Floating point calcs on Kinetis CPU CW 10.1 MQX 3.7

intevac_coder — Wed, 22 Jun 2011 05:49:07 GMT

Hello,

I am having a little challenge getting some basic floating point calculations to work with the K40 tower system.

HW: K40 tower system

CW Dev studio 1.0.0 Build Id: b15_2105-A22-A1

CW ver 10.1.5, build id 110204

MQX 3.7

In the debugger, I am stepping through my code and find that the floating point calculations are not working correctly. Code like this:

float DG_const;

DG_const = 1023.0 / 21467.05;

DG_const reports back a value of 3.07e-44 in the variables window.

and the line

DG_denom = powf(255.0 , 1.8);

shows DG_denom = 0

in the variables window. I have #include <math.h> in the header. Is there a setting(s) that need to be added for f-p calculations to work?

Thanks!

Re: Floating point calcs on Kinetis CPU CW 10.1 MQX 3.7

intevac_coder — Thu, 23 Jun 2011 06:04:03 GMT

I received a message from Freescale support:

I think you should ewl model for your library configurations. You need choose c9x if you want to use math function like powf().see enclosed screenshot.

I extracted the description from help as below:

ewl and ewl_c++ models have a smaller memory footprint. Also, the ewl and ewl_c++ models have relevant sub-models that allow the user to select the desired print and scan formatters and the IO scheme.

c9x and c9x_c++ models are fully C99 compliant. The c9x and c9x_c++ models do not have sub-models.

The attached Setlib distills down to this:

Floating Point

To get floating point calcs to work, the Compiler tool settings must be changed.

Click on the project in the Project window.

Select Project from the menu:

Properties

Tool Settings->Librarian->Model->c9x

The EWL library has a smaller footprint but doesn’t support floating point calculations.

topic Floating point calcs on Kinetis CPU CW 10.1 MQX 3.7 in Kinetis Microcontrollers

Floating point calcs on Kinetis CPU CW 10.1 MQX 3.7

Re: Floating point calcs on Kinetis CPU CW 10.1 MQX 3.7