PICAXE Microcontroller/Personal Web Server
PC Communicates with the PICAXE and the INTERNET
Gathers Data, Controls Stuff
Read first: Communicate with the PICAXE
Background
This website, maxmcarter.com, is hosted on a server running on an old desktop PC here in my home shop/lab. It's possible to do that because my ISP provides a static IP address. The server is Apache 2, with PHP5 and (Active)Perl installed, running over Windows XP.
Among the advantages of hosting a website on your own PC is cost savings. The only ongoing cost is for electric power - about $6 per month in this case. The server runs 24/7/365. The cost of my connection to the internet is not included since I would be paying for that anyway, even if there were no server. My ISP does not charge extra for the static IP and server connection.
An even bigger advantage to having the server on the premises is that it gives me total control of the physical server and the website. I can do pretty much anything I want with the thing. Among my interests is gathering realtime data from various experiments and making them available on the internet via the webserver. Here's an earlier example. The PICAXE microcontroller - possibly the easiest-to-use microcontroller ever - offers another, simpler approach to data gathering and control via PC/web server.
Server/PICAXE Interface
This page shows some coding that will interface a PC/server to the PICAXE via the serial port. Before reading, please read Communicate with the PICAXE for information on physically connecting, interfacing and communicating with the PICAXE chip. The applications shown here are extensions of the get-data-control-stuff-with-a-PC-via-the-serial-port idea introduced in that article. These examples in no way exhaust the possibilities for remote control and monitoring afforded by mating the PICAXE to a server. More pins on larger PICAXE chips; more chips connected together in a wired or wireless network; there are endless possibilities.
This page will not show how to set up a web server. If you're interested in doing that, I found Apache, MySQL, and PHP Web Development All-in-One Desk Reference for Dummies to be helpful. There are many other how-to references out there, along with LOTS of information available on the Web.
If your PC is not a web server (and you don't want it to be), Perl and the CGI script can be run on your PC and addressed directly from your browser. (A GUI written in C# or Visual Basic would be a another approach. See Virtual Serial Port Cookbook, for example.)
The Code
With the server hardware and software background in place, implementation of the PICAXE/server interface involves four areas:
- Verifying Apache configuration,
- Installing the serial port driver,
- Copying the CGI script file to the cgi-bin folder, and
- Loading the PICAXE Basic program.
Open your Apache configuration file and make sure the statements
ScriptAlias /cgi-bin/ "path/cgi-bin/"and
<Directory "path/cgi-bin">
AllowOverride None
Options None
Order allow,deny
Allow from all
</Directory>
are present and uncommented (uncomment if it's commented). Edit "path" to show the path to the cgi-bin folder on your machine (for example: c:/program files/apache group/apache2). Save and re-start Apache. Note: It is only necessary to do this once.
The serial port driver:
The serial port driver is a perl module called "Win32-SerialPort". The module is installed from the command line in the perl/bin directory as follows:
From the Windows start menu click run, in the Open: field type CMD, click OK, navigate to the perl/bin directory.
Type ppm<return>.
Then type install http://www.bribes.org/perl/ppm/Win32-SerialPort.ppd<return>.
The program will find and install the module. Also, "Win32-API" must be installed if it isn't already :
Type install http://www.bribes.org/perl/ppm/Win32-API.ppd<return>
Note: It is only necessary to do this once.
The CGI script (for the Control Page application above):
This script supports only the Control Page application above. Scripts for other applications should be placed in the cgi-bin folder and called by those applications. (Additional scripts can be seen here.) Copy the following Perl code (or other script) to your favorite editor (eg Notepad), add paths, filenames, URLs, etc. where called for, and save to the cgi-bin folder as a Perl file (filename.pl):
#!path/bin/perl.exe
# the very first line tells Apache where Perl is,
# the line must start with "#!" path usually is c:/perl
print "Content-type: text/html\n\n"; #generates HTML page
print "<html>\n
<head>\n
<title>Web Server/PICAXE Control Interface Page</title>\n
</head><body>\n
<table width='100%' border='0'><tr><td><td width='80%'>\n
<h1 align='center'>PICAXE Control Page</h1>\n
<hr align='center'>\n
<h3>Control 1</h3>\n
<h4>08M Out 2 (pin 5)</h4>
<p>Select command, click SEND</p>
<form method='post' action='/cgi-bin/filename.pl'>\n
