Rounding Error in 'printf(): Non-Digit ASCII characters generated

[JoWi]

Hi Community,

printf()  (and variants) fail on rounding floats: This is is probably an error in the printf implementation. I tested it with SDK 16.0 on NRF52840.

Format String "%.1f" with argument "0.95" should print "1.0" (or at least "0.9"), but the rsult is "0.:".

It would be nice to have this working.

Best regards,
Jo

// Test function:
case 'z':
	{
	  float fval;
	  fval=atof(input+1);
	  printf("Fval: '%.1f'\n",fval);
	}
	break;

...
// OUTPUT:

>z0.9
Fval: '0.9'

>z0.94
Fval: '0.9'

>z0.95
Fval: '0.:'             <---- ??? Rounding Error (ASCII ':' follows '9')

>z0.96
Fval: '1.0'

>z1.2345
Fval: '1.2'

>z1.25
Fval: '1.2'

[Karl Ylvisaker]

Hi Jo,

What Turbo J is saying is correct - printf is implemented in the C standard, not in the SDK. The specific behavior of the printf function is dependent on what compiler you are using. If you want to read more about the logger module from the SDK you can do so here, and if you want to look the underlying macro code, it is located in the nrf_log.h file from the SDK log library.

Best regards,
Karl