diff --git a/Makefile b/Makefile
index 78dc6c1b..4aac2aa5 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,7 @@ endif
 
 
 # Find first cross compilation tools
-XTOOLS_DIR = $(abspath $(shell dirname `${WHICH} arm-none-eabi-gcc`)/..)
+XTOOLS_DIR ?= $(abspath $(shell dirname `${WHICH} arm-none-eabi-gcc`)/..)
 
 # Set tool & Lib paths
 X_LIBC_DIR = $(XTOOLS_DIR)/arm-none-eabi/lib/armv7e-m/fpu
@@ -21,7 +21,7 @@ X_AR = $(XTOOLS_DIR)/bin/arm-none-eabi-ar
 X_LD = $(XTOOLS_DIR)/bin/arm-none-eabi-ld
 X_GDB = $(XTOOLS_DIR)/bin/arm-none-eabi-gdb
 
-OUT_DIR = debug
+OUT_DIR = build
 
 OUTPUT = grbl-stm32
 
diff --git a/STM32F103C8T6.ld b/STM32F103C8T6.ld
new file mode 100644
index 00000000..e352167d
--- /dev/null
+++ b/STM32F103C8T6.ld
@@ -0,0 +1,132 @@
+OUTPUT_FORMAT ("elf32-littlearm", "elf32-bigarm", "elf32-littlearm")
+/* Internal Memory Map*/
+MEMORY
+{
+	rom (rx)  : ORIGIN = 0x08000000, LENGTH = 0x00020000
+	ram (rwx) : ORIGIN = 0x20000000, LENGTH = 0x00005000
+}
+
+_eram = 0x20000000 + 0x00005000;
+SECTIONS
+{
+	.text :
+	{
+		KEEP(*(.isr_vector))
+		*(.text*)
+		
+		KEEP(*(.init))
+		KEEP(*(.fini))
+		
+		/* .ctors */
+		*crtbegin.o(.ctors)
+		*crtbegin?.o(.ctors)
+		*(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors)
+		*(SORT(.ctors.*))
+		*(.ctors)
+		
+		/* .dtors */
+		*crtbegin.o(.dtors)
+		*crtbegin?.o(.dtors)
+		*(EXCLUDE_FILE(*crtend?.o *crtend.o) .dtors)
+		*(SORT(.dtors.*))
+		*(.dtors)
+		
+		*(.rodata*)
+		
+		KEEP(*(.eh_fram e*))
+	} > rom 
+	
+	.ARM.extab : 
+	{
+		*(.ARM.extab* .gnu.linkonce.armextab.*)
+	} > rom 
+	
+	__exidx_start = .;
+	.ARM.exidx :
+	{
+		*(.ARM.exidx* .gnu.linkonce.armexidx.*)
+	} > rom 
+	__exidx_end = .;
+	__etext = .;
+	
+	/* _sidata is used in coide startup code */
+	_sidata = __etext;
+	
+	.data : AT (__etext)
+	{
+		__data_start__ = .;
+		
+		/* _sdata is used in coide startup code */
+		_sdata = __data_start__;
+		
+		*(vtable)
+		*(.data*)
+		
+		. = ALIGN(4);
+		/* preinit data */
+		PROVIDE_HIDDEN (__preinit_array_start = .);
+		KEEP(*(.preinit_array))
+		PROVIDE_HIDDEN (__preinit_array_end = .);
+		
+		. = ALIGN(4);
+		/* init data */
+		PROVIDE_HIDDEN (__init_array_start = .);
+		KEEP(*(SORT(.init_array.*)))
+		KEEP(*(.init_array))
+		PROVIDE_HIDDEN (__init_array_end = .);
+		
+		. = ALIGN(4);
+		/* finit data */
+		PROVIDE_HIDDEN (__fini_array_start = .);
+		KEEP(*(SORT(.fini_array.*)))
+		KEEP(*(.fini_array))
+		PROVIDE_HIDDEN (__fini_array_end = .);
+		
+		KEEP(*(.jcr*))
+		. = ALIGN(4);
+		/* All data end */
+		__data_end__ = .;
+		
+		/* _edata is used in coide startup code */
+		_edata = __data_end__;
+	} > ram 
+	
+	.bss :
+	{
+		. = ALIGN(4);
+		__bss_start__ = .;
+		_sbss = __bss_start__;
+		*(.bss*)
+		*(COMMON)
+		. = ALIGN(4);
+		__bss_end__ = .;
+		_ebss = __bss_end__;
+	} > ram 
+		
+	.heap (COPY):
+	{
+		__end__ = .;
+		_end = __end__;
+		end = __end__;
+		*(.heap*)
+		__HeapLimit = .;
+	} > ram 
+	
+	/* .stack_dummy section doesn't contains any symbols. It is only
+	* used for linker to calculate size of stack sections, and assign
+	* values to stack symbols later */
+	.co_stack (NOLOAD):
+	{
+		. = ALIGN(8);
+		*(.co_stack .co_stack.*)
+	} > ram 
+	
+	/* Set stack top to end of ram , and stack limit move down by
+	* size of stack_dummy section */
+	__StackTop = ORIGIN(ram ) + LENGTH(ram );
+	__StackLimit = __StackTop - SIZEOF(.co_stack);
+	PROVIDE(__stack = __StackTop);
+	
+	/* Check if data + heap + stack exceeds ram  limit */
+	ASSERT(__StackLimit >= __HeapLimit, "region ram  overflowed with stack")
+}
diff --git a/grbl/probe.c b/grbl/probe.c
index 985d5872..09996a88 100644
--- a/grbl/probe.c
+++ b/grbl/probe.c
@@ -22,7 +22,7 @@
 
 
 // Inverts the probe pin state depending on user settings and probing cycle mode.
-uint8_t probe_invert_mask;
+uint16_t probe_invert_mask;
 
 
 // Probe pin initialization routine.