On 7/7/15 9:59 PM, Brian Inglis wrote:
On 2015-07-04 07:13, Jim Lux wrote:
I've got a project I'm working on to make a sophisticated sundial with
moving mirrors. I've got a batch of Arduinos that move the mirrors to
the appropriate places, given the current sun angle, etc.
I've got a beaglebone that runs some python code to calculate sun
angle based on time
The beaglebone will have a GPS feeding it to get time.
BUT now, I'd like to add a web interface, so that it can be
manipulated by a mobile device using a browser.
One way I can think of is to run some sort of limited web server.
there are a couple that come with the beaglebone, including the python
"simplehttpserver".
But I'm sort of stuck on the interface between the webserver and the
other code running.
I've done this kind of thing where the one task goes out and updates
files in the tree that's being served by the web server, and that
works fine for "status display" kinds of things that don't update very
quickly. It's also nicely partitioned.
but I want to be able to change the behavior of the system (e.g. by
having the server respond to a PUT or something)
Is the best scheme to go in and modify the webserver code to look for
specific URLs requested, and then fire off some custom code to do what
I want?
May want to start with a control web page with an HTML FORM element and
embedded input elements - easy even if you have not done much form
design and entry implementation.
Submit target can be any URL designating a Python CGI script, which
generates at least a Content-type header and HTML on stdout returned to
the browser.
HTML output normally includes a copy of the original FORM (with values
passed selected for editing) as well as HTML output and maybe inline or
linked graphics.
You only need a web server that supports the CGI interface, with some
way to configure it and say where the scripts are.
See Python cgi, html, http module docs to DIY.
Yes, that seems to be the way..
The interesting thing is that the cgi needs to return reasonably fast,
or the user client will timeout, so it's not a good way to do something
that takes a long time. Great for "put parameters in a file" or "send
short command out IO device", not so great for "start long running
process that needs to continue after user has gone on to do other things.
So it comes down to lashing up some sort of interprocess communication,
whether it's a named pipe, a file that is shared between two processes,
IP sockets, etc.
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