SPRACINGF3NEO - Use RTC6705 clk hack.

CF/BF - Fix typo in max7456DmaInProgress.  Always define an
implementation even when there is no TX-DMA.

CF/BF - Ensure that max7456 communication does not disrupt RTC6705
communication when using the same SPI port for both.

CF/BF - Port RTC6705 to use the VTX API.

* Support VTX channel/band/power on OSD for ALL vtx APIs - previously it only supported RTC6705.
* Remove all FEATURE_VTX usage.
* Remove all `#define VTX` usage.

Note that due to the async nature of tramp/smartaudio it's not possible
to know the current band/channel after requesting a change (as the
request hasn't been processed) so it makes no sense to try and save the
config - and on the tramp/smartaudio vtx the vtx maintains it's state.
So on an RTX6705 equipped FC the user should now MANUALLY save the
config using the save config stick position.

CF/BF - Move CMS for RTC6705 into vtx_rtc6705.c for consistency with
other VTX CMS menus.

CF/BF - Update RTC6705 via SOFT SPI to use VTX API.

* Achieved by simply aligning the API at the driver level and removing
all legacy conditional compilation checks.

CF/BF - Use new IO for RTC6705 CLK Hack

CF/BF - Port VTX button from CF v1.x.

Features:
* Channel Cycle
* Band Cycle
* Power Cycle
* Save Settings
* Works with any VTX using VTX API.

CF/BF - Allow support for Internal and External VTX - External takes
precedence when configured.

CF/BF - Fix display of VTX power in CMS.

* Issue occured when CMS was transitioned from integer to list of
strings.

CF/BF - Disable SMARTAUDIO and TRAMP on the SPRacingF3NEO due to flash
size.

CF/BF - Cleanup const usage of bass-by-value parameters.  Cleanup
naming.

CF/BF - Cleanup naming.  Removing noise-words. Improving consistency.

CF/BF - Improve readability by further naming cleanups.

CF/BF - Remove some magic numbers in the RTC6705 VTX code.

CF/BF - Use braces on some procedural macros.

CF/BF - Improve code readability by renaming rtc6705SetChannel to
rtc6705SetBandAndChannel.

CF/BF - Remove editor mishap.

CF/BF - Make the rtc6705Dev variable static.

CF/BF - remove duplicate state variablertc6705Dev_t - vtxDevice_t had
all we needed.  Use brackets on some procedural style macros.  Make all
the vtx vtable static const.

CF/BF - making some declarations const.

CF/BF - Fix vtx_power maximum value (out by one).

src/main/fc/fc_init.c

@@ -55,6 +55,7 @@
 #include "drivers/adc.h"
 #include "drivers/bus_i2c.h"
 #include "drivers/bus_spi.h"
+#include "drivers/buttons.h"
 #include "drivers/inverter.h"
 #include "drivers/flash_m25p16.h"
 #include "drivers/sonar_hcsr04.h"
@@ -62,7 +63,9 @@
 #include "drivers/usb_io.h"
 #include "drivers/transponder_ir.h"
 #include "drivers/exti.h"
-#include "drivers/vtx_soft_spi_rtc6705.h"
+#include "drivers/max7456.h"
+#include "drivers/vtx_rtc6705.h"
+#include "drivers/vtx_common.h"
 
 #include "fc/config.h"
 #include "fc/fc_init.h"
@@ -92,7 +95,8 @@
 #include "io/osd.h"
 #include "io/osd_slave.h"
 #include "io/displayport_msp.h"
-#include "io/vtx.h"
+#include "io/vtx_rtc6705.h"
+#include "io/vtx_control.h"
 #include "io/vtx_smartaudio.h"
 #include "io/vtx_tramp.h"
 
@@ -156,6 +160,18 @@ void processLoopback(void)
 }
 
 
+#ifdef VTX_RTC6705
+bool canUpdateVTX(void)
+{
+#if defined(MAX7456_SPI_INSTANCE) && defined(RTC6705_SPI_INSTANCE) && defined(SPI_SHARED_MAX7456_AND_RTC6705)
+    if (feature(FEATURE_OSD)) {
+        return !max7456DmaInProgress();
+    }
+#endif
+    return true;
+}
+#endif
+
 #ifdef BUS_SWITCH_PIN
 void busSwitchInit(void)
 {
@@ -217,17 +233,8 @@ void init(void)
 #endif
 
 #if defined(BUTTONS)
-#ifdef BUTTON_A_PIN
-    IO_t buttonAPin = IOGetByTag(IO_TAG(BUTTON_A_PIN));
-    IOInit(buttonAPin, OWNER_SYSTEM, 0);
-    IOConfigGPIO(buttonAPin, IOCFG_IPU);
-#endif
 
-#ifdef BUTTON_B_PIN
-    IO_t buttonBPin = IOGetByTag(IO_TAG(BUTTON_B_PIN));
-    IOInit(buttonBPin, OWNER_SYSTEM, 0);
-    IOConfigGPIO(buttonBPin, IOCFG_IPU);
-#endif
+    buttonsInit();
 
     // Check status of bind plug and exit if not active
     delayMicroseconds(10);  // allow configuration to settle
@@ -238,7 +245,7 @@ void init(void)
         uint8_t secondsRemaining = 5;
         bool bothButtonsHeld;
         do {
-            bothButtonsHeld = !IORead(buttonAPin) && !IORead(buttonBPin);
+            bothButtonsHeld = buttonAPressed() && buttonBPressed();
             if (bothButtonsHeld) {
                 if (--secondsRemaining == 0) {
                     resetEEPROM();
@@ -375,8 +382,8 @@ void init(void)
     updateHardwareRevision();
 #endif
 
-#ifdef VTX
-    vtxInit();
+#ifdef VTX_RTC6705
+    rtc6705IOInit();
 #endif
 
 #if defined(SONAR_SOFTSERIAL2_EXCLUSIVE) && defined(SONAR) && defined(USE_SOFTSERIAL2)
@@ -439,19 +446,6 @@ void init(void)
 
     rxInit();
 
-/*
- * VTX
- */
-
-#ifdef USE_RTC6705
-    if (feature(FEATURE_VTX)) {
-        rtc6705_soft_spi_init();
-        current_vtx_channel = vtxConfig()->vtx_channel;
-        rtc6705_soft_spi_set_channel(vtx_freq[current_vtx_channel]);
-        rtc6705_soft_spi_set_rf_power(vtxConfig()->vtx_power);
-    }
-#endif
-
 /*
  * CMS, display devices and OSD
  */
@@ -568,13 +562,25 @@ void init(void)
 #endif
 
 #ifdef VTX_CONTROL
+    vtxControlInit();
+
+    vtxCommonInit();
 
 #ifdef VTX_SMARTAUDIO
-    smartAudioInit();
+    vtxSmartAudioInit();
 #endif
 
 #ifdef VTX_TRAMP
-    trampInit();
+    vtxTrampInit();
+#endif
+
+#ifdef VTX_RTC6705
+#ifdef VTX_RTC6705OPTIONAL
+    if (!vtxCommonDeviceRegistered()) // external VTX takes precedence when configured.
+#endif
+    {
+        vtxRTC6705Init();
+    }
 #endif
 
 #endif // VTX_CONTROL