Hi,

I have a new customer with an interesting project:

At remote sites, there will be a RB411UAHR tunnelling back to a central concentrator. The RBs will be connected to the Internet via a GSM modems and a black box device will be connected to each RBs Ethernet port. That is the only equipment at the remote site.

The black box runs from a 12V supply and is very unreliable. There is therefore a requirement for forcing a remote power cycle of it.

So, I would like some way of using the RB to switch a relay which would then be used to cycle the black box.

I can think of several ways of doing it if I use external hardware (the best of which would be an Arduino monitoring the serial port), but it would be nice to be able to do it without any additional hardware (apart from the relay, of course).

Any ideas anybody?

Hmmm. Looks like I can set DTR and RTS on the serial port, so I could use that with a much less complicated microprocessor configuration. I'll get the multimeter out tomorrow and have a poke about to see what happens....

Hmm.

Setting DTR and/or RTS high and low seems to have absolutely no effect at all.

Ideas anybody?

OK. Problem solved.

I couldn't find any nice way of getting signals out of the board, so I've decided to use the serial port instead. Creating a special-user and then SSHing into the box works a treat.

I've built a proof of concept Arduino based prototype which offers a simple menu on a serial port and allows for triggering a relay which causes the attached kit to power-cycle. Total cost (excluding the RB itself), £20, so pretty cheap as well.

The down-side is that there's no obvious way for the Arduino to act as a watchguard unless the attached kit can send it a heartbeat. I'll have a think about this. It would be nice if ROS could send text out on the serial port of the RB itself, but that may be asking too much.

Why not set up a PPP server on the serial port ?

if you send FF 03 at it occasionally, the PPP server will send you loads of stuff.

Better still, implement the LCP bit of PPP and 'talk' to it - once LCP is up, the PPP server will keep sending LCP 'pings' once in a while.

How about using fan control for control signal?

Give Baltic networks a call..
www.balticnetworks.com
Thet are showing off a USB based digital I/O and temp / humidity sensor board at the MUM.