SR2 Brown-out problem

[a.brooks]

Hi,

We use the SR2 on a number of mobile robots. After much tracking down of the problem, we have found that the SR2 occasionally browns out a small section of the motherboard, causing other components to fail. We're guessing that it's drawing a significant amount of power when this happens, and I'm wondering whether anyone else has seen this, and whether the motherboard is at fault or whether the SR2 is operating out of spec?

More specifically: the motherboards we're using are "Aaeon EMB-852T"s. The wireless card causes the UARTs on some of the serial ports to brown out and the PCI cards to brown out. The symptom in both cases is lost bits when they're talking to other peripherals. We have about a dozen identical motherboard/SR2 setups, and the problem is identical in all cases.

We've characterised the problem further: if the wireless card is inserted but disabled ("ifdown ath0" in Linux) the problem does not appear. When the wireless card is in normal use, the problem appears almost exactly every 5 minutes. I'm not sure what LInux might be doing every 5 mins. The problem can be brought on instantly by continuously scanning ("iwlist ath0 scan" in Linux). Continuously scanning like this causes the UARTS and PCI cards to be un-useable.


Does anyone have any ideas?


Thanks very much,

Alex

[UBNT-Mike.Ford]

Hello Alex,

How much power can that motherboard supply to the Mini-PCI slot?

Thanks,

MIke

[a.brooks]

Hello Mike,

Thanks for the reply. I asked the Aaeon people, they replied that the motherboard conforms to the mini-PCI spec, which states that, "the total power consumption from all sources is limited 2.0W" (Section 2.3 of the spec).

The Ubiquiti SR2 quotes a peak current of 1300mA@3.3V, which equates to a peak power draw of 4.29W. Does this mean that I have a problem?


Thanks,

Alex

[UBNT-Mike.Ford]

Hey,

Yes if the board cannot supply more then 2W, under full load the SR2 can cut out, or be significantly down in power, or even worse, reset the board.

Thanks,

Mike

[a.brooks]

It sounds like the SR2 will not work according to the mini-PCI spec -- so I need a non-standard implementation in order to use this card? Does Ubiquiti know of or recommend any motherboards which are able to supply sufficient power? Or do you know if it's possible to configure the SR2 somehow to work with the standard motherboards that we have?


Thanks,

Alex