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  • Serial.print(valor / 700.0f * 255); would work better. 700.0 is a double not a float and so by the rules of the c language that entire calculation is done as doubles. Adding that f in turns it into a float. On a low end microcontroller you really want to avoid doubles as much as possible, double operations are twice as slow as a floats and floats are slow enough already. Commented Dec 6, 2016 at 10:12
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    @Andrew: The OP is working on an Uno. A double is the same as a float on the AVRs. Commented Dec 6, 2016 at 10:41
  • That in this particular case the standards aren't followed and so it doesn't make a difference isn't a good justification for inefficient coding. Pressing 1 extra key is a small price for a good habit and portable efficient code. Commented Dec 6, 2016 at 10:49
  • Not meaning to nitpick but I'd just point out that mapping floats to doubles on the UNO is a software choice implemented in the gnu compilers, not hardware-driven at all as the hardware has no support for floating point. A different tool-set might well implement a different choice. So could a programmer using gnu for that matter, by defining an 'sfloat' (small- or single-precision float) object and its arithmetic operators. Commented Dec 6, 2016 at 21:13