toddf was groaning on irc one night about the high cost of remote rs232 access to servers. he then found a usb rs232 chip for < $3 and was wondering of a way to be able to use that remotely
i got into the discussion because of my sirius satellite radio which, with the help of an adapter from http://rush2112.net attaches to my openbsd system as ucom(4)
so, we chatted some more and i brought up the idea of using 1-Wire temperature sensors remotely. we had already discussed having them in the box itself too, but remotely ... more work possibly? not really, we later determined
the plan is to have a 1U box that has about 48 rj45 ports on it. every 6 or so ports are connected to ucom(4) and a uhub(4) device. these uhub(4) devices are in turn connected to an additional uhub(4) which would then have an external usb port on the box. this port would plug in to any system and 48 ucom(4) devices would then attach. this host server would then be able to remote console into 48 other servers/switches/routers, etc
furthermore, we also plan to allow for putting a small SBC inside the chassis. this is entirely optional. in this case, this SBC (gumstix, pcengines, etc) would have it's own ethernet jack which could be put straight on a network directly attaching the 48 serial ports to the network via ssh, conserver, etc
for cabling, we plan on using regular cat5 cable. cat5 has 4 pair. for serial, we'd need 3.5 pair (7 wires) for comms with handshaking. that leaves 1 wire free. also, of those 7 wires, 1 wire is ground. cat5 is cheap and abundant
to connect to the serial port of a server, a regular rj45<->{db9,db25,etc} converter is all that would be needed. these can be bought cheaply or manufactured too
for the remote 1-Wire, all one would need is the appropriate 1-Wire sensor (DS1820 ~$4/sensor) and a M-F adapter. the chain would then go: cable -> male rj45 -> rj45/{db9,db25,etc} converter -> M-F adapter -> server. embedded in the M-F adapter would be the 1-Wire sensor. the 1-Wire sensor would use the un-used wire in the cat5 for data and share ground with ethernet for power
this keeps costs low, but allows room for features. people who do want remote 1-Wire could build/buy the same cable as those that don't. sort of like ala carte cable tv programming ... you build/buy precisely what you want
this does involve quite a bit of electronics work. we're working on designing the pcb, which we are giving away freely. it's up to you to take it and actually build the device
how you choose to build it depends entirely on you. someone might be willing to build it for you. you may choose to get your PCBs etched professionally, or you may try doing it yourself using a laser printer and some acid. but the idea is that the design for the circuitry will be available
we are designing the circuitry using PCB which is available in $PORTSDIR/cad/pcb. pcb is able to export designs to the 'gerber' format which many pcb houses accept for printing. plus, it's FOSS
presently, we are building a full list of the required electronics to implement this. for now, a very short, general list is: