No serial connection/not detected

[Matterx]

Hi guys, newbie here, still in the process of assembly.

PCB V3.0
MS-I processor
Hall Circuit
Cablemax USB Serial Adapter
(Anything else you need, let me know)
Ordered this all from DIYAutoTune

Everything was going swimmingly, passing all of my tests during assembly. I got to the point where I could adjust the knobs on the STIM and see results in Tunerstudio.

I went to move on to the next phase of assembly the following night, but thought I should plug in the stim again and re-create my results from the night before for good measure, and, surprise surprise it wouldn't connect! No matter what I tried, it wouldn't connect or detect the ECU anymore. I honestly did not change a thing; it just 'decided' the next night to stop working.

I ran all of the assembly tests again, passing them all, then moved onto the troubleshooting guide (http://www.megamanual.com/ms2/V3trouble.htm), and passed all of the serial port tests here too. I was able to find another, new MAX232 chip, and, just on the off-chance that I'd managed to ruin the first one somehow, I clipped out the old one and soldered in a new one, same problem (even though admittedly my solder job on the new one isn't quite as pretty).

Now I'm at a complete loss and I need to know where to go from here. What else should I be testing? Anything on the stim I should be paying attention to?

I've been at my wit's end for days here. Any help is greatly appreciated, thank you!

[Bernard Fife]

Matterx,

You might want to check out the serial comms connection troubleshooting guide here: http://www.megamanual.com/connect.htm#ms1

Lance.

[Matterx]

Hello Lance,

Thank you for your timely response to my issue. I apologize that my own response has been more than a month in a making -- I've been fighting some illness for a while, and just finally was able to get back into my workspace to diagnose the MS-to-be.

I tested all of the circuits listed in the assembly instructions, along with all of the ones in the link you sent me, and everything is checking out just fine...

... except, I can't get a successful loopback when I jumper pins 12 and 13 on the CPU. Any thoughts?

[Matt Cramer]

Hello Lance,

Thank you for your timely response to my issue. I apologize that my own response has been more than a month in a making -- I've been fighting some illness for a while, and just finally was able to get back into my workspace to diagnose the MS-to-be.

I tested all of the circuits listed in the assembly instructions, along with all of the ones in the link you sent me, and everything is checking out just fine...

... except, I can't get a successful loopback when I jumper pins 12 and 13 on the CPU. Any thoughts?

Dead MAX232?

[Matterx]

Thank you for your response Matt.

A dead MAX232 was my initial conclusion as well, so I ordered a replacement and soldered it in. Same results.

[Matterx]

Gentlemen, I think I might have missed something.

I'm going back and rechecking everything (don't ask why it takes me weeks at a time to find time to work on this ), and I'm noticing that the voltage readings I'm getting on the MAX232 are not quite right.

I'm showing 7.32 volts on Pin #1 (on the MAX232) when tested against grounds on Pins #2 and #19 on the CPU

AND 3.52 volts on that same pin when tested against the ground on Pin #32 on the CPU

Specifications say it should be about 5 volts on all 3 counts, right?

Have I found my 'smoking gun?' and how do I rectify this? Can I?

Thanks for your continued support.

- Matt

[trakkies]

What do you get here:-

"You should check that you have 5.0 Volts (±0.10) on the MAX232 pin 16, and ground on pin 15. Use the middle pin of the voltage regulator as a ground for measuring the voltage, and check that you have less than 1 Ohms resistance between pin 15 and the center lead of the voltage regulator".

If there is a poor ground to one or more pins on the CPU, that is a separate issue. First, you need to get the loop back test working with the CPU removed.

[Matterx]

When tested against the ground on the center pin of the voltage regular, the readings on the Max 232 come back perfectly normal. Same when I check on pins 15 and 16.

Resistance between the center pin and pin #15 on the Max 232 is less than half an Ohm.

[trakkies]

When tested against the ground on the center pin of the voltage regular, the readings on the Max 232 come back perfectly normal. Same when I check on pins 15 and 16.

Resistance between the center pin and pin #15 on the Max 232 is less than half an Ohm.

Right. Move on to removing the CPU and linking pins 12 and 13 on the CPU socket with a bit of wire. If possible, use a computer with a real serial port to eliminate the USB to serial converter - which are often the source of problems. And do the loopback test.

[Matterx]

When tested against the ground on the center pin of the voltage regular, the readings on the Max 232 come back perfectly normal. Same when I check on pins 15 and 16.

Resistance between the center pin and pin #15 on the Max 232 is less than half an Ohm.

Right. Move on to removing the CPU and linking pins 12 and 13 on the CPU socket with a bit of wire. If possible, use a computer with a real serial port to eliminate the USB to serial converter - which are often the source of problems. And do the loopback test.

Uggh... except I was a major major dolt during assembly and just soldered the CPU right in there before I even noticed there was a socket I could have installed.