diff --git a/App/CMakeLists.txt b/App/CMakeLists.txt
index a3016818..ff065bdb 100644
--- a/App/CMakeLists.txt
+++ b/App/CMakeLists.txt
@@ -95,8 +95,7 @@ if(ENABLE_AIRCOPY OR ENABLE_UART OR ENABLE_USB)
 endif()
 
 enable_feature(ENABLE_UART
-    driver/uart.c 
-    app/uart.c
+    driver/uart.c
     # driver/aes.c
 )
 
@@ -177,6 +176,14 @@ enable_feature(ENABLE_EXTRA_UART_CMD)
 
 # ---- F4HWN MODS ----
 
+if(NOT ENABLE_UART AND NOT ENABLE_USB)
+    if(ENABLE_FEAT_F4HWN_K5VIEWER OR ENABLE_FEAT_F4HWN_RXTX_LOG_K5VIEWER)
+        message(STATUS "Disabling K5Viewer because both ENABLE_UART and ENABLE_USB are OFF.")
+    endif()
+    set(ENABLE_FEAT_F4HWN_K5VIEWER OFF)
+    set(ENABLE_FEAT_F4HWN_RXTX_LOG_K5VIEWER OFF)
+endif()
+
 enable_feature(ENABLE_FEAT_F4HWN)
 enable_feature(ENABLE_FEAT_F4HWN_GAME 
     app/breakout.c
diff --git a/App/app/app.c b/App/app/app.c
index 5165646f..dddf1076 100644
--- a/App/app/app.c
+++ b/App/app/app.c
@@ -1654,7 +1654,9 @@ void APP_TimeSlice10ms(void)
     }
 
 #ifdef ENABLE_FEAT_F4HWN_LOGO_SAV
+#ifdef ENABLE_FEAT_F4HWN_K5VIEWER
     bool screenSaverRendered = false;
+#endif
 
     if (gScreenSaverDisplayed) {
         if (gUpdateDisplayCurrent) {
@@ -1668,13 +1670,17 @@ void APP_TimeSlice10ms(void)
             if (++gScreenSaverTick >= 8u) {
                 gScreenSaverTick = 0;
                 ScreenSaverRenderMatrix(false);
+#ifdef ENABLE_FEAT_F4HWN_K5VIEWER
                 screenSaverRendered = true;
+#endif
             }
         } else if (gSetting_set_sav == SET_SAV_LOGO_PLUS) {
             if (++gScreenSaverTick >= 16u) {
                 gScreenSaverTick = 0;
                 ScreenSaverRenderLogoPlus(false);
+#ifdef ENABLE_FEAT_F4HWN_K5VIEWER
                 screenSaverRendered = true;
+#endif
             }
         }
     }
diff --git a/App/app/uart.c b/App/app/uart.c
index 177666b5..db9b8994 100644
--- a/App/app/uart.c
+++ b/App/app/uart.c
@@ -260,6 +260,7 @@ static void SendReply(uint32_t Port, void *pReply, uint16_t Size)
     }
 #endif
 
+#if defined(ENABLE_UART)
     Header_t Header;
     Footer_t Footer;
 
@@ -290,6 +291,7 @@ static void SendReply(uint32_t Port, void *pReply, uint16_t Size)
     Footer.ID = 0xBADC;
 
     UART_Send(&Footer, sizeof(Footer));
+#endif
 }
 
 static void SendVersion(uint32_t Port)
diff --git a/App/k5viewer.c b/App/k5viewer.c
index 5752ad34..2167dc40 100644
--- a/App/k5viewer.c
+++ b/App/k5viewer.c
@@ -18,7 +18,12 @@
 #include "driver/st7565.h"
 #include "k5viewer.h"
 #include "misc.h"
+#ifdef ENABLE_UART
+#include "driver/uart.h"
+#endif
+#ifdef ENABLE_USB
 #include "driver/vcp.h"
+#endif
 #include "driver/keyboard.h"
 #include "driver/bk4819.h"
 #ifdef ENABLE_FEAT_F4HWN_RXTX_LOG_K5VIEWER
@@ -67,26 +72,41 @@ void K5VIEWER_ParseInput(void)
     if (K5VIEWER_IsLocked())
         return;
 
+#ifdef ENABLE_UART
     if (UART_IsCableConnected()) {
         keepAlive = 15;
         hasConnectionPing = true;
         gUSB_K5ViewerEnabled = false;
+        return;
     }
-    else if (VCP_K5ViewerPing()) {
+#endif
+
+#ifdef ENABLE_USB
+    if (VCP_K5ViewerPing()) {
         keepAlive = 15;
         hasConnectionPing = true;
         gUSB_K5ViewerEnabled = true;
     }
+#endif
 
 }
 
 static void K5VIEWER_Send(const uint8_t *buf, uint16_t len)
 {
+#if defined(ENABLE_UART) && defined(ENABLE_USB)
     if (gUSB_K5ViewerEnabled) {
         cdc_acm_data_send_with_dtr(buf, len);
     } else {
         UART_Send(buf, len);
     }
+#elif defined(ENABLE_USB)
+    cdc_acm_data_send_with_dtr(buf, len);
+#elif defined(ENABLE_UART)
+    UART_Send(buf, len);
+#else
+    (void)buf;
+    (void)len;
+#endif
 }
 
 enum {