Web controlled robot

One way you can command your robot is via CGI invoking a C program
that sends commands over the serial port to the PIC.

If you want live data to be displayed on the web page, use AJAX.  I
haven't used it personally, but a buddy of mine did, and the results
are impressive.

BRW

I mocked up a simple robot control and status display in ajax earlier
this year.  (For a robot that I subsequently abandoned for unrelated
reasons.)  Ajax is definitely what you want to go with for real-time
systems like robots.  I would recommend *against* touching the serial
port directly from a CGI script, however.  There are a few reasons for
this: (1) you can get several web requests at a time, and contention
will lead to unpredictable results (2) if you're reading data from the
pic, your CGI will have to open the port and wait for whatever data
you want to display to come it.  The way I did it was to have a simple
perl daemon (you could do it in c with a few more lines of code) open
all the serial ports (the robot had a few of them) and record the
incoming data.  It would also open a local tcp socket.  CGI scripts
would connect to that and query for particular items of data (which
the daemon cached so were available instantly) and issue commands
(which the daemon could apply arbitrary command policies to.)  You
could also write a controller program that uses the same API as the
CGI scripts.  That way changing the high-level control does not
require restarting the low-level input/output systems.

-chris.

This looks like it could be the answer.  Had a quick look on wiki and
it sounds right, so on with a tutorial.  If I get anything going I'll
post a ulr to play with :)

If not I might be back for more advice. ;)

A common approach to this problem is to write a daemon, a back-ground
program, that talks to the serial port and device, and offers a protocol
to UI programs such as a web server.

This was the approach we took in our book "Linux Appliance Design".  We
had five types of UIs : web/AJAX, command line, framebuffer and LIRC,
SNMP, and a hardware based front panel.  We used the RTA library on our
daemon (a simple alarm system) to give the common protocol used by all
of the UIs.

hope this helps
Bob Smith

Thanks all.

I have started playing with deamons in C. I've got my program to fork
off to make it a deamon. Im gonna use a fifo pipe (probably on a ram
disk so I don't over use the flash disk) and then get the data via
Ajax onto the web page.

Ajax<---->pipe<---->deamon<---->robot

The deamon will handle all the serious bot code such as mapping / path
planning etc.

I havn't got the fifo pipe working yet. Thats the next step. Then on
to ajax to see if I can get some live data up.

Cheers for the pointers

What this space..........

:-)

Rob