MX3660 and Gigabyte E350N

This is mainly a record that google will index so someone in the future will not suffer like I have. You're all welcome. This doesn't quite fit in this subforum but it doesn't really fit in any subforum without breaking it up.

1) The Gigabyte E350N that everyone talks about is truly a fabulous motherboard. The latency is < 4000. Until you load the AMD fglrx drivers and then whenever opengl is loaded the latency will spike to 30-40k. The best longterm solution is to use the radeon drivers from the linux kernel but on Ubuntu 10.04 those drivers do not recognize the graphics chip on the AMD cpu. When linuxcnc upgrades to 12.04 they will be.

So the next best solution is to load the older fglrx drivers. I started with the newest available on AMD's website (13.12) and they don't even compile. Then I started with the oldest (12.1) and they worked. But they have the issue with the latency spiking when opengl is started. I then worked my way up until I found a version that didn't. That version is 12.10.

There is a second problem though, if you load *2* instances of opengl (ie two glxgears) the first one won't change the latency at all, the second instance will spike the latency. I worked through all the drivers on AMD's website and they all do that. The good news is it doesn't matter. Axis only launches one instance of opengl and as long as you're not watching a movie or playing video games on the machine while the mill is running you'll have no issues.

2) I bought the MX3660 from leadshine. It's an integrated breakout board and set of 3 digital 6 amp drivers. It has all the features I wanted and is a pretty cool little board. As always, something has to be wrong with it. It will send errors back over pin 15 so linuxcnc will know that it had a fault. I set this up and then got random "estop-reset" errors where linuxcnc would be in the off state because the MX3660 would send a fault. These would happen at totally random times. While the mill was running a program, while it was sitting idle, just totally random. Sometimes 5 times an hour, sometimes once every hour.

I spent a week trying to solve this but there is very little information on the MX3660. I was using properly shielded and grounded cables (ground only the end at the breakout board). The manual said it would only fault if one of the drivers faulted but the driver fault lights would never flash. I doubled my step and duration pulses and that seemed to help. The real answer though is the board only likes 5 volts from the parallel port. The parallel port built into the Gigabyte motherboard only puts out 3.3V and while Leadshine's manual says the MX3660 can take 3.3-5v inputs I assure you it likes 5 volts way better. I bought a 5v parallel port card off amazon for $12 and that solved all my "estop-reset" errors. I have successfully done over 12 hours of milling without a single estop-reset error.

Thanks for your info, may save someone else a lot of time.

I had not seen the MX3660 until you highlighted it
It really is an all in one unit, even has a speed control output for the spindle
Could be very usefull where space is limited

Given that it incorporates a BOB, presumably opto isolated, it is suprising that they did not buffer the inputs to 5v
There has not been a PC made in the last 10 yrs or more that did not have a 3.3v parallel port (those that even have them that is)

regards

Given that it incorporates a BOB, presumably opto isolated, it is suprising that they did not buffer the inputs to 5v

It don't think it is opto-isolated. All the datasheets from Leadshine are silent about optical isolation except the 0-10v analog output for the spindle speed control, that is opto-isolated.

The problem is it works, 99% of the time with a 3.3V output but that last 1% will drive you nuts. Perhaps the gigabyte motherboard puts out 3.2V or something just a little low. If Leadshine wants to redesign the board I would highly recommend they add buffering so it works 100% with 3.3V.

Also, I installed ubuntu 12.04 with the rtai 3.4.55 kernel and I'll be including a writeup on that in a couple days. It seems to work well, I just want to test it more.

For systems like this that have parallel port voltage sensitivity problems Sherline makes a nifty little port voltage booster that gets power from a nearby USB port. I think the model number is 8770 but not sure. Costs around $50 and is just a simple plug in deal that works extremely well.

Also, I installed ubuntu 12.04 with the rtai 3.4.55 kernel and I'll be including a writeup on that in a couple days. It seems to work well, I just want to test it more.

That is the way to go, the 3.4.55 kernel at least, I have had it with Ubuntu.
It works well and you have newer drivers and better hardware / chipset support.

I have been running a 3.5.7-rtai kernel on Debian for over 8 months now and all the stupid issues with video modes and monitor / video card recognition I had with the 2.6.32 kernel, just vanished.

regards