Megajolt Connectivity issues

[egret]

I've got a second hand megajolt on my car and it runs great, but I've never managed to have it to talk to a pc.  Always get a timeout reading cylinder count error.  Sometimes a timeout reading ignition confuguration briefly before too.

I know the usb-rs232 cables are a bit hit and miss, but the one I got from  RS seems to be good and I've got the megajolt software accessing the correct port, but still have the errors.  What's the opinion here, if I can see the port in device manager and it's consistent, is that sufficient sign that it's a good cable?

Windows 10 and MJLJ Configurator V4.0.2

Cable shows up as a USB-SERIAL CH340

[mpbarrett]

Check what handshaking, on the RS232 side, the Megajolt needs. Also you can play around with the data buffer size which can sometimes help and check the USB driver is up to date (worth going to the silicon manufacture to get the latest driver).
Usually the RS stuff is good, whats the RS part number?

mike

 

[Nick Jones]

Never tried with MJ but I can say that I’ve had variable results with MS with different RS232 - USB adapters. Varying from perfect, to flaky to not working at all.

Definitely a general correlation with cost (though I don’t suppose the RS one was particularly cheap!) and I’ve found the ones with FTDI chipsets to work better.

[egret]

Cable is this: https://uk.rs-online.com/web/p/interface-adapters-converters/1445699 RS part number: 1445699

I've played about with the data buffer size in the past with no sign of improvement.

One update is that in frustration I traced as much continuity on the board vs the circuit diagram as I could last night and have found that pin 8 of the megajolt MAX RS232 chip does not have continuity with the PIP connection on the main connector.  I'm going to scrounge some enamel wire and solder up a bypass for this to see if it works.  I can't actually work out why the RS232 connector needs to speak to the PIP directly, but then I'm not an electronic engineer and don't pretend to understand the complexities of it all.  

[Nick Jones]

Difficult to say anything definitive about the RS cable. The chipset isn’t specified

Didn’t find the statement “designed with customers in mind” in the product description especially confidence-inspiring.

I have no idea why pin 8 would be linked to the PIP either….

https://www.engineersgarage.com/max232-pin-out-and-description/

This says pin 8 is one of the 232 inputs though.

 

[egret]

To update this.  I had an issue with a broken track on the board whihc, once fixed, solved my problem.  I then flashed a new firmware to the megajolt and used th correspondingly aged megajolt monitoring software.  It all talked and worked fantastically until I shorted the coil feed to something.  I think this briefly shifted the relative voltages of the EDIS and Megajolt to rather different values and, because the pip signal into the megajoly processor is not protected in any way, damaged the chip.

The good news is that trigger wheels still sell the processors, so I've one of those coming in the post and should hopefully be a relatively simple swap to get it working again.  In the interim, I'll be paying more attention to my loom and making sure it's me-resistant, if not actually foolproof.  I'll let you decide which is more onerous!

[Nick Jones]

11 minutes ago, egret said:

I'll be paying more attention to my loom and making sure it's me-resistant, if not actually foolproof.  I'll let you decide which is more onerous!