Half-Byte » netbook http://half-byte.com Doing more with less. Mon, 08 Mar 2010 19:46:22 +0000 en hourly 1 Using an USB External IDE HD Enclosure with an Internal DVD+RW http://half-byte.com/2010/02/02/using-an-usb-external-ide-hd-enclosure-with-an-internal-dvdrw/ http://half-byte.com/2010/02/02/using-an-usb-external-ide-hd-enclosure-with-an-internal-dvdrw/#comments Wed, 03 Feb 2010 00:35:38 +0000 nibble http://half-byte.com/?p=64 I’m super glad I ran across this post before shelling out the money to buy and external DVD+R/RW for my netbooks.  I pulled a Homer S. and asked myself why I didn’t think of this before…

]]> I’m super glad I ran across this post before shelling out the money to buy and external DVD+R/RW for my netbooks.  I pulled a Homer S. and asked myself why I didn’t think of this before…

]]> http://half-byte.com/2010/02/02/using-an-usb-external-ide-hd-enclosure-with-an-internal-dvdrw/feed/ 0 Servo Controller Driven over a USB-Serial Adapter http://half-byte.com/2009/09/20/servo-controller-driven-over-a-usb-serial-adapter/ http://half-byte.com/2009/09/20/servo-controller-driven-over-a-usb-serial-adapter/#comments Mon, 21 Sep 2009 07:26:02 +0000 nibble http://www.half-byte.com/2009/09/20/servo-controller-driven-over-a-usb-serial-adapter/ I recently thought up a great project idea that involved controlling motors from a PC.  I’ve done some experimenting with an Atmel USB interface in the past, but stopped when I hit a bug in the open source toolchain.  It was frustrating spending hours debugging only to find out the compiler wasn’t handing an instruction [...]]]> I recently thought up a great project idea that involved controlling motors from a PC.  I’ve done some experimenting with an Atmel USB interface in the past, but stopped when I hit a bug in the open source toolchain.  It was frustrating spending hours debugging only to find out the compiler wasn’t handing an instruction correctly.

This time I wanted to build a prototype fairly quickly and increase the budget to do so.  Moving motors from a computer has been done many times before and it has been broken up into modular components.  So, I only had to determine what I wanted to move and get that connected to one of many types of PC ports.

The type of motor I wanted to start with was a servo.  So, I did some searching on the web and located a reasonably priced Pololu Servo controller that receives commands over an RS-232 DB9 port.  Now, since most modern PC’s don’t have serial ports, I purchased a cheap USB to Serial adapter, the TU-S9.  The adapter would also be useful for other projects since the serial interface is fairly basic.  Since I already had a servo from Parallax, that was all I needed.
ServoController
Parts:

The TU-S9 is a nice adapter since it is built with the PL-2303 chipset and is supported on most Linux distros.  Once you plug it in your PC, you should see ‘/dev/ttyUSB0′ appear.  This worked without problems on my Ubuntu Netbook Remix distro.

The servo controller is nice, but I initially had some problems with getting the configuration right.  I started with a modified test application with a tcl UI (created for the 16 servo controller).  When that didn’t work, I moved on to a Python test script.  The servo’s didn’t budge with it either.  The only thing that worked was a .Net test application on an old Windows PC.  It was odd since running the Python script on that same PC wouldn’t work, even when the transfer signals were identical for both.

Since I didn’t have the source code for the .Net test app, I couldn’t find out what serial configuration could be different between the other applications.  At one point, I simply pulled out the default DTR/RTS jumper and gave it a go.  This ended up being the problem.  The .Net app must have handled the RTS line properly so that it didn’t reset the controller.  Wow!  I wish I tested the other RS-232 lines!

In the end I was able to whip together a simple python demo script (see below) that moves the servo to various positions.  Feel free to use it, I got inspiration from a previous test script.


(Wordpress doesn’t like source code. So bear with me.)
# servoDemo.py
import serial
import sys
import time

# Helper function
def setpos(n,angle):
#Check that things are in range
if angle > 180 or angle <0:
angle=90
# Must be between 500-5500
data = int(5000 * angle / 180) + 500
datatwo = data & 0x7F
dataone = (data >> 7) & 0x7F
buf = chr(0x80)+chr(0x01)+chr(0x04)+chr(n)+chr(dataone)+chr(datatwo)

# write the buffer then sleep for a while
ser.write(buf)
time.sleep(1)
### Main: script start ###

# set up the serial port
ser=serial.Serial()
ser.baudrate=9600
ser.baudrate = 9600
ser.port = '/dev/ttyUSB0'
ser.open()

# send some position commands and watch it move
setpos(7,30)
setpos(7,90)
setpos(7,180)
setpos(7,45)
setpos(7,135)
setpos(7,90)
setpos(7,45)
setpos(7,30)
setpos(7,45)
setpos(7,30)
setpos(7,45)
setpos(7,30)
setpos(7,135)
setpos(7,30)
setpos(7,90)

]]> http://half-byte.com/2009/09/20/servo-controller-driven-over-a-usb-serial-adapter/feed/ 0 How to: Laptop battery hack. http://half-byte.com/2008/12/27/how-to-laptop-battery-hack/ http://half-byte.com/2008/12/27/how-to-laptop-battery-hack/#comments Sat, 27 Dec 2008 23:11:06 +0000 nibble http://www.half-byte.com/2008/12/27/how-to-laptop-battery-hack/ Somewhat recently I bought an Acer Aspire One netbook and have been very happy with it so far.  However, one of the downsides is the lack of battery power.  This blog post shows you a DIY upgrade of your original battery.  Creating a battery that is 3 times the weight of the laptop seems to [...]]]> Somewhat recently I bought an Acer Aspire One netbook and have been very happy with it so far.  However, one of the downsides is the lack of battery power.  This blog post shows you a DIY upgrade of your original battery.  Creating a battery that is 3 times the weight of the laptop seems to defeat the purpose of a netbook.  But, regardless, it looks like a fun upgrade, especially for other old laptops that are dead because you don’t want to spend 50 bucks on a 10 year old computer.

]]> http://half-byte.com/2008/12/27/how-to-laptop-battery-hack/feed/ 0