Working version. Tested on linux PC.

platformio.ini

@@ -12,4 +12,7 @@
 platform = teensy
 board = teensy40
 framework = arduino
-build_flags = -D USB_FLIGHTSIM_JOYSTICK
+build_flags = -D USB_HID
+lib_deps = 
+	contrem/arduino-timer@^3.0.1
+	thomasfredericks/Bounce2@^2.72

src/defines.h

@@ -0,0 +1,9 @@
+//Define pins used for each gear
+#define GEAR1 1
+#define GEAR2 2
+#define GEAR3 3
+#define GEAR4 4
+#define GEAR5 5
+#define GEAR6 6
+
+#define NUM_BUTTONS 6

src/main.cpp

@@ -1,18 +1,41 @@
-#include <Arduino.h>
+#include "defines.h"
 
-// put function declarations here:
+#include <Arduino.h>
-int myFunction(int, int);
+#include <arduino-timer.h>
+#include <Bounce2.h>
+#include <usb_joystick.h>
+
+Timer<1, micros> TxTimer;
+Bounce2::Button * buttons = new Bounce2::Button[NUM_BUTTONS];
+const uint8_t BUTTON_PINS[NUM_BUTTONS] = {GEAR1, GEAR2, GEAR3, GEAR4, GEAR5, GEAR6};
+
+bool TxJoystick(void *) {
+  Joystick.send_now();
+  return true;
+}
 
 void setup() {
-  // put your setup code here, to run once:
+  //Enable manual send of joystick packets
-  int result = myFunction(2, 3);
+  Joystick.useManualSend(true);
+
+  //Attach buttons to debounce library. pullup, pressed state is low
+  for (int i = 0; i < NUM_BUTTONS; i++) {
+    buttons[i].attach( BUTTON_PINS[i] , INPUT_PULLUP  );  //setup the bounce instance for the current button
+    buttons[i].interval(5);  // interval in ms
+    buttons[i].setPressedState(LOW);
+  }
+
+  TxTimer.every(1000, TxJoystick);
 }
 
 void loop() {
-  // put your main code here, to run repeatedly:
+  //Read buttons and update joystick state.
+  for (int i = 0; i < NUM_BUTTONS; i++) {
+    buttons[i].update();
+    Joystick.button(i+1, buttons[i].isPressed());
   }
   
-// put function definitions here:
+  //Transmit USB packet
-int myFunction(int x, int y) {
+  TxTimer.tick();
-  return x + y;
+
 }