It is an error in theoretical concepts that stopped us for a few hours. When printing a hexadecimal value on the screen, sending this by bluetooth and printing it on the screen of a cell phone, the ASCII characters vary but the hexadecimal code was maintained.

To understand this problem we started to investigate and we found that the ASCII code is divided into "printable characters" and "Extended alphabet". Next we explain each one:

Printable Characters:

It is a character code based on the Latin alphabet, as it is used in modern English. It was created in 1963 by the American Standards Committee as a recasting or evolution of the code sets then used in telegraphy. Later, in 1967, lowercase letters were included, and some control codes were redefined.

Currently it defines codes for 32 non-printable characters, of which most are control characters that have an effect on how the text is processed, plus another 95 printable characters that follow them in the numbering (starting with the space character).

The ASCII code uses 7 bits to represent the characters, although initially it used an additional bit (parity bit) that was used to detect errors in the transmission. It is often incorrectly called ASCII to several 8-bit character codes that extend the ASCII with characters from languages other than English, such as the ISO / IEC 8859-1 standard. This is just the error we found. The screen works with a Japanese ASCII while the cell phone works on a Mexican ASCII, theoretically, if the language of the cell is changed to Japanese, the same characters would be seen.

Extended ASCII:

As computer technology spread throughout the world, different standards were developed and companies developed many variations of the ASCII code to facilitate the writing of languages other than English that use Latin alphabets.

So, any 8-bit character set, in which the codes 32 to 126 (0x20 to 0x7E) match the printable ASCII characters, as well as the control codes from 8 to 13 but with characters from 127 onwards , they are called "Extended Alphabet"

The extended ASCII encodings also use part or all of the codes greater than 128 to encode additional characters to the printable ASCII characters.