arduino format specifiers
* %d = signed integer %f = floating point number
* %s = string %.1f = float to 1 decimal place
* %c = character %.3f = float to 3 decimal places
* %e = scientific notation %g = shortest representation of %e or %f
* %u = unsigned integer %o = unsigned octal
* %x = unsigned hex (lowercase) %X = unsigned hex (uppercase)
* %hd = short int %ld = long int
* %lld = long long int