On Tue, Jul 11, 2017 at 8:17 PM, William Hermans <[email protected]> wrote:

> SPI is notoriously finicky when it comes to high speed, and noise. Since
> I'm not an EE, I could not say much more than that. Typically though, from
> what I understand, traces can not be very long.
>

Additionally, this could very well be a Nodejs bottleneck. I've personally
experienced first hand how slow Nodejs really is when working with fast
moving code. I notice the title "shiftout.js" but you're also talking about
C too. So maybe you're using a hybrid of the two ? A bit confusing, but
maybe some clarity on the subject is deserved ?

Using my own  javascript library, which pretty much just encapsulates the
sysfs file entries. When toggling GPIO, I've noticed it peters off at about
1Khz, or slightly less. That's just using a simple XOR binary operation.
Arguably, using /dev/mem/ and mmap() would be faster, but the speed of
scripting language code is alway going ot be a bottle neck. First, because
it's an interpreted language, and second, because the "binary" size is huge
compared to something like C. It's going ot be a lot slower.

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