MS2/Extra manual index

Getting correct serial communications between your computer and Megasquirt is critical to enable tuning.

Almost all reported user problems are actually a computer setup problem, so follow these steps to get your settings right.

1. Serial connection identification.

The Megasquirt serial port

Standard DB9-DB9 straight through serial cable:

Computer DB9 serial port

Computer USB ports

Typical USB-serial cable:

2. If you computer does not have a standard serial port, as is the case with many computers over the last few years, then you probably have USB only and will need a USB-serial adapter cable.

3. If you are using a USB-serial cable then ensure you have installed the drivers (if required) before plugging in the cable for the first time.

3. Open Device Manager on your computer.

There are several ways to do this, and you may have a preferred way. If you don't know how to do this, here are directions for getting into the Device Manager for XP and Vista.

On Windows XP, right-click My Computer and select Manage. This will bring up the Computer Management screen. Select the Device Manager from the list at the left.

For Vista, click the Start button and go to the Control Panel. From there, click System and Maintenance, then click on the Device Manager from there. You may need to enter a password.

If you DO NOT see "Ports" listed in the devices then you do not have any ports setup. This would usually indicate either your forgot to plug in your USB-serial cable or there is a driver problem. Usually the best solution to the driver problem is to unplug the cable, uninstall the driver and then re-install the driver.

4. Take a note of the COM port number listed above. In this case it was COM1. Most drivers allow you to change the com port number. Set to COM1 if it is free.

5. Use this COM port number when setting up your tuning software.

6. Hopefully that should be sufficient to get you connected, if you still experience difficulties, there are additional tests to try.

Additional diagnostics

7. Start TunerStudio (or other tuning software) and open Communications -> Miniterminal. Ensure your Megasquirt is powered and connected to your computer.

Select the port as above

Select the baud rate.

MS2 = 115200

MS1 = 9600

Click to Open the port.

8. Type a capital 'S' and you should see a signature string returned in the lower window as shown here. If you do not then there is a serial problem somewhere.

9. Unplug the serial cable from the Megasquirt and carefully short pins 2 & 3. This performs a "loopback" test where the serial signal should go out from the computer, through the short and back into the computer again.

10. With the pins shorted as above, type in something to Miniterminal. Whatever you type into the top window should appear in the lower window. As shown here this indicates the computer serial end is working ok.

11. If test 10 fails then you have a serial driver problem on your computer - consult the documentation that came with the computer or cable.

12. If test 10 passes but test 9 fails, there might be something wrong on the Megasquirt end of things - consult the support forums or your reseller.

13. If tests 9 and 10 pass but you are having problems with the tuning software, it is most likely a settings problem within the tuning software itself. Double check the COM port and baud rate.

If you have a question, comment, or suggestion for this FAQ please post it on the forum.
Last Updated: 10/07/2009 15:45

No part of this manual may be reproduced or changed without written permission from James Murray, Ken Culver and Philip Ringwood.