Hi to you all,I've a firmware running on a NXP LPCLink2 (LPC4370: 204 Mhz Cortex M4 MCU) board which basically does this:
My problem is that my code is too slow, and every now and then and overwrite occurs.
Using the DMA I'm saving the ADC data, which I get in Twos complement format (Offset binary is also available), in a uint32_t buffer and try to prepare them for the CMSIS DSP function by converting the buffer into float32_t: here's where the overwrite occurs. It's worth saying that I'm currently using Floating point Software, not hardware.
The CMSIS library also accepts fractional formats like q31_t, q15_t and so on, and since I don't strictly need floating point maths I could even use these formats if that could save me precious time.It feels like I'm missing something important about this step, that's no surprise since this is my first project on a complex MCU, any help/hint/advise would be highly appreciated and would help me in my thesis.
I'll leave here the link for the (more datailed) question I asked in the NXP forums, just in case: LPC4370: ADCHS, GPDMA and CMSIS DSP | NXP Community .
Thanks in advance!
Regarding the sign extension, there is a very simple way to do it : change the scale of your data !
Before Andrea posted what he is doing with the samples, this is not an advisable trick. Now that finding the minimum and maximum values seems the only task to be done, left-shift/change of scale is a simple but effective way of sign extension.
For this project, writing a custom function for searching the minimum and maximum values rather than using the CMSIS functions is more advantageous. This is because the input samples need to be sign-extended first and the search for minimum and maximum values can be combined in a single function.