So there was this web page, nothing more than a text file in fact, which I was compelled to check regularly. I had ordered something online from a company whose web-store design was still in the dark ages, and their “method” of letting customers know whether or not their products had shipped was to periodically update a web-viewable text file with a public list of all the order numbers that had recently shipped. Very private and secure, I know.

No, no, they couldn’t possibly email this information to you — you had to check the page manually. And if your products were backordered, as mine were, you’d be checking often.

Well, that’s just stupid, I thought, and since I had a computer sitting right in front of me, I thought it might be a good idea to automate the process.

So I cobbled together a little Python script on my Ubuntu box, which uses the pycURL interface to grab the URL in question, parse it, search it for my order number, and then fire me off an email (using sendmail) if and when it finds anything.

I automated the script to run hourly using cron, like so:

crontab -e

and then included the following line in my crontab file:

# m h  dom mon dow   command
7 * * * * /path/to/searchagent.py

Seven minutes after the hour (for luck), every hour, every day.

On the hunch that this script might be useful to somebody else, I decided to post it here. Fair warning to all: this is a huge hack, and I’m sure it needs work. Also, there’s probably a better method that I’ve completely overlooked. Comments, corrections, and suggestions are welcome, as always.

Here’s the script:

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Although the Arduino platform is ideal for standalone applications, it really comes to life when interfaced with a PC. Connect Arduino to a personal computer and you instantly add a ton of versatility and processing power to your project.

This tutorial will describe how to use Arduino to control a bank of four independent RC servos with your PC (or Mac, or *nix Box), using a USB cable and a modular Arduino-Python software stack.

The following discussion builds upon concepts presented in two previous articles, “Arduino Serial Servo Control” and “Joystick Control of a Servo.” As always, comments, critiques, or suggestions for improving or adapting this code are welcome and appreciated.

Project Outline

The primary goal for this project was to create a software stack that allows simple and flexible control of multiple servos from any type of Python script.

The solution has two basic components: (1) an Arduino sketch that waits for serial input from a connected PC, then moves each servo to its commanded position, and; (2) a Python module on the PC that opens the serial connection and formats the data packets expected by the Arduino.

Any other Python program written to sit on top of these two layers need not worry about the messy details of serial communication, but rather can just say something like, “Move servo #2 to 90 degrees.” Or, more precisely:

servo.move(2,90)

Easy, right? Let’s get started.

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Inspired by Armadillo Aerospace and their laptop-controlled Pixel rocket, I decided to figure out how to use an Arduino module to achieve wireless remote control of a flight vehicle.

Along the path to development, an achievable intermediate goal would be something like a wireless RC rover with a video camera, monitored and controlled with a laptop and joystick on a WiFi network.

Step one in the process is simple joystick control of a servo over a USB connection. This project builds upon the process documented in “Arduino Serial Servo Control.” I welcome any comments or suggestions for improving or adapting this code.

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