floating point in cortex m0, always reset.

hi,I write an algorithm running in cortex M0. It has some floating point multiplication.But the program always resets when encounter a floating point multiplication.And the code showed below:

    for (k = 0; k < 4; k++) { tmpx =   dbuffer[0] * a[k + 1]; dbuffer[k + 1] = dbuffer[k + 1] - tmpx; }  


dbuffer[] and a[] are float array. tmpx is a float variable. When I debug the program, the M0 resets at line "tmpx = dbuffer[0] * a[k + 1];" .And the value of dbuffer[0] is 1429983,a[k+1] is 0.00974910986.
I have tested this multiplication in a new project.And the code goes well and result is right.The test code is like below:

            float a = 1429983; float b = 0.00974910986; float c; c = a* b;  


So, I know M0 use softVFP. I have seen asm code such as __aeabi_fmul corresponding to my code.
Could anybody tell me what's wrong with my code?
Thank you very much.

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  • Hi and welcome to the community!

    I assume you use GCC, because of the '__aeabi_fmul' ... but it's still hard to guess what's wrong.

    Because the second attempt works, I believe the difference might be in the way the code is built.

    I will suggest that you create a new test-project, then first put your test-code in there, run it and see if it works.

    If the first test works, then change the new test-project to use the code with the for-loop.

    If it works now, without reseting, then I think you need to find the difference in how the code is built.

    ...Assuming you get it all working, you might want to consider changing for(k = 0; k < 4; k++) to for(k = 1; k < 5; k++) and then remove the '+1' from the index.

    It won't really do much difference unless you've turned off optimization, but it will make your code shorter and easier to read.

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  • Hi and welcome to the community!

    I assume you use GCC, because of the '__aeabi_fmul' ... but it's still hard to guess what's wrong.

    Because the second attempt works, I believe the difference might be in the way the code is built.

    I will suggest that you create a new test-project, then first put your test-code in there, run it and see if it works.

    If the first test works, then change the new test-project to use the code with the for-loop.

    If it works now, without reseting, then I think you need to find the difference in how the code is built.

    ...Assuming you get it all working, you might want to consider changing for(k = 0; k < 4; k++) to for(k = 1; k < 5; k++) and then remove the '+1' from the index.

    It won't really do much difference unless you've turned off optimization, but it will make your code shorter and easier to read.

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