Hello, I'm currently working on a project(STM32f4) which uses a chibios and ugfx library and i have a problem reading from a file. When i use a method gfileOpen() it always returns zero(NULL). I've added all necessary define statements into a gfxconf.h config file(#define GFX_USE_OS_CHIBIOS TRUE, #define GFX_USE_GFILE TRUE, #define GFILE_NEED_FATFS TRUE and #define GFILE_NEED_NOAUTOMOUNT FALSE) and i've also enabled a SDC subsystem in a halconf.h config file(#define HAL_USE_SDC TRUE). Here is my test code:  #include "gfx.h"  GFILE *file;  long length = -1;  int main(void) {      gfxInit();      file = gfileOpen("test.txt", "r");      if(file != NULL){        length = gfileGetSize(file);      }      while(1) {        gfxSleepMilliseconds(1000);      }      return 0; }  Here is my makefile:  ############################################################################## # Build global options # NOTE: Can be overridden externally. #  # Compiler options here. ifeq ($(USE_OPT),)   USE_OPT = -O2 -ggdb -fomit-frame-pointer -falign-functions=16 endif  # C specific options here (added to USE_OPT). ifeq ($(USE_COPT),)   USE_COPT =  endif  # C++ specific options here (added to USE_OPT). ifeq ($(USE_CPPOPT),)   USE_CPPOPT = -fno-rtti endif  # Enable this if you want the linker to remove unused code and data ifeq ($(USE_LINK_GC),)   USE_LINK_GC = yes endif  # Linker extra options here. ifeq ($(USE_LDOPT),)   USE_LDOPT =  endif  # Enable this if you want link time optimizations (LTO) ifeq ($(USE_LTO),)   USE_LTO = no endif  # If enabled, this option allows to compile the application in THUMB mode. ifeq ($(USE_THUMB),)   USE_THUMB = yes endif  # Enable this if you want to see the full log while compiling. ifeq ($(USE_VERBOSE_COMPILE),)   USE_VERBOSE_COMPILE = no endif  # # Build global options ##############################################################################  ############################################################################## # Architecture or project specific options #  # Enables the use of FPU on Cortex-M4 (no, softfp, hard). ifeq ($(USE_FPU),)   USE_FPU = no endif  # # Architecture or project specific options ##############################################################################  ############################################################################## # Project, sources and paths #  # Define project name here PROJECT = ch  # Imported source files and paths CHIBIOS = ../../chibios GFXLIB = ../../ugfx include $(CHIBIOS)/boards/ST_STM32F4_DISCOVERY/board.mk include $(CHIBIOS)/os/hal/platforms/STM32F4xx/platform.mk include $(CHIBIOS)/os/hal/hal.mk include $(CHIBIOS)/os/ports/GCC/ARMCMx/STM32F4xx/port.mk include $(CHIBIOS)/os/kernel/kernel.mk include $(GFXLIB)/gfx.mk include $(GFXLIB)/boards/base/STM32F407/board.mk       # board  # Define linker script file here LDSCRIPT= $(PORTLD)/STM32F407xG.ld #LDSCRIPT= $(PORTLD)/STM32F407xG_CCM.ld  # C sources that can be compiled in ARM or THUMB mode depending on the global # setting. CSRC = $(PORTSRC) \        $(KERNSRC) \        $(TESTSRC) \        $(HALSRC) \        $(PLATFORMSRC) \        $(BOARDSRC) \        $(GFXSRC) \        $(CHIBIOS)/os/various/devices_lib/accel/lis302dl.c \        $(CHIBIOS)/os/various/chprintf.c \        main.c  # C++ sources that can be compiled in ARM or THUMB mode depending on the global # setting. CPPSRC =  # C sources to be compiled in ARM mode regardless of the global setting. # NOTE: Mixing ARM and THUMB mode enables the -mthumb-interwork compiler #       option that results in lower performance and larger code size. ACSRC =  # C++ sources to be compiled in ARM mode regardless of the global setting. # NOTE: Mixing ARM and THUMB mode enables the -mthumb-interwork compiler #       option that results in lower performance and larger code size. ACPPSRC =  # C sources to be compiled in THUMB mode regardless of the global setting. # NOTE: Mixing ARM and THUMB mode enables the -mthumb-interwork compiler #       option that results in lower performance and larger code size. TCSRC =  # C sources to be compiled in THUMB mode regardless of the global setting. # NOTE: Mixing ARM and THUMB mode enables the -mthumb-interwork compiler #       option that results in lower performance and larger code size. TCPPSRC =  # List ASM source files here ASMSRC = $(PORTASM)  INCDIR = $(PORTINC) $(KERNINC) $(TESTINC) \          $(HALINC) $(PLATFORMINC) $(BOARDINC) \          $(GFXINC) \          $(CHIBIOS)/os/various/devices_lib/accel \          $(CHIBIOS)/os/various  # # Project, sources and paths ##############################################################################  ############################################################################## # Compiler settings #  MCU  = cortex-m4  #TRGT = arm-elf- TRGT = arm-none-eabi- CC   = $(TRGT)gcc CPPC = $(TRGT)g++ # Enable loading with g++ only if you need C++ runtime support. # NOTE: You can use C++ even without C++ support if you are careful. C++ #       runtime support makes code size explode. LD   = $(TRGT)gcc #LD   = $(TRGT)g++ CP   = $(TRGT)objcopy AS   = $(TRGT)gcc -x assembler-with-cpp OD   = $(TRGT)objdump SZ   = $(TRGT)size HEX  = $(CP) -O ihex BIN  = $(CP) -O binary  # ARM-specific options here AOPT =  # THUMB-specific options here TOPT = -mthumb -DTHUMB  # Define C warning options here CWARN = -Wall -Wextra -Wstrict-prototypes  # Define C++ warning options here CPPWARN = -Wall -Wextra  # # Compiler settings ##############################################################################  ############################################################################## # Start of default section #  # List all default C defines here, like -D_DEBUG=1 DDEFS =  # List all default ASM defines here, like -D_DEBUG=1 DADEFS =  # List all default directories to look for include files here DINCDIR =  # List the default directory to look for the libraries here DLIBDIR =  # List all default libraries here DLIBS =  # # End of default section ##############################################################################  ############################################################################## # Start of user section #  # List all user C define here, like -D_DEBUG=1 UDEFS =  # Define ASM defines here UADEFS =  # List all user directories here UINCDIR =  # List the user directory to look for the libraries here ULIBDIR =  # List all user libraries here ULIBS =  # # End of user defines ##############################################################################  RULESPATH = $(CHIBIOS)/os/ports/GCC/ARMCMx include $(RULESPATH)/rules.mk  What could be wrong? Microsd card is partitioned in FAT and there is also test.txt file on it which i would like to read. P.S i'm using Open407V-D development board(http://www.wvshare.com/product/Open407V-D-Standard.htm) which has a SDIO socket.