Using floats with sprintf, gcc-arm-none-eabi, nRF51822

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

RVA — Tue, 01 Aug 2023 10:43:44 GMT

Works also in nrf52840 with gcc-arm-none-eabi-6-2017-q2-update

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

lvh831 — Wed, 22 Feb 2023 19:18:26 GMT

Thank you Eliot. You're a kind person!

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

Aboisleux — Wed, 24 Jan 2018 13:45:27 GMT

thank you so much!!! I was stuck, and this was driving me crazy. I could do sprintf for integers

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

Luis — Fri, 23 Oct 2015 11:44:47 GMT

you saved me so much time. Thanks!

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

Mahesh Venkitachalam — Mon, 05 Oct 2015 06:18:58 GMT

great find!

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

Eliot Stock — Tue, 27 Jan 2015 21:21:43 GMT

Fine for my use case but useful to know, thanks.

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

Charles Manning — Tue, 27 Jan 2015 21:16:39 GMT

Just a side comment to what you're trying to do...

Floats only give about 7 digits of precision. That will give you a worst case precision of about 2 metres .

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

Pher — Tue, 27 Jan 2015 12:58:50 GMT

Hi Elliot, do you now if it is possible to do the same thing on KEIL MDK?? By now, i cant use printf functions with floats inside! Every time i try to use it, in the firsts prints i have always the result of 0.000000 and the program crashes a little bit after with an hard fault handler!

Regards

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

FormerMember — Mon, 17 Feb 2014 15:06:58 GMT

Strange. I don't have that flag. Well, its fine in any way as long as it works.

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

Eliot Stock — Mon, 17 Feb 2014 14:54:14 GMT

The trick seems to be to add this linker flag to your Makefile:

LDFLAGS += -u _printf_float

Looks like "printf" here also applies to sprintf.

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

Eliot Stock — Mon, 17 Feb 2014 14:52:57 GMT

Thanks! There was in fact a linker flag in the Makefile in that project which did the trick. Posting it below.

RE: Using floats with sprintf, gcc-arm-none-eabi, nRF51822

FormerMember — Mon, 17 Feb 2014 14:14:14 GMT

Hi Eliot, Printing floats is working for me with GNU GCC 4.8.3 in nrf51822. I am using printf as shown by a kind person here. For example


    int i = 7;
    float ab = 1.2;
    printf("A printf test: %.3f %d\n", ab, i);

gives an output of

A printf test: 1.200 7

Try this. As far as I know, I don't see anything special related to floats in my makefile. PS. Cool start-up. All the best! Prithvi