Nrf24 lowlevel (#1192)

* Implemented nRF24 constant carrier wave

For testing purposes only! Not used by regular MySensors stack.

* Please Jenkins for unused functions

* Add RPD retrieval

Author: Yveaux

drivers/RF24/RF24.cpp

@@ -432,6 +432,13 @@ LOCAL void RF24_disableConstantCarrierWave(void)
 	RF24_setRFSetup(RF24_RF_SETUP);
 }
 
+LOCAL bool RF24_getReceivedPowerDetector(void)
+{
+	// nRF24L01+ only. nRF24L01 contains a carrier detect function (same register & bit) which works
+	// slightly different and takes at least 128us to become active.
+	return (RF24_readByteRegister(RF24_REG_RPD) & _BV(RF24_RPD)) != 0;
+}
+
 #if defined(MY_RX_MESSAGE_BUFFER_FEATURE)
 LOCAL void RF24_irqHandler(void)
 {

drivers/RF24/RF24.h

@@ -400,7 +400,11 @@ LOCAL void RF24_enableConstantCarrierWave(void) __attribute__((unused));
 * @brief Stop generating a constant carrier wave (for testing only).
 */
 LOCAL void RF24_disableConstantCarrierWave(void) __attribute__((unused));
-
+/**
+* @brief Retrieve latched RPD power level, in receive mode (for testing, nRF24L01+ only).
+* @return True when power level >-64dBm for more than 40us.
+*/
+LOCAL bool RF24_getReceivedPowerDetector(void) __attribute__((unused));
 
 #if defined(MY_RX_MESSAGE_BUFFER_FEATURE)
 /**

drivers/RF24/RF24registers.h

@@ -56,7 +56,8 @@
 #define RF24_REG_RF_SETUP		(0x06)
 #define RF24_REG_STATUS			(0x07)
 #define RF24_REG_OBSERVE_TX		(0x08)
-#define RF24_REG_CD				(0x09)
+#define RF24_REG_RPD			(0x09)          // nRF24L01+
+#define RF24_REG_CD				(RF24_REG_RPD)  // nRF24L01
 #define RF24_REG_RX_ADDR_P0		(0x0A)
 #define RF24_REG_RX_ADDR_P1		(0x0B)
 #define RF24_REG_RX_ADDR_P2		(0x0C)
@@ -79,7 +80,6 @@
 
 // instructions
 #define RF24_CMD_READ_REGISTER				(0x00)
-#define RF24_CMD_RPD						(0x09)
 #define RF24_CMD_WRITE_REGISTER				(0x20)
 #define RF24_CMD_ACTIVATE					(0x50)
 #define RF24_CMD_READ_RX_PL_WID				(0x60)
@@ -144,6 +144,8 @@
 #define RF24_TX_EMPTY		(4)
 #define RF24_RX_FULL		(1)
 #define RF24_RX_EMPTY		(0)
+#define RF24_RPD    		(0)         // nRF24L01+
+#define RF24_CD     		(RF24_RPD)  // nRF24L01
 
 // features
 #define RF24_EN_DPL			(2)