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Megasquirt connectivity problems
novacaine - 26/8/08 at 09:32 AM

im having a few problems sorting my megasquirt kit out,

The circuit has passed all of the first tests so it is powered, but i am haing trouble getting it to communicate over the RS232 port.

THIS is the data sheet for the RS232 chip that is on the BOM but digikey have a 1,000 minmum order qty,

so, i have bought THIS alternative (See the diagram on the bottom of page 10, its the MAX202)



I cannot get the circuit to pass the tests that use hyperterminal (you know, if the letters that you type appear on the hyperterminal screen then everything is ok)

its not the cabe or the usb adaptor im using as when i jumper pins 2 and 3 of the cable the letters typed appear on the hyperterminal window.

all the solder joints appear to be fine, ive already gone over again to make sure,

i have replace the chip (bought another one from maplin and used an antistatic wrist band in case i destroyed the first)

but no joy,

im starting to get a bit frustrated, its only 4 caps and an IC,


oh and to add to all of this i have checked all of the following off the megamanual website troublshooting connectivity

Check on the MAX232 (U6) that you have:

5 Volts on pin #16,
ground on pin #15 (less than 1 Ohm from pin 15 of the MAX232 to the center pin of the voltage regulator).
Then check the continuity between:

pin 12 of the MAX232 to CPU pin 13 (RxD-1)
pin 11 of the MAX232 to CPU pin 12 (TxD-1)
Both of these should be under 1 Ohm. Check that you have 5.0 Volts on pin 16 of the MAX232. Also check that you get less than 1 Ohm from pin 15 of the MAX232 to the center pin of the voltage regulator. If those are good, then suspect the MAX232 itself.



The only thing i can think of is that the chip is the wrong one but the data sheets seem ok,


sorry for the long post

thanks

Matt

Paul TigerB6 - 26/8/08 at 09:44 AM

I had problems connecting to a MegaJolt and it turned out the problem was the Sony Erricson phone software on my laptop. Just an idea if you have the same software.

GregSL75 - 26/8/08 at 10:41 AM

I had similar problems with my USB adapter and Hyperterm IIRC, try downloading Megatunix and connect with that. http://megatunix.sourceforge.net/

MikeRJ - 26/8/08 at 10:46 AM

Your test on the cable does not rule out the cable being the wrong type. There are two main types of serial cable, pass-through and crossover (or null modem). You need a pass-through cable that connects pin 2 to pin 2, pin 3 to pin 3 and pin 5 to pin 5. Check with your multimeter.

Just to check, have you installed the temporary jumper between pins 12 and 13 of the microcontroller socket? If not then the loopback test will always fail.

novacaine - 26/8/08 at 11:33 AM

yea, it is a straight through cable, and pins 12 & 13 are jumpered

I dont have any sony ericson software, and i am downloading megatunix as i write this

thanks for your help so far guys, still scratching my head on this one

the_fbi - 26/8/08 at 12:18 PM

I may be talking cr*p here, but doesn't it need to be a MAX232 not a MAX202?

FYI - Maxim do FOC samples which you can request from the product page on their website.

novacaine - 26/8/08 at 01:26 PM

quote:
Originally posted by the_fbi
I may be talking cr*p here, but doesn't it need to be a MAX232 not a MAX202?

FYI - Maxim do FOC samples which you can request from the product page on their website.


thats what I was thinking but the guy in maplin seemed to think it would be a suitable replacement when i told him what it was for and showed him the datasheet for the original component

oh, and thanks for the tip on the free samples, ive just ordered a max232, see if that works

thanks

martyn_16v - 26/8/08 at 04:35 PM

quote:
Originally posted by novacaine
the guy in maplin seemed to think it would be a suitable replacement


I'd hazard a guess that the guy in maplin based that on the fact that they're both black and have 16 legs. They don't tend to employ people who can count much past 10 without removing their socks

turboben - 26/8/08 at 05:40 PM

I'd try to eliminate the usb altogether and test using the basic serial cable on its own.

mark chandler - 26/8/08 at 05:44 PM

Mine was a PITA when first trying to comunicate, hypertreminal failed, I downloaded teraterm which finally got me in. Once connected for the first time they all worked.

Regards Mark