NTP Client tutorial code simplification

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1

Hello,

In the Ntp Client tutorial, the example code convert an UNIX time stamp to be sent as HH:MM:SS to Serial :

// print Unix time:
Serial.println(epoch);
// print the hour, minute and second:
Serial.print("The UTC time is ");       // UTC is the time at Greenwich Meridian (GMT)
Serial.print((epoch  % 86400L) / 3600); // print the hour (86400 equals secs per day)
Serial.print(':');
if (((epoch % 3600) / 60) < 10) {
    // In the first 10 minutes of each hour, we'll want a leading '0'
    Serial.print('0');
}
Serial.print((epoch  % 3600) / 60); // print the minute (3600 equals secs per minute)
Serial.print(':');
if ((epoch % 60) < 10) {
    // In the first 10 seconds of each minute, we'll want a leading '0'
    Serial.print('0');
}
Serial.println(epoch % 60); // print the second

It could be simplified by the use of sprintf() function :

byte h=0,m=0,s=0;
char heure[9];
// print Unix time:
Serial.println(epoch);
// print the hour, minute and second:
Serial.print("The UTC time is ");       // UTC is the time at Greenwich Meridian (GMT)
h = (epoch % 86400L) / 3600;
m = (epoch  % 3600) / 60;
s = epoch % 60;		
sprintf(heure,"%02d:%02d:%02d",h,m,s);
Serial.println(heure);

Regards

Pierre

2

Compiling the tutorial code for Uno:

Sketch uses 11436 bytes (35%) of program storage space. Maximum is 32256 bytes.
Global variables use 650 bytes (31%) of dynamic memory, leaving 1398 bytes for local variables. Maximum is 2048 bytes.

Compiling your code for Uno:

Sketch uses 12870 bytes (39%) of program storage space. Maximum is 32256 bytes.
Global variables use 666 bytes (32%) of dynamic memory, leaving 1382 bytes for local variables. Maximum is 2048 bytes.
3

Good to know. I missed this increase of memory needed. I suppose it's the binaries of sprintf().
By the way, If you want to use less Serial.print calls and no more memory, you could directly populate the string :

char heure[]="00:00:00";
byte h=0,m=0,s=0;
// print Unix time:
Serial.println(epoch);
// print the hour, minute and second:
Serial.print("The UTC time is ");       // UTC is the time at Greenwich Meridian (GMT)
h = (epoch % 86400L) / 3600;
m = (epoch  % 3600) / 60;
s = epoch % 60;		
heure[0]=h/10+48;
heure[1]=h%10+48;
heure[3]=m/10+48;
heure[4]=m%10+48;
heure[6]=s/10+48;
heure[7]=s%10+48;
Serial.println(heure);

The sketch uses now only 11326 bytes, but the source code is less clear.

4

but the source code is less clear.

It would be clearer with some spaces and with '0' instead of 48.