Hi All,
In my GCC program:
fprintf_P(stdout,PSTR("Foo=%f\n"),5.0);
produces:
Foo=?
while:
fprintf_P(stdout,PSTR("Foo=%d\n"),5);
produces:
Foo=5
I am linking in:
libprintf_flt.a
libscanf_flt.a
Any idea why the float isn't recognized?
Problems printing floats
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Message
I would guess that you are not actually linking the libprintf_flt.a
Copy and paste the Studio Build Window for a complete compilation. ( Make clean first )
David.
Make sure your makefile PRINTF_LIB value referst to the right library:
#Additional libraries. # Minimalistic printf version PRINTF_LIB_MIN = -Wl,-u,vfprintf -lprintf_min # Floating point printf version (requires MATH_LIB = -lm below) PRINTF_LIB_FLOAT = -Wl,-u,vfprintf -lprintf_flt PRINTF_LIB = $(PRINTF_LIB_FLOAT) # Minimalistic scanf version SCANF_LIB_MIN = -Wl,-u,vfscanf -lscanf_min # Floating point + %[ scanf version (requires MATH_LIB = -lm below) SCANF_LIB_FLOAT = -Wl,-u,vfscanf -lscanf_flt
avr-gcc.exe -mmcu=atmega168 -Wl,-Map=CushionController.map CushionController.o uart.o -lprintf_flt -lscanf_flt -o CushionController.elf
So, the correct libraries are linked in. The resulting elf file is about the size you'd expect with both of those libraries linked in.
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Joined: Mon. Jul 18, 2005
Posts: 101163 View posts
Location: (using avr-gcc in) Finchingfield, Essex, England
If you use Mfile this would have been MUCH easier but the point is there are TWO things you must do to enable printf_flt support. The -l you show above is one half of the jigsaw the other, as show in an Mfile generated Makefile such as the one fizgig posted above is the need for:
-Wl,-u,vfprintf
So I guess your linker invocation should be:
avr-gcc.exe -mmcu=atmega168 -Wl,-Map=CushionController.map -Wl,-u,vfprintf CushionController.o uart.o -lprintf_flt -lscanf_flt -o CushionController.elf
But do yourself a favour and check out Mfile!
Oh and if you are using scanf as well you need the equivalent linker command for it too as shown in fizgig's post above.
