Serial Port Complete - Latest Microcontroller projects

An RS-485 Network

switch (lower_nibble)

{

case '0': case '1': case '2': case '3': case '4':

case '5': case '6': case '7': case '8': case '9':

{

lower_nibble -= 48;

break;

}

case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':

{

lower_nibble -= 87;

break;

}

case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':

{

lower_nibble -= 55;

break;

}

default:

{

lower_nibble = -1;

break;

}

}

if ((upper_nibble > -1) && (lower_nibble > -1))

return_value = (upper_nibble << 4) + lower_nibble;

else

return_value = -1;

return return_value;

}

$ 
  8 

$

Firmware must decode received data to find out if it contains a supported com-

mand.