Looking for a trig function library

[snehadakhare01]

Hello ST Community,

I'm working on an application using the STM32F103C8T6 microcontroller that implements a Sliding Mode Observer (SMO) and Park/Clarke transformations. I'm facing significant performance challenges due to the computational overhead of the floating-point trigonometric functions  atan2f.

My system requires a 50us loop execution time, but the SMO alone is taking approximately 20us, largely due to these trigonometric functions. I need to optimize this to meet my timing requirements.

Here's a breakdown of my current implementation:

• MCU: STM32F103C8T6
• Application: SMO and Park/Clarke transformations
• Problem: Excessive execution time of  and atan2f within a 50us loop.
• Current Performance: SMO takes ~20us.
• Compiler: stm32cubeide
• Optimization Flags: O2
• Clock Frequency: 20khz

Please tell me solution

[TDK]

Perhaps move to fixed point and use the precompiled DSP library.

https://github.com/ARM-software/CMSIS-DSP/tree/main/Source/FastMathFunctions

Floating point calculation on a chip without an FPU are going to be incredibly slow. Plenty of inexpensive chips out there with an FPU.

[Andrew Neil]

Lookup tables?

[Tesla DeLorean · Accepted solution]

Not the first to have these types of problems, perhaps consider Google, et al

https://gist.github.com/volkansalma/2972237

[snehadakhare01]

Sir please provide same for tanf , sinf, and cosf

Your solution is helpful for me, Thanks for reply and providing solution sir

[snehadakhare01]

Sir Thankyou so much Please can you provide me implementation for lookup table

[gregstm]

... and maybe add interpolation to that lookup table too. 

https://wirelesspi.com/3-ways-to-approximate-atan2-in-hardware/

[snehadakhare01]

Sir Please send me same for tanf