Service Forum

joblinger · Nou Venit Joined: 07 Apr 2009 Posts: 7

Ok so i have been reading all kinds of smart stuff here Smile

Ok so I'm resetting the password on dell latitude D510 which has the 420 eeprom. I know noticed that you mentioned that i need to use a driven i2c programmer to read it. Ok I'm going to build that reader off of this schematic here

http://www.allservice.ro/forum/dl/driven-i2cprog.pdf

I was looking at the schematic and it shouldn't be to hard to build other than the fact that i cant find some of the parts. ill save my questions till the end so they aren't all over the place.

1. Are all these parts sold at radioshack? went to radioshack and they dont have 232 chips. I know i can get the resistors and diaodes and capcitors at radioshack. Anyone know a website i can order these in america? I found this one but there are so many MAX232A chips dont know which one to buy:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1798/t/or#f

2. On the diagram i noticed that the SDA coming from the eeprom to the max 232a has a branch for VCC. That is only needed if it not in computer?
3. Are the all the ground connecting to the DB9 Female connector to ground on reading computer?
4. Are the connection points to the right in the link above of the 24RF08 with 8 leads the same on the 24CXX?

Another question (dont have to answer) how exactly do you figure out the ohm rating needed for a chip?

All of your help is greatly appreciated!!

bob · Posted: Tue Apr 07, 2009 3:09 am Post subject:

Hello,

1. Any MAX232A, N, CPE or else would be just perfect. MAX232 not MAX220..

2. The branch you mentioned connects to the Vcc, all Vcc's goes together and in the diagram theres no need to show a line between "branches" since they are all Vcc by notation.

3. All ground come together, the COM port pin#5, the IC ground, the eeprom ground and the other grounds you may concede...

4. Yes.

5. There's the Ohm relation, if we want some maximum current to be absorbed for about 4.5V. ...Kidding, is just aproximated by the eye, really.

Have fun

joblinger · Nou Venit Joined: 07 Apr 2009 Posts: 7

Thanks a lot bob you really helped me out. And if anyone comes looking at this page for later reference here is a picture of the 420WP (24CXX) chip

http://img170.imageshack.us/img170/4336/i2ceeprompinshs2.jpg

bob · Posted: Tue Apr 07, 2009 3:18 am Post subject:

To read the 2402WP you may use R24C02, it works with the interface.
www.allservice.ro/store/utils/24c02.rar

joblinger · Nou Venit Joined: 07 Apr 2009 Posts: 7

So could i use this sample from maxium?

MAX232AEJE or MAX232ACPE+?

joblinger · Nou Venit Joined: 07 Apr 2009 Posts: 7

ok so i got the chips and having little trouble with schamatic. Here is a link to the diagram with my question about it. If someone could help me with the last part it would be greatly appricated.

bob · Posted: Tue Apr 14, 2009 10:02 am Post subject:

up-left square: They are all together
up-right sqare: Yes.
down square: Oh, yes.

joblinger · Nou Venit Joined: 07 Apr 2009 Posts: 7

so does that mean i got the wrong chip then if they dont have pins on the end of the chip? i only have them down the side of the chip.

victor · S.F. Boss Joined: 07 Mar 2004 Posts: 2581 Location: Staff

Does it have 16 pins in two rows?
then search DIP-16 on google...
_________________
Victor Voinea
ALLservice HQ, Romania.