[ale] Coursera: Arduino and C

[Charles Shapiro]

Oh, sorry, you right of course.

I'm controlling the LED through a CGI script ( or with a server written
with CherryPy).  My real limitation is that I'm only inputting whole second
values through the web page -- which is easily fixable at the cost of more
complex code.  I'm not going there for a demo.

What I was trying to say was that Raspbian is multi-user, hence a little
bit non-deterministic when it comes to really precise timing out the GPIO
pins.  If you *** must must must *** have a precise schedule, you probably
want ROS or some other RTOS, rather than a time-sharing one.

-- CHS

On Thu, Apr 5, 2018 at 2:18 AM, Joe Knapka via Ale <ale at ale.org> wrote:

> On Fri, Mar 23, 2018 at 10:20 AM, Charles Shapiro via Ale <ale at ale.org>
> wrote:
>
>> Byron is correct.   I'm currently working on an "Intro to Raspberry Pi"
>> class for Decatur Makers.  I've got code to control an LED from a browser
>> in several different ways.  It's pretty hard to get the LED to blink faster
>> than about once a second on a Pi running Raspbian because you're talking to
>> it through an entire multi-user OS.
>>
>
>
> I find that statement... shocking, I guess. There's an OS, yes, but also
> the RPi is clocked 100-ish times faster than an Uno. I mean it can render
> full-motion video in real time, right? C code to twiddle a pin on the RPi
> ought to be able to flash an LED at a rate that looks like steady-on to a
> human... your web page can invoke that C code as a CGI script or whatever.
>
> Or when you say "control an LED from a browser", do you mean the on/off
> transitions are being controlled by code running in the browser? Because
> then that would make sense to me. But it wouldn't be about Arduino vs RPi,
> it would be about browser+network vs hardware.
>
> Confused,
>
> - JK
>
> [snip]
>
>
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