh20

RF24.cpp

@@ -399,6 +399,8 @@ void RF24::begin(void)
   flush_rx();
   flush_tx();
 
+  powerUp();
+  delay(5);
   //Enable PTX, do not write CE high so radio will remain in standby I mode ( 130us max to transition to RX or TX instead of 1500us from powerUp )
   write_register(CONFIG, ( read_register(CONFIG) ) & ~_BV(PRIM_RX) );
 
@@ -449,7 +451,7 @@ void RF24::powerDown(void)
 void RF24::powerUp(void)
 {
   write_register(CONFIG,read_register(CONFIG) | _BV(PWR_UP));
-  delay(2);
+  delay(5);
 }
 
 /******************************************************************/

RF24.h

@@ -996,6 +996,7 @@ class RF24
  * - Changes to read() functionality have increased reliability and response
  * - Extended timeout periods have been added to aid in noisy or otherwise unreliable environments
  * - Delays have been removed where possible to ensure maximum efficiency
+ * - Untested: Arduino Due and ATTiny 84/85 support: Do NOT #include <SPI.h> with ATTiny.
  * - More! See the links below and class documentation for more info.
  *
  * If issues are discovered with the documentation, please report them here: <a href="https://github.com/TMRh20/tmrh20.github.io/issues"> here</a>
@@ -1025,5 +1026,5 @@ class RF24
  */
 
 #endif // __RF24_H__
-// vim:ai:cin:sts=2 sw=2 ft=cpp
+