dLink Broken?

[nitneylion452]

Our dLink seems to be broken, or at least, malfunctioning. We lose communication every few seconds for about a second each time. It's enough to interfere with performance, but not cause the robot to disable. The same has happened a couple of times while tethered to the dLink as well. We have tried multiple computers to eliminate the possibility of a defective WLAN or LAN adapter. Any ideas on why this may be happening? Thanks in advance.

EDIT:
We also checked the power regulator, and it seemed to be working fine, putting out 5.0V. But even so, I don't think that can be the issue because the power cycle time of the dLink is ~1 min and we are only losing communication for less than one second. Also, Windows sees the network and says we are connected. I have tried pinging the network and had 0% packet loss in about 30 pings.

[Mark McLeod]

Lots of possibilities, the DLink malfunctioning is only one of many.
For example:

• Check the Driver Station CPU utilization to see if it's overloaded and slowing down. Cntl-Shift-Esc, then performance tab to check PC CPU utilization.
• Check the cRIO CPU load as well. The method depends on what programming environment you're using.
• Poor connections/cable between the cRIO port and the DLink.
• You can also check out this recent thread on a purely wireless potential cause, and there are other wireless reasons for problems like this that don't mean your radio is broken.

I'd continue to isolate the problem by eliminating the DLink from your tests by tethering your Driver Station directly to the cRIO port. That would check all the other non-DLink related potential causes.

[skimoose]

If you are only losing communications for a half second occasionally, it's probably found in a poor connection between the dLink and cRIO. Check or replace your CAT5 wiring.

If it was a loss of power or an under voltage issue, the dLink takes about 40-45 seconds to reboot and re-establish comms. This can be the result of loose connections in your wiring or more likely a poor connection at the dLink barrel power connector. These power jacks are pretty poor quality and we've started duct taping our power connector into the dLink to insure proper connectivity. The other reasons for the dLink losing power are the voltage converter failing or not correctly wiring the voltage converter to the regulated power port and using any WAGO power port through a snap action breaker. These radios seems to be very susceptible to voltage sags. If the battery is getting low or the voltage regulation isn't doing its job, a voltage drop will knock the dLink off line.

We've had one dLink actually fail at Championships. After our radio began knocking off line mid match and getting progressively worse each match, we ran through every possibility I mentioned above. We finally swapped in a loaner radio from another team and the issue went away. That trouble shooting cost us three matches of going dead and sitting there for 45 seconds hopelessly waiting to re-establish comms.

When our team returned home, I opened the dLink to search for the cause of our problems. Under magnification I found a surface mount capacitor with apparent cold solder joints. One side had broken free from the pcb and when I barely touch the component it fell off. These units are manufactured in China and the board does not appear to be wave soldered but hand soldered. Looking at the components under magnification many are not lying flat on the board and are not uniformly placed on their pads. So while the cRIO will handle a 50G shock load I don't think these radios are quite as robust.

We had another radio on our practice robot begin to have similar issues after one of our students accidentally drove at full speed into a tower base. I opened that radio to look for similar bad solder joints but didn't find any. There was a distinct smell of "magic smoke", but the radio was clean with no foreign matter inside the unit which could have contributed to a short.

I hope my problems are isolated issues. As far as I know, there haven't been many reports of failed dLinks, but if others are having problems, we should probably let Kate know up at FIRST HQ.