Add H8I8O and H8C09 configurations to knx-demo

Addressing #181

These configurations both serve as examples for the use of these boards and other custom boards that don't use the standard pinout.

examples/knx-demo/platformio.ini

@@ -100,3 +100,46 @@ lib_deps =
 build_flags =
   -DMASK_VERSION=0x07B0
   -Wno-unknown-pragmas
+
+;--- STM32/GD32 ---
+[env:h8i8o]
+platform = ststm32
+board = genericSTM32F103CB
+framework = arduino
+; We consider that the this projects is opened within its project directory
+; while working with VS Code.
+lib_extra_dirs = ../../../
+
+lib_deps =
+  knx
+
+build_flags =
+  -DENABLE_HWSERIAL1
+  -DPIN_SERIAL1_TX=PA9
+  -DPIN_SERIAL1_RX=PA10
+  -DKNX_SERIAL=Serial1
+  -DKNX_BUTTON=PA11
+  -DKNX_LED=PA12
+  -DMASK_VERSION=0x07B0
+  -Wno-unknown-pragmas
+
+[env:h8c09]
+platform = ststm32
+board = genericSTM32F103CB
+framework = arduino
+; We consider that the this projects is opened within its project directory
+; while working with VS Code.
+lib_extra_dirs = ../../../
+
+lib_deps =
+  knx
+
+build_flags =
+  -DENABLE_HWSERIAL1
+  -DPIN_SERIAL1_TX=PA9
+  -DPIN_SERIAL1_RX=PA10
+  -DKNX_SERIAL=Serial1
+  -DKNX_BUTTON=PB0
+  -DKNX_LED=PB5
+  -DMASK_VERSION=0x07B0
+  -Wno-unknown-pragmas