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LPC55S69 PowerQuad Example

Question asked by Charles Lonsdale on Mar 22, 2019
Latest reply on Mar 27, 2019 by Alexis Andalon


I'm using the PowerQuad for FFT512 functions, and am using the example in AN12282 as a basis, however I am having some problems using the libraries that are released under the SDK as follows.

1) I tried to access the FFT function using the CMSIS call arm_rfft_init_q15() and arm_rfft_q15() both of which are remapped to the relevant PowerQuad function using the code in fsl_powerquad_cmsis.c. However I need to include the header file from the CMSIS code "arm_math.h" to make the structure arm_rft_instance_q15 available. This results in a compiler error because there is no FPU/DSP accelerator present. To get round this I access the PowerQuad driver functions directly.

2) I then need to calculate the magnitude of the complex result of the FFT. In the example this is done using arm_q31_to_float and arm_cmplx_mag_f32. However, this is not mapped to a PowerQuad function, nor does there seem to be an equivalent function in the current PowerQuad drivers.


I've also looked at the PowerQuad driver examples in the SDK which have been very useful, but these fall short of the required magnitude calculation.


Are there complete source code files for the examples in AN12282 so I can see where my error is, and are these examples based on a currently unavailable version of PowerQuad drivers?


Does anyone have any other suggestions?


Kind Regards