STM32 convert an unsigned short array to a float array

Question

I have been doing research in google, however I cannot find a solution.

How to convert an unsigned short array to a float array in STM32? I need to perform multiplication between an unsigned short array with a float array. To use FPU and DSP library for STM32F4, the unsigned array is to be converted to floating point first.

There are only libraries converting signed short arrays to float arrays. How to convert an unsigned short array to a float array?

I doubt that you have this option. The DSP library provides operations on q15_t, which is the "fractional" version of int16_t. But as you mentioned, this is a signed short. I think that you can find the entire API in file arm_math.h (also on GitHub, at github.com/mikeferguson/stm32/blob/master/libraries/CMSIS/…). I believe that anything which is not in this file is simply not supported. — barak manos
– barak manos, Commented Jun 10, 2014 at 14:37
Thanks for your comment, @barakmanos . But it has to be done... The data in unsigned short are read from sensors therefore unsigned arrays have to be used to store them.. — richieqianle
– richieqianle, Commented Jun 11, 2014 at 3:31
So you'll have to create an array of 32-bit float elements, and copy each unsigned short element into it. — barak manos
– barak manos, Commented Jun 11, 2014 at 3:57
How to do that? One by one using my own function? Or there are built-in DSP instructions? There are DSP functions converting signed short array to float array btw. — richieqianle
– richieqianle, Commented Jun 11, 2014 at 4:02

unwind · Accepted Answer · 2014-06-10 14:35:45Z

1

By just storing them as float, I'd say:

void uint16_to_float(float *out, const unsigned short *in, size_t num)
{
  for(; num > 0; --num)
    *out++ = *in++;
}

It's up to the compiler to figure out what instruction(s) are best suited for this, but it's a pretty standard operation.

answered Jun 10, 2014 at 14:35

unwind

402k64 gold badges492 silver badges620 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

barak manos Over a year ago

I think that OP is looking for a way to pass this array to a "built-in" function (provided within the DSP library), which can regard this array of unsigned short values as an array of "fractional" values. In other words, I think that OP wishes to avoid taking an array of 16-bit integers as input and generating an array of 32-bit floats as output.

richieqianle Over a year ago

In the DSP library, the conversion has been done in this way: *pDst++ = ((float32_t) * pIn++ / 32768.0f);

richieqianle Over a year ago

One cent comment: Loop-unrolling could be used to optimize the code! stackoverflow.com/questions/2349211/…

Collectives™ on Stack Overflow

STM32 convert an unsigned short array to a float array

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related