- removed default / fallback variant; you are forced to define the variant of your choice now or build will stop with an error

- added condition in config.h to either take setting from platform.ini or config.h
- homogenized default_envs naming; all variants now have VARIANT_ as prefix
- added nunchuck variant in platform.ini and config.h
- added PPM variant in platform.ini and config.h
- README: added jan's nunchuck breakout board repo

platformio.ini

@@ -6,10 +6,13 @@ include_dir = Inc
 src_dir     = Src
 
 ;=================== VARIANT SELECTION ==========================
-default_envs = VARIANT_ADC         ; Variant for control via ADC input
+default_envs = UNDEFINED            ; 
+;default_envs = VARIANT_ADC         ; Variant for control via ADC input
 ;default_envs = VARIANT_USART3      ; Variant for Serial control via USART3 input
-;default_envs = HOVERCAR            ; Variant for HOVERCAR build
-;default_envs = TRANSPOTTER         ; Variant for TRANSPOTTER build https://github.com/NiklasFauth/hoverboard-firmware-hack/wiki/Build-Instruction:-TranspOtter https://hackaday.io/project/161891-transpotter-ng
+;default_envs = VARIANT_HOVERCAR    ; Variant for HOVERCAR build
+;default_envs = VARIANT_TRANSPOTTER ; Variant for TRANSPOTTER build https://github.com/NiklasFauth/hoverboard-firmware-hack/wiki/Build-Instruction:-TranspOtter https://hackaday.io/project/161891-transpotter-ng
+;default_envs = VARIANT_NUNCHUCK    ; Variant for Nunchuck controlled vehicle build
+;default_envs = VARIANT_PPM         ; Variant for RC-Remotes with PPM-Sum signal
 ;================================================================
 
 [env:VARIANT_ADC]
@@ -33,6 +36,7 @@ build_flags =
     -g -ggdb        ; to generate correctly the 'firmware.elf' for STM STUDIO vizualization
 #    -Wl,-lnosys
     -D VARIANT_ADC
+    -D PALTFORMIO
 
 [env:VARIANT_USART3]
 platform        = ststm32
@@ -55,8 +59,9 @@ build_flags =
     -g -ggdb        ; to generate correctly the 'firmware.elf' for STM STUDIO vizualization
 #    -Wl,-lnosys
     -D VARIANT_USART3
+    -D PALTFORMIO
 
-[env:HOVERCAR]
+[env:VARIANT_HOVERCAR]
 platform        = ststm32
 framework       = stm32cube
 board           = genericSTM32F103RC
@@ -76,9 +81,10 @@ build_flags =
     -Wl,-lm
     -g -ggdb        ; to generate correctly the 'firmware.elf' for STM STUDIO vizualization
 #    -Wl,-lnosys
-    -D HOVERCAR
+    -D VARIANT_HOVERCAR
+    -D PALTFORMIO
 
-[env:TRANSPOTTER]
+[env:VARIANT_TRANSPOTTER]
 platform        = ststm32
 framework       = stm32cube
 board           = genericSTM32F103RC
@@ -94,4 +100,43 @@ build_flags =
     -Wl,-lm
     -g -ggdb        ; to generate correctly the 'firmware.elf' for STM STUDIO vizualization
 #    -Wl,-lnosys
-    -D TRANSPOTTER
+    -D VARIANT_TRANSPOTTER
+    -D PALTFORMIO
+
+[env:VARIANT_NUNCHUCK]
+platform        = ststm32
+framework       = stm32cube
+board           = genericSTM32F103RC
+debug_tool      = stlink
+upload_protocol = stlink
+
+build_flags =
+    -I${PROJECT_DIR}/inc/
+    -DUSE_HAL_DRIVER
+    -DSTM32F103xE
+    -Wl,-T./STM32F103RCTx_FLASH.ld
+    -Wl,-lc
+    -Wl,-lm
+    -g -ggdb        ; to generate correctly the 'firmware.elf' for STM STUDIO vizualization
+#    -Wl,-lnosys
+    -D VARIANT_NUNCHUCK
+    -D PALTFORMIO
+
+[env:VARIANT_PPM]
+platform        = ststm32
+framework       = stm32cube
+board           = genericSTM32F103RC
+debug_tool      = stlink
+upload_protocol = stlink
+
+build_flags =
+    -I${PROJECT_DIR}/inc/
+    -DUSE_HAL_DRIVER
+    -DSTM32F103xE
+    -Wl,-T./STM32F103RCTx_FLASH.ld
+    -Wl,-lc
+    -Wl,-lm
+    -g -ggdb        ; to generate correctly the 'firmware.elf' for STM STUDIO vizualization
+#    -Wl,-lnosys
+    -D VARIANT_PPM
+    -D PALTFORMIO