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jayos
Nou Venit
Joined: 03 Jul 2006
Posts: 1
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 Posted: Mon Jul 03, 2006 11:54 pm Post subject: Wire Connection Question?!? |
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before i start i got a question...
in the readme.pdf i read following:
"Prepare your technican PC by connecting the interface to the COM1 port (don't connect the wires to eeprom yet). Turn on Thinkpad and press F1.....connect the wires to the corresponding wired from the interface(attached before to COM1) and execute R24RF08."
Wouldn't it be much more easier to connect the 3 wires to the simple interface then turn on the thinkpad hit F1 and THEN connect the interface to the COM1 on your PC? |
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rkawakami
Interesat
Joined: 16 Apr 2006
Posts: 26
Location: San Jose, CA USA
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| Posted: Tue Jul 04, 2006 8:03 am Post subject: Re: Wire Connection Question?!? |
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| jayos wrote: | | Wouldn't it be much more easier to connect the 3 wires to the simple interface then turn on the thinkpad hit F1 and THEN connect the interface to the COM1 on your PC? |
Yes it would, from a mechanical point of view. What I mean by that is: it is logical to assume that you would tear down the laptop, afix the wires to the motherboard, connect them to the interface (simple or driven), re-assemble the laptop until it is in a state which you could power up with at least the keyboard and display working. Then connect the interface circuit to your "reading/decoding" computer via the serial port and power up your locked system. But what happens electrically is that your interface circuit is already connected to the EEPROM before you power up. It is likely that, with the simple interface circuit, you will interfere with the normal startup sequence and 1) prevent the laptop from POSTing, 2) put the EEPROM in an un-readable state or 3) (worst case) accidently change data in the EEPROM which will make your problems even worse.
I believe that the instructions are written such that it will minimize any damage you could do to the laptop/EEPROM. What would normally happen is that you would simply attach the three wires to the EEPROM (keeping them separated), re-assemble your laptop, power it on, wait unitl the laptop displays the lock icon (thereby allowing all of the normal signals to be applied and then remain in a steady state), then connect those three wires to the interface. That connection is typically done with small clips or simply by pushing the wires into your breadboard.
The simple interface circuit using the diodes is a "brute force" method of converting the signals inside the laptop to ones that can be used at the serial port of the reading/decoding computer. On the other hand, the driven interface attempts to properly match up to the laptop's signals and provide a "cleaner" way of performing the signal conversion.
By design, the simple interface circuit is just that; simple to make. There are tradeoffs that must be considered with any circuit design. The major one for the simple interface circuit is that even though it is simple to build, it may not work in all situations. The driven (MAX232) circuit has these tradeoffs: 1) It uses more parts, 2) it will definitely cost more to build, 3) there are more chances of building it wrong. However, it also has a greater chance of successfully reading the information out of the EEPROM simply because it is designed to work better.
For reference, read my page on building the driven interface circuit.
(edit: Added third paragraph. I think I got a little ahead of myself since I thought I had typed it in  ) |
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