add TCXO option in Transmit Interrupts example

Case DIO3 with TCXO, setTCXO.

examples/SX126x/SX126x_Transmit_Interrupt/SX126x_Transmit_Interrupt.ino

@@ -40,6 +40,28 @@ void setup() {
     while (true);
   }
 
+  // NOTE: Some SX126x modules use TCXO
+  //       (Temprature-Compensated Crystal Oscillator).
+  //       To be able to use these modules, TCXO
+  //       control must be enabled by calling
+  //       setTCXO() and specifying the reference
+  //       voltage.
+  
+  /*
+    Serial.print(F("[SX1262] Setting TCXO reference ... "));
+    // enable TCXO
+    // reference voltage:           1.6 V
+    // timeout:                     5000 us
+    state = lora.setTCXO(1.6);
+    if (state == ERR_NONE) {
+      Serial.println(F("success!"));
+    } else {
+      Serial.print(F("failed, code "));
+      Serial.println(state);
+      while (true);
+    }
+  */
+   
   // set the function that will be called
   // when packet transmission is finished
   lora.setDio1Action(setFlag);