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[on:]

what is the meaning of those commands  in SerialTime example ?

Code:

#define TIME_MSG_LEN  11   // time sync to PC is HEADER followed by unix time_t as ten ascii digits
#define TIME_HEADER  'T'   // Header tag for serial time sync message
#define TIME_REQUEST  7    // ASCII bell character requests a time sync message
.....
time_t requestSync()
{
  Serial.print(TIME_REQUEST); 
 return 0; // the time will be sent later in response to serial mesg

Where can I read about those commands ?
 I google them  and  only the SerialTime example came up
I read  time  filefolder  and I can't find anithing about those commands (with capital letters like:TIME_MSG_LEN)

[Reply #1 on:]

Code:

#define SOMETEXT SOMETHINGELSE

will cause in the compiler to replace SOMETEXT with SOMETHINGELSE whenever it comes across it in your code.  This allows you to use meaningful names and also for you to be able to change the meaning of SOMETHING in one place rather than searching through you code.

Google #define

[Reply #2 on:]

Code:

#define TIME_REQUEST  7

Tells the preprocessor to look for TIME_REQUEST anywhere in the code and replace it with 7. So the line

Code:

Serial.print(TIME_REQUEST);

becomes

Code:

Serial.print(7);

before it is compiled. If you're asking for what those specific TIME_ values mean, then the comments right next to them should tell you.

[Reply #3 on:]

thank you for your answers . they were enlinghtening