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A comment on How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers. Parent comment

Re:How We Turned 8 Popular STM32 Boards into Powerful Logic ... by patrickg_zill on Thursday March 23, 2017 @03:02PM (#13943037)
If you ran a different OS on the Pi, would you get the consistency? For instance, FreeRTOS has been ported (unsure of quality) https://github.com/jameswalmsley/RaspberryPi-FreeRTOS .
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Re:How We Turned 8 Popular STM32 Boards into Powerful Logic ... by dragontamer on Thursday March 23, 2017 @03:15PM (#13943162)
You'd get more consistency for sure, but nothing that approaches the 75MHz (13 nanoseconds!!) needed to capture data from the GPIO pins.

From my understanding of the Raspberry Pi, the GPIO pins simply weren't designed for that level of speed. Which is fine, the Raspberry Pi was designed for other stuff. Its all about tradeoffs.

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Re:How We Turned 8 Popular STM32 Boards into Powerful Logic ... by snovv_crash on Thursday March 23, 2017 @05:33PM (#13944554)
Maybe not capture, but you can write to the pins at least that quickly. I've seen projects that use the gpio of a raspberry pi to drive an FM transmitter at 100MHz.
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Re:How We Turned 8 Popular STM32 Boards into Powerful Logic ... by megous on Friday March 24, 2017 @01:11AM (#13946775)
The project you're thinking about uses internal PLL in the SoC. This has nothing to do with GPIO reading/writing.

http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspb...

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Re:How We Turned 8 Popular STM32 Boards into Powerful Logic ... by snovv_crash on Friday March 24, 2017 @04:36AM (#13947501)
Ah, my bad. I was actually thinking afterwards about how they could be doing the frequency shifts and what kind of sampling speed they would need for accurate, small frequency shift adjustments.
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