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4 digit 7 Segment LED Display |
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Written by Aaron Brown
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Saturday, 08 January 2011 22:07 |
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After acquiring a large ( 26cm x 13cm) 4 digit 7 segment display, from George (M1GEO) and not wanting to unpack I set about making it work under linux.
The board contains a SAA1064 - an I2c 4 digit 7 segement display driver chip. Ideal for connecting to my bus pirate.
After much stumbling around and trial and error I managed to get it to light each segment. The notable points(errors) were:
- I2C is an open collector bus, meaning each device only pulls the data lines low. This meant that I had to turn on the Bus pirates on board pull up resistors, as for some reason the ones I thought were doing it on the board weren't.
- When using the bus pirates pullup resistors, the Vpu(V pull up) lead should be connected to +5V.
- The board requires a large voltage inorder to get the Led's to light, my initial attempts used the bus pirate to power it, but this was both too low current 125mA and too low in voltage for anything to light. I then connected it to an external power supply and found it lights best at about 12V although the chip does get a little warm :S (The data sheet claims it's good till 18V)
- The digits are counted from the right hand side(with the chip and sockets at the bottom).
The Digits are are as follows:
0 - 0xfd
1 - 0x0c
2 - 0xda
3 - 0x9e
4 - 0x2e
5 - 0xb6
6 - 0xf6
7 - 0x22
8 - 0xff
9 - 0xfd
Bus pirate:
I once it's connected the bus pirate need to be set to I2c mode i found the default 5khz speed worked fine for me. The pullups and on board power supplies are turned on by sending 'P\n' and 'W\n' respectively. Then to write to all the digits at once I used the following command:
[ 0x76 0x00 0xf2 d1 d2 d3 d4 ]
Where 0x76 is the device address (determined by a potential divider connected to pin 1 of the chip). 0x00 Tells it i want to start writing at the control register. 0xf2 Tells it to refresh all digits and I want them at maximum brightness. then d1,d2,d3,d4 represent the digits in hex.
Heres a picture of it working:
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Last Updated on Sunday, 22 April 2012 14:44 |
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PX264 - Physics of Fluids |
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Written by Aaron Brown
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Friday, 01 May 2009 09:49 |
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This module was taught by Mario Nicodemi in the second term and starts to introduce the the physics of fluids; introducing initally the bernoulli equation and then showing how this can be extended to get the Navier-Stokes equation which is believe to contain all the information required to explain turblence. If you can solve it for the full general case. ( I think this is one of the millenium problems, but i'm not too sure) |
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Last Updated on Friday, 01 May 2009 10:29 |
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Written by Aaron Brown
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Saturday, 25 July 2009 04:05 |
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After reading http://www.xkcd.com/413/ and purchasing an Eeepc i have always been meaning to get round to seeing how hard it would be to create something similar. so far all i've done is strip done an old 1:12th scale remote control car and create a PIC interface to the control it, which I plan to connect to the Eeepc via a USB to serial adapter. i then plan to write some software for both the Eeepc and a remote computer such that it can initally be controlled from the Remote machine, (via wifi or Bluetooth, not quite sure yet) With the Web cam from the Eeepc being streamed to the remote machine. I then plan to improve upon this by rewriteing the software for the Eeepc such that it can do some kind of basic collision detection using the images from the Eeepc's web cam. Although as of yet I am not quite sure how to go about doing this. Parts Used so far:- 1/12th scale remote control car
- PIC16f628a
- 4 Relays
- 4 BC547's
- DB9 F connector
- Usb to serial adapter
- Eeepc 701
- Various Resitors and Capacitors
- lm7805
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Last Updated on Sunday, 23 August 2009 00:07 |
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Computer Controlled RC car - Superceeded by the EEEPC buggy project |
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Written by Aaron Brown
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Monday, 09 March 2009 14:12 |
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One afternoon, while bored, George and I decide to modify an RC car so that it could be controlled from a computer. Making it into a sort of logo floor turtle thing. This was achieved by connecting the remote control via several relays to the computers parallel port. The user was then able to control the car via a program on the Computer. The program had 2 modes, an interactive mode in which it behaved in a similar fashion to Logo (a sort of basic plotting progam used in schools) and a command mode in which it would execute a specified command then exit, allowing the user to write a short shell script in order to automate a sequence of actions. Files: |
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Last Updated on Thursday, 20 August 2009 14:33 |
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