In Creator 3.1, it introduces a new option. (See Pic)
This option has some problem at current version(220.127.116.110), user should use '-u _printf_float' command in Linker Command Line as a replacement.
In addition, due to sprintf function needs a big heap size, user may get a wrong result with default heap size(0x80). user should increase the heap size at .cydwr > system > Heap Size(byte). It will be enough to change to 0x200.
Thanks for this solution. I lost time for this bug.
It's clear and works like a charm