Formatting strings for UART transmission

[faskr]

I am trying to write a program that sends position and battery data from TOC over UART. Some of the values are floats, so I am using sprintf with the specifier %f to format a string that includes these values. However, when I build I get this error:

/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-sbrkr.o): in function _sbrk_r': /build/newlib-pB30de/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/sbrkr.c:51: undefined reference to _sbrk'
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-writer.o): in function _write_r': /build/newlib-pB30de/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/writer.c:49: undefined reference to _write'
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-closer.o): in function _close_r': /build/newlib-pB30de/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/closer.c:47: undefined reference to _close'
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-fstatr.o): in function _fstat_r': /build/newlib-pB30de/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/fstatr.c:55: undefined reference to _fstat'
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-isattyr.o): in function _isatty_r': /build/newlib-pB30de/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/isattyr.c:52: undefined reference to _isatty'
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-lseekr.o): in function _lseek_r': /build/newlib-pB30de/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/lseekr.c:49: undefined reference to _lseek'
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: /usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libc.a(lib_a-readr.o): in function _read_r': /build/newlib-pB30de/newlib-3.3.0/build/arm-none-eabi/thumb/v7e-m+fp/hard/newlib/libc/reent/../../../../../../../../newlib/libc/reent/readr.c:49: undefined reference to _read'
collect2: error: ld returned 1 exit status

Is there a way to make sprintf work? Or is there an alternative way to format strings how I need?

[krichardsson]

spritnf() is not supported in the firmware, but perhaps you can use eprintf() instead?

You can also check out how the DEBUG_PRINT macro is defined when logging to UART

[faskr]

Thanks, eprintf seems to be just what I need. Is there also a way to read strings into floats, e.g. an equivalent for atof or sscanf?

[krichardsson]

Unfortunately not. as far as I know