Service Forum

semaj · Interesat Joined: 16 Dec 2005 Posts: 15

i am trying to get the pinout for 232 chip to db9 connection. I cannot find the a correct one anywhere.

i also cannot find the driven-i2cprog.pdf file

victor · S.F. Boss Joined: 07 Mar 2004 Posts: 2546 Location: Staff

Download the reader or writer kit and install. The documents are included there. Also you may want to read the practical guide written by wolfman here

semaj · Interesat Joined: 16 Dec 2005 Posts: 15

ok i found the file thanks
i tried this setup and reader said could not find eprom
i am going to rework th circuit again
what would the correct voltage be if i used the max232 or 233 chip ?
i used 4.5v like i saw in victors directions, and there is 5v stated for the old guys method?
also what is the correct sequence?
victor says
ibm laptop->chip->eprom reader
in the old guys post i saw
chip->ibm laptop->then eprom reader

also how long is too long to have power to the chip so it is not fried?

we are checking connections, replacing chip with another one that is working, checking solder points, and plan to resume this monday night. wish us luck

this is all being done on an ibm t41

victor · S.F. Boss Joined: 07 Mar 2004 Posts: 2546 Location: Staff

All I can say is: read carefully the tutorial and other posts.

wolfman · Posted: Mon Dec 19, 2005 6:33 pm Post subject:

The 5v on the schematic is nominal, Victor's design uses 3 1.5 AA batteries and so the actual is 4.5 V. If you have a 5V source you could use that instead of the batteries, .5 volt doesn't make a difference in this circuit.

As far as the sequence, I don't think my description and Victor's are different. In each, you power up the laptop and wait for it to pause at the password input prompt. You have the circuit connected to the other computer's serial port. If using the driven circuit, you have it powered at this point. Then you connect the circuit to the security chip in the laptop and run the eeprom reader program, then disconnect from the security chip, then power down the driven circuit (if used), then run the decoder against the saved bin file.

Victor's material has extra precautions about the order of connecting the SDA, SCL, GND wires from the circuit to the security chip.

By "power to the chip" do you mean power to the driven circuit and the Maxim RS232 chip? I've left mine powered for minutes at a time whilst the laptop was powering up and down. I made and remade the circuit several times to get it right and so the chip was powered a lot--didn't seem to have any ill effect as it worked in the end!

If you mean powering the security chip, it is of course powered every time the laptop is on; the connections from the circuit don't power it. I've left them connected for a few minutes at most, but again I did it a number of times to get it right.

Good Luck!

wolfman · Posted: Mon Dec 19, 2005 6:45 pm Post subject:

Easy DB9 connections

Only other thing I did to make it easy was used a pre-built modem cable that had molded pin #'s on the exposed face (needed a magnifier, but they were there). I cut off the other end and stripped each of the nine cables.

Then I took a stiff wire (piece of resistor leg) and stuck it in the port # specified in Victor's schematic and traced the nine wires until I found which one was connected to each port. I soldered a piece of rigid wire to each of the four (stranded) signal wires so I could insert them in the breadboard sockets and taped the other five wires out of the way (after trimming off their exposed wires-don't need any shorts!).

I marked the colors I found on my diagram, but don't know if they are universal.

This avoids all the problems of making good connections in a DB9 shell and figuring out if the numbers are from the front or back, etc.

semaj · Interesat Joined: 16 Dec 2005 Posts: 15

should the serial port, pins 7 and 8, 6 and 4 should be connected.
Take a look at this site 2nd picture:
http://lnx.manoweb.com/astro/telescope/cable/?partType=section&partName=serial&lang=en

the cable that we used also has those pins connected to each other.

victor · S.F. Boss Joined: 07 Mar 2004 Posts: 2546 Location: Staff

The cable you mentioned has nothing in common with the i2c schematics here. I don't see any link with what you really need to build.
It is easier for you if you could take a db9 female, a band of 4 tiny wires and make the cable in minutes. Or you could take a straight serial cable (coming from an external modem or so), cut off one end and adapt to the interface, like wolfman stated before

semaj · Interesat Joined: 16 Dec 2005 Posts: 15

i am also getting a crc2 error
i am still having problems with reading the eprom
will try to work on this more tonight

semaj · Interesat Joined: 16 Dec 2005 Posts: 15

could this setup also be accomplished by using a max233 chip
our schematic is below
http://www.lakesemaj.com/files/max233.pdf

victor · S.F. Boss Joined: 07 Mar 2004 Posts: 2546 Location: Staff

The circuit there has 2 problems:

1. No need to use two power sources. Just connect the max233 Vcc and the Vcc ends of the 2 resistors togheter.
2. The db9 pin layout is wrong?

semaj · Interesat Joined: 16 Dec 2005 Posts: 15

I used the information on MAXIM's website to "translate" your circuit to a circuit with a max233 chip. Here is the partial pdf file I used to match up the pins:
http://www.ogi.lakesemaj.com/temp/maximics.pdf
What did mess up?
Thanks for all!
By the way, I was able to find a store that sells max232 chips. I bought one and will build your circuit now. It would still be nice to be able to get this working with the max233.

bob · Posted: Fri Dec 23, 2005 10:36 am Post subject:

Depending on how you interpret the DB9 view in your diagram, the connection may be wrong. The COM signals are noted for each pin in driven-i2c.pdf, just check to be sure.

Please, don't open multiple threads on the same subject

semaj · Interesat Joined: 16 Dec 2005 Posts: 15

we are abandoning our driven circuit and trying the siprog setup. I am still in search of a local company in cleveland, ohio that sells the 20 cent zenor diode. i will give update after that .

wolfman · Posted: Tue Jan 03, 2006 3:46 pm Post subject:

Too bad you're abandoning the driven circuit, I had great success with it. See my notes under the sticky subject "[Practice] Making a breadboard out of driven circuit diagram" and feel free to email me with questions.

About local sources: I list some in my message; Victor doesn't want us to post direct links on the board, but in Cleveland that place that sells Radios in Shacks certainly sells diodes. Read my message and add a .com to the names and you'll be in good shape, I also list some part #'s.

Good luck and good soldering!