Allow reconfig of radio, add getRSSI()

- Remove the `radioConfigured` variable so the radio will be reconfigured every time begin() is called like with RF24
- Add `getRSSI()` function
- remove `begin()` from `powerUp()` function, as users will typically call `begin()` afterward
- Set DPL to false in `begin()`, remove from `powerDown()` function.

src/nrf_to_nrf.cpp

@@ -70,7 +70,6 @@ nrf_to_nrf::nrf_to_nrf()
     ackPayloadsEnabled = false;
     ackPipe = 0;
     inRxMode = false;
-    radioConfigured = false;
     ARC = 0;
     addressWidth = 5;
     ackTimeout = ACK_TIMEOUT_1MBPS;
@@ -98,10 +97,6 @@ nrf_to_nrf::nrf_to_nrf()
 bool nrf_to_nrf::begin()
 {
 
-    if (radioConfigured) {
-        return 1;
-    }
-
     NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
     NRF_CLOCK->TASKS_HFCLKSTART = 1;
 
@@ -149,7 +144,7 @@ bool nrf_to_nrf::begin()
     NRF_RADIO->SHORTS = 1 << 19;
     NRF_RADIO->FREQUENCY = 0x4C;
 
-    radioConfigured = true;
+    DPL = false;
     return 1;
 }
 
@@ -1198,17 +1193,26 @@ bool nrf_to_nrf::testRPD(uint8_t RSSI)
 
 /**********************************************************************************************************/
 
+uint8_t nrf_to_nrf::getRSSI()
+{
+    NRF_RADIO->EVENTS_RSSIEND = 0;
+    NRF_RADIO->TASKS_RSSISTART = 1;
+    while (!NRF_RADIO->EVENTS_RSSIEND) {
+    }
+    return (uint8_t)NRF_RADIO->RSSISAMPLE;
+}
+
+/**********************************************************************************************************/
+
 void nrf_to_nrf::powerUp()
 {
-    radioConfigured = false;
-    begin();
+    NRF_RADIO->POWER = 1;
 }
 
 /**********************************************************************************************************/
 
 void nrf_to_nrf::powerDown()
 {
-    DPL = false;
     NRF_RADIO->POWER = 0;
 }
 

src/nrf_to_nrf.h

@@ -395,6 +395,13 @@ class nrf_to_nrf
      */
     bool testRPD(uint8_t RSSI = 65);
 
+    /**
+     * A new function specific to the NRF52x devices, not available on NRF24
+     * @return The function will return the RSSI, which is measured continuously and the value 
+     * filtered using a single-pole IIR filter. This is a negative value: received signal strength = -A dBm
+     */
+    uint8_t getRSSI();
+
     /**
      * Same as NRF24
      */
@@ -488,7 +495,6 @@ class nrf_to_nrf
     uint32_t rxPrefix;
     uint32_t txBase;
     uint32_t txPrefix;
-    bool radioConfigured;
     bool ackPayloadAvailable;
     uint8_t ackAvailablePipeNo;
     uint8_t lastPacketCounter;