The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Tuesday, January 31, 2006

MacGyver, with the obligatory paper clip

I fixed a communication problem with some scissors, a bit of wire and a paper clip.

No, really.

I got two pieces of equipment communicating by using stuff I was able to find around the office (because that's all I had to work with).

Yesterday, Smirk drops a BayTech DS9 with one DS72 network interface and eight DS30 modules (which control 12 electrical outlets). I was told to test it and configure the device.

So I plug the device into the office network, started up the DHCP server, and powered the DS9. Sure enough, I see the DHCP request come through, it gets an IP address and I try connecting to it.

Nothing.

I scan the device with nmap and yes, it is studiously ignoring all attempts to connect to port TCP port 23 (standard telnet) and UDP port 161 (SNMP). Since it's studiously ignoring the network, my only recourse is to get at it through the serial port.

It's an RJ-45 connector on the DS9, and I have a DE-9 (commonly referred to as DB-9 but DE-9 is the proper designation for the connector) on my workstation. I just so happen to have an RJ-45 to DE-9 adaptor (for the Cisco routers). I may or may not need the NULL modem adaptor, but that's easy enough to figure out.

Only it doesn't work. Straight through, or with the NULL modem adaptor.

I have to reach for the heavy guns. I hunker down and read the manual. It's a good manual, and it gives the exact layout for the cabling between the RJ-45 and the DE-9 that I need to communicate with the DS9. So I go hunting for a continuity tester to see if the Cisco-specific adaptor I have is wired such that I can use it.

Only we don't have a continuity tester. A $5,000 network cable analyzer sure. But something to test the continuity of a single wire? Nada. Not even Dan the Network Engineer has one.

So I carefully break open the Cisco-specific RJ-45 to DE-9 adaptor and lo—it's not wired according to the DS72 manual, so it's useless. So are the other RJ-45 to DE-9 adaptors we have lying around.

So I have to make one.

Only we don't have any spare DE-9 connectors (male or female) lying around, but plenty of RJ-45 connectors. Hmmm …

I grab about a foot length of network cable, crimp an RJ-45 connector on one end, and (carefully) use scisors (since we lacked actual wire strippers) to strip the insulation off the wires at the other end. I then carefully wrapped the exposed wire around a paper clip to make a small coil, and then slipped that coil around the pins of a male-to-male DE-9 adaptor, and plugged that into the serial cable at the back of my workstation. The RJ-45 end of the jury-rigged cable went into the DS9.

The fragile kludge made from scisors, wires and a paper clip (oh, and a crimping