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