<input type='radio' name='c' value='n'>TURN DEVICE 1 ON<br>\n
<input type='radio' name='c' value='f'>TURN DEVICE 1 OFF<br>\n
<input type='radio' name='c' value='s' checked='checked'>GET STATUS<br>\n
<input type='submit' Value='SEND'>\n
</form>\n
<br>\n
<font size='4'>Control 1: </font>";
$cmd = readline(STDIN); #reads the input command from client browser
#$cmd will be "c=n" (on), "c=f" (off), "c=t" (temp) or "c=s" (status)
#open serial port
use Win32::SerialPort;
$Sport = new Win32::SerialPort('COM1'); #this creates an "object",
#"class" or something, named $Sport
$Sport->baudrate(2400); #configures serial port
$Sport->parity('none');
$Sport->databits(8);
$Sport->stopbits(1);
$Sport->handshake('none');
$Sport->write_settings;
$stoptime = time + 2; #gets computer time (seconds), adds 2 sec
#this is the length of time the program is allowed to run
sub get_control($) { #subroutine "get_control"
$Sport->write($cmd); #writes $cmd to serial port (sends command to picaxe)
$_ = ''; #clears $_ (sets to 'nothing')
do {
sub no_resp { #No response subroutine
print "<font size='4'>";
print "No response from sensor..."; #prints this and stops program
print "<br><br><hr>\n
</td><td></td></tr></table>\n
<p align='center'>Web host: <a href='URL'</a>yoursitename</p>\n
<div align='center'><img src='yourfavicon'></div>\n
</body>
</html>";
die;
}
if (time >= $stoptime) { #if current time greater than
#or equal to stoptime,
no_resp; #calls no_resp subroutine above
}
$_ .= $Sport->read(1); #reads serial port data, one chr at a time
#".=" is concatenate operator,
#concatenates new chr with previous chrs in the string
}
while (!/\r/); #until carriage return (\r) received
return $_; #ends do-while loop, returns $_ value
}
$_ = get_control (""); #calls the get_control subroutine above
@accum = split(' ',$_); #converts string to array, splits $_ at ' ' (space)
if ($accum[0] == 0) {
print "<font size='5' color='red'>OFF</font>"; #prints "off" if first number in array = 0
}
elsif ($accum[0] == 1) {
print "<font size='5' color=' green'>ON</font>"; #prints "on" if first number in array = 1
}
$temp = $accum[1]; #this gets the 0-255 AD voltage reading from temp sensor
$temp = ($temp * 5.08); #This is the voltage scale factor; converts 0-1023 to tens of millivolts.
#The scale factor is determined by multiplying the power supply
#voltage (as measured with a digital multimeter) on the PICAXE chip by
#1000/1024. The power supply voltage in this case measured 5.2 volts.
#Thus, 5.2 x 1000/1024 = 5.08. If you don't have a digital multimeter,
#use 5.0 in the calculation; the scale factor in that case is 4.88
$temp = int($temp + .5); #rounds to nearest whole number
$temp = ($temp / 10); #converts tens of millivolts to degrees
$cal = 0; #calibration factor; change to positive or negative
#number to correct the sensor, if necessary
$temp = ($temp + $cal); #calibrates temperature sensor
print "<br><br><font size = '4'>Server room<br>temperature:
</font><font size='5' color='blue'>";
print $temp;
print "°C</font>";
print "<br><br><hr>\n
</td><td></td></tr></table>\n
<p align='center'>Web host: <a href='URL'>yoursitename</a></p>\n
<div align='center'><img src='yourfavicon'></div>\n
</body>
</html>";
The PICAXE code (supports all 3 applications above):
This code, in PICAXE Basic, supports polling from the control page, "get temperature" page, and graph generator applications above. Copy the code into the PICAXE Programming Editor and program the chip:
main:
SerIn 3, N2400, ("c="), b0 'gets first character after qualifier ("c=") from server
if b0 = "n" then 'looks for "on"
high 2 'turns on the output (start motor, turn on light, etc.)
gosub get_status 'calls up "get_status" subroutine below
else if b0 = "f" then 'looks for "f" (off)
low 2 'turns off the output
gosub get_status 'calls up "get_status" subroutine below
else if b0 = "t" then 'looks for "t" (temp)
gosub get_temp 'calls up "get_temp" subroutine below
SerOut 0, N2400 , (#b2, 13) 'sends temp + CR to server
else if b0 = "s" then 'looks for "s" (status)
gosub get_status 'calls up "get_status" subroutine below
endif
goto main
get_status:
readoutputs b1
gosub get_temp 'calls temp subroutine below
SerOut 0, N2400, (#bit10 ,32, #b2, 13) 'Sends status and temp to server.
'Bit 10 is the on/off status of Out 2.
'The bit is transmitted as an ASCII
'character - ie,
'0 = ASCII 48, 1 = ASCII 49.
'32 is space, #b2 is the temp data,
'13 is CR (carriage return)
return
get_temp:
ReadADC10 4, b2 'Reads the voltage on In 4; returns a value between 0 and 255,
'ie, the least significant 8 bits (byte) of a 10-bit word.
'This byte represents a voltage of 0 to approximately 1.25.
'It's not necessary to read the most significant bits.
'The server calculates the actual voltage and temperature
'from this data.
return
"These examples in no way exhaust the possibilities for remote control and monitoring afforded by mating the PICAXE to a server."
