I’m interested in the DSO nano - after reading the newly added manual, I saw that it supports a “FREQN” mode - does this mode mean, there is a FFT analyzer included? Or does it just show the “main frequency” of the signal?
Perhaps there is an opportunity for the open source community to add new features to the DSO nano?
kind regards
Michael
I afraid “FREQN” mode just means that it can measure the cyclely waveform’s frequency and show in the screen.
if your waveform is not cyclely it will make some error on show.
Thanks
FreeZinG
OK, thanks for checking!
BTW, I don’t know, how the DSO nano is programmed (I assume using C and not directly machine code?) and if it has a powerful enough CPU - but I did some FFT work in the original iPhone (the iPhone uses a 700 DMIPS cpu but the iPhone is under-clocked so it might not reach this performance, compared to the one in the DSO Nano Cortex M3, which is specd at 125 DMIPS @ 100MHz) - but I guess doing some offline FFT could still be possible.
I was using a very simple FFT package (sourceforge.net/projects/kissfft/ - BSD license) which is not even tuned for speed but could get very good performance out if it - of course here the FFT-windows are longer (at 1MHz sample rate compared to the 44.1kHz on the iPhone).
Doing a small comparison:
iPhone: Doing an FFT of a window of 4096 samples takes: 3ms
DSO nano: Samplerate is approx 20 times larger, and assuming the CPU is 5 times slower -> it takes approx. 100 times longer -> 300ms
This would still be very acceptable performance, as it means the FFT display would update 3 times a sec. And because the screen-size is small anyway, you probably don’t need that large FFT-windows and could reduce it (the calculations above are for an approx. 5Hz frequency resolution).
Hi,
If you read the DSO nano manual, you will see the microcontroler used in the DSO nano is the STM32F103VBT6 (based on ARM Cortex M3), this one can maximum be clocked at 72MHz (and can reach 90 DMIPS source: STM32 docs, but according to some forumers on a topic, we can´t reach this performance (?!) ). I don´t know the clock frequency used in the DSO nano but according to the reference manual, 1MSPS ADC´s rate can only be achieved with a 56MHz System Clock.
On the ST´s site you can find a DSP library which include an FFT function.
See user´s manual: st.com/stonline/products/lit … /14988.pdf
you can download the DSP library firmware here (in firmware section): st.com/mcu/familiesdocs-110.html
And you can find somes discussions about in the forum…
An other idea which can be interesting is to improve the ADC accuracy by oversampling (for lower frequency signals)… But it depends from other hardware accuracy too…
(I´ve just discovered the DSO nano today and I actually programm on STM32 but not with FFT calculations. I will probably buy one when it will be possible… Do you know when last release will be available?)
Regards,
Vince
PS: Modified Friday 23 Oct. at 10h (GMT+1)
if ues this hardware to do FFT , then as somebody said : the result cann’t be calculate for how many " frames per second ", but to say how many seconds per frame… 