Service Forum

[LLED]

Just wanted to say thank you for a great service that this site is providing to the people.

I am building my breadboard following wolfmans sticky: http://www.allservice.ro/forum/viewtopic.php?t=123

I am not sure exactly which DB9 interface I should be building, should I follow simple-i2cprog.pdf or driven-i2cprog.pdf from : http://www.allservice.ro/forum/viewtopic.php?t=47

Please let me know if anybody has HQ pictures of their setup ( as I am not too knowledgeable regarding circuits ).

Thank you in advance

[rkawakami]

If you have read the entire thread at:

http://www.allservice.ro/forum/viewtopic.php?t=123

then you should have seen that there are some errors in wolfman's photos of his MAX 232 driven circuit with respect to the layout of the diodes. Also, near the end of the thread (top of page 2), I have posted a link to my site at:

http://www.rkawakami.net/ibm_600x/max232_if/

which should have the high resolution photos of a breadboard circuit that are you requesting.

My suggestion would be to use the MAX232 interface as it should work more reliably then the simpler zener diodes.

[LLED]

Thank you for the info, great site very detail oriented which is exactly what I was looking for.

Quick question, do you have an idea of a chip tester? Basically an inverse of the chip with connectors that I don't have to solder or touch a wrong connection by mistake of the eeprom.

Thanks again

[rkawakami]

Test clips which contact all the pins are made for the TSOP (thin, small outline package) devices like the 24RF08 EEPROM, however they generally cost from $75-100 on up. Are they worth it for a "one-time" situation? That's up to you to decide if it's cost effective enough. Using a clip is certainly safer than trying to solder two (or three) wires onto the fine-pitch lead spacings (ground can be attached almost anywhere there is a screw hole in the motherboard; if in doubt, use ground on the EEPROM). There are also tiny "grabbers" or "grippers" that can be used, one on each leg of the device. These cost much less (about $20 each). A couple of examples:

http://www.tequipment.net/ProbeMasterSMMicroTipProbe.html
http://www.emulation.com/catalog/off-the-shelf_solutions/debugging_accessories/microgrippers/0.5_0.2/

Using the full-chip clip or the grabbers still means that you must have the room to connect these clips while still being able to power up the motherboard.

However, there is another alternative. If you can manage to find out where the SDA and SCL pins are connected elsewhere on the motherboard, then you can solder onto a larger component such as a chip resistor or capacitor. This requires the proper equipment (a multimeter), some time and some luck in figuring out where those points are.

If you end up having to solder the wires directly onto the EEPROM, then I would suggest that you first apply a tiny amount of molten solder onto the bare wire. Then when cool, place the wire on the leg of the EEPROM and then apply heat with the tip of the soldering iron for only a second or two. If you have to repeat the process, give a few seconds for the EEPROM to cool down before trying to heat the wire/leg again. I have used this technique a couple of times without any problems. Check your connections with a magnifying glass before powering up the motherboard.

[LLED]

Again, thank you for this info, you have give me many different options.
One last Question: The positive and negative connection to the breadboard are located all the way on the top and bottom horizontal inputs?.

Thanks again for your responses

[rkawakami]

[LLED]

I have created the breadboard/db9 connection and power for 4.5 Volts.

Does anything look out of the ordinary? ( The green wire near the resistor goes to the ground on the eeprom)



Thanks

[rkawakami]

(Sorry for the delay... I could not post this as there was a problem connecting to the site.)

Yes! You appear to have the battery polarity REVERSED! Do not apply power until you fix the circuit otherwise you may destroy the MAX232. To fix it, simply swap the red and black wires from the batteries.

Also the blue wire that goes to the DB9 connector is not in the correct hole. It should be connected to pin 14 of the MAX232. Move it one over to the right.

The green wire you mentioned (near the resistor) will NOT be connected to the interface circuit ground once you swap the wires from the battery. That resistor is actually going to be connected to +4.5v. The other green wire at the bottom of the picture WILL be connected to the circuit ground and can be used to connect to the laptop ground, again, once you swap the battery wires.

Once you have made those changes I believe that everything should work.