Dean Fritz

Can any other 232 line drivers be used besides the MAX232? Can you use a MC1488N or a MC1489P? I know they wire up different but, will they work the same? I can obtain these IC 232 line drivers local. (Radio Shack)If so does anyone have a print to do this.

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Anyone read the datasheet for the MAXUM chips? at the bottom of each page it says "for free samples and info, call (800)......." There's that magic word, FREE! I need to practice my bulls**tting abilities and pretend that I'm working on some high-profile project that needs MAX232 chips.. I wonder how many they'll give me before suspecting something's wrong? "uhh.. yeah.. I need 20 of them, just to MAKE SURE they're exactly what I need.."

TomP

Dean, I wondered that myself, a while ago. Maybe I'll go digging in my old pile of computer/electronic papers this weekend... What's a MAX232 do anyway?

It must have some correlation to a 1488/1489, that's what's used in computers! Well, okay, that's what was used on the old RS232 boards, I'm sure things have changed. But the Max232's gotta be compatible somehow; otherwise, we'd also be building an interface board with a Max232 to put inside the PC.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

Dean Fritz

I don't mind ordering off the internet, but if I can find it local and it will work, I would prefer to obtain it local. Does anyone know if the 1488 or 1489 will work?

UnderDogRS

i have had 2 232 chips in my room for a year (other project) that they sent me **FREE** just goto there webpage and fill out the form
make up a B.S company and you get 2 in the mail.

HTH,
RS

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(A.K.A FireBird88)
AOL SN: Zander0710
1992 Camaro RS 25th anniversary edition Adopted Feb,14 2000

Mods:
14x3 Open element w/ K&N filter, MSD GM blaster Coil and 8.5 SC wires, AFPR, 60psi. Fuel Pressure gauge, 3-Row Al rad. , 180* t-stat, Hooker 1 5/8 headers, 3" Catco cat, 3" Hooker Aero Chamber cat-back, "Ultimate TBI" mods

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Just filled out the "free chip request" page, we'll see what happens! I asked for MAX232CPE and MAX232ACPE samples so hopefully I'll get 4 chips Now if only a ZIF socket vendor would give out free samples..

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Where are you guys getting you ZIF sockets from, and how much? Digikey has some that look like they'd work, listed ad a low-profile ZIF socket (P/N A346-ND). The website lists them as $6.03/ea. I don't expect them to be cheap but I'd sooner not waste $12 or so if they won't fit for some reason. (I never buy one of anything!) Anybody come up with a better deal, and a P/N for one that is known to fit good? Can ANY ZIF-socketed chip fit under the plastic mem-cal cover?

Dean Fritz

Gravitar,
I bought one from digikey and it was to long, it hit the ESC filter. I bought a 28 pin lo profile dip from radio shack and it fit perfect! It cost 59 cents and no shipping charges! If figured out of all those so called Electrical Engineers out there they could tell me if the 1488 or 1489 232 line drivers would work?

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If you're looking for an EE to answer, it would be my pleasure to give you an EE-type answer: THEORETICALLY it should work fine. Which is to say, I've never tried it but the 1488/1489 do a fine job of converting TTL to RS232-level, so I can't see any reason why they wouldn't do it in this application. Obviously though, it wouldn't be a "drop-in replacement" for the MAX232 in the circuits shown, you'd have to select a different set of passive components to interface the chip to your PC and ECM.

I think the reason why the MAX232 is preferred over the 1488/89 is the MAX combines transmitter & receiver functions in one chip, and best of all it can be done with a single 5V source. The 1488 requires +/-15VDC, which isn't too easy to find in a car! Now do we really NEED this capability? I don't think so, we're only receiving data from the ALDL pin, right? (I was trying to find the MAX232 ALDL schematic, I recall it actually using the transmit pins as well) If we can live with recieve-only (which makes sense to me), the 1489 wouldn't be too bad an option as it looks like it only needs 5VDC.

gravitar

BTW, is THAT what the middle chip is, a filter for ESC? Does the chip have an off-the-shelf equivalent or is is a GM ASIC?

I'm also finding out that the mysterious "limp-home" chip at the end of the memcal is nothing but a resistor network!

TomP

Gravitar, here's one schematic with pinouts, and it looks like you're right- receiving circuits aren't used. The 8192 "version" seems to block the recieving circuit with a diode... why, I don't know. Seems to me that could've just been left disconnected.

Unless, of course, the Tx and Rx lines were messed up. I had to create a specialized RS-232 interface cable at work, and I found at least 20 RS-232 diagrams that couldn't agree on Tx/Rx descriptions. And I wondered why my cable didn't work! Ha!
http://www.techedge.com.au/vehicle/aldl/8192/8192hw.htm



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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

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Yep, looks like our PC interface is "listen-only". On a related note, I used to have access to a Tech-I scanner, and just for fun, I plugged it into a number of late 80s/early 90s GM ECMs, to see what I could see. I swear, on some cars we were able to CHANGE things, not just SEE things! I think we were turning on/off the fan, fuel pump, maybe a few other things as well. Somehow, we must have set up a bi-directional link with that Tech-I. How? Does the ALDL have a Rx pin?!

Dean Fritz

Gravitar,

Did you find out anymore about the limp home chips? Are they just a resistor bank?