topic Re: Double data types in LPC Microcontrollers

Double data types

Bay — Wed, 06 Sep 2023 07:23:15 GMT

How to display the float number with 9 decimal places. example: 0.123456789

I have tried with below code, but the terminal displays The number is lf.

double number1=0.123456789;

PRINTF("The number is %lf", number1);

Re: Double data types

Alice_Yang — Wed, 06 Sep 2023 08:59:27 GMT

Hello @Bay

How about PRINTF("The number is %.9f", number1);.

https://community.nxp.com/t5/LPC-Microcontrollers/LPC54628-Printf-Floating-numbers-doesnt-have-minus-sign/m-p/1241343/highlight/false?lightbox-message-images-1242104=139054iDE12AB63C23CB9A3#M44168

Alice

Re: Double data types

frank_m — Wed, 06 Sep 2023 09:16:52 GMT

As Alice_Yang suggested, just specifiy the precision in the format string.
If you don't, the default value (usually 6 digits) is used.

> Double data types

> How to display the float number with 9 decimal places. example: ...

I hope you realized that "double" and "float" are different types of different size.
Only "float" is natively supported by Cortex M FPUs, and several clib implementations (i.e. printf()/scanf()) have no or limited support for "double" either.
Check the respective library documentation.

Re: Double data types

Bay — Wed, 06 Sep 2023 09:17:00 GMT

Hi Alice,
Thanks. It works.
How about if the user enters unknown number of decimal places?
How should write in this code line?
SCANF("%f ",&number1);
Why is the double data type not using %lf?