Fix RF switching logic on rp2040-lora board. (#4486)

* Fix LED pinout for T-Echo board marked v1.0, date 2021-6-28

* Merge PR #420

* Fixed double and missing Default class.

* Use correct format specifier and fixed typo.

* Removed duplicate code.

* Fix error: #if with no expression

* Fix warning: extra tokens at end of #endif directive.

* Fix antenna switching logic. Complementary-pin control logic is required on the rp2040-lora board.

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

variants/rp2040-lora/variant.h

@@ -15,7 +15,7 @@
 // rxd = 9
 
 #define EXT_NOTIFY_OUT 22
-#define BUTTON_PIN 17
+#undef BUTTON_PIN // Pin 17 used for antenna switching via DIO4
 
 #define LED_PIN PIN_LED
 
@@ -32,23 +32,28 @@
 
 // https://www.waveshare.com/rp2040-lora.htm
 // https://www.waveshare.com/img/devkit/RP2040-LoRa-HF/RP2040-LoRa-HF-details-11.jpg
-#define LORA_SCK 14  // 10
-#define LORA_MISO 24 // 12
-#define LORA_MOSI 15 // 11
-#define LORA_CS 13   // 3
+#define LORA_SCK 14  // GPIO14
+#define LORA_MISO 24 // GPIO24
+#define LORA_MOSI 15 // GPIO15
+#define LORA_CS 13   // GPIO13
 
-#define LORA_DIO0 RADIOLIB_NC
-#define LORA_RESET 23 // 15
-#define LORA_DIO1 16  // 20
-#define LORA_DIO2 18  // 2
-#define LORA_DIO3 RADIOLIB_NC
-#define LORA_DIO4 17
+#define LORA_DIO0 RADIOLIB_NC // No GPIO connection
+#define LORA_RESET 23         // GPIO23
+#define LORA_BUSY 18          // GPIO18
+#define LORA_DIO1 16          // GPIO16
+#define LORA_DIO2 RADIOLIB_NC // Antenna switching, no GPIO connection
+#define LORA_DIO3 RADIOLIB_NC // No GPIO connection
+#define LORA_DIO4 17          // GPIO17
+
+// On rp2040-lora board the antenna switch is wired and works with complementary-pin control logic.
+// See PE4259 datasheet page 4
 
 #ifdef USE_SX1262
 #define SX126X_CS LORA_CS
 #define SX126X_DIO1 LORA_DIO1
-#define SX126X_BUSY LORA_DIO2
+#define SX126X_BUSY LORA_BUSY
 #define SX126X_RESET LORA_RESET
-#define SX126X_DIO2_AS_RF_SWITCH
+#define SX126X_DIO2_AS_RF_SWITCH // Antenna switch CTRL
+#define SX126X_RXEN LORA_DIO4    // Antenna switch !CTRL via GPIO17
 // #define SX126X_DIO3_TCXO_VOLTAGE 1.8
 #endif