i use an uno serial.print "?",meantime ,I want to serial.print gcode like "G91X10",but it will be mess up,what should i do ?any help will be appreciated.
what should i do ?
Write your code correctly.
If you need help, post the code you have, and the serial input it gets and the serial output it produces.
I suspect that you are using sprintf() with the %f format specifier, which is not supported. dtostrf() is the function to use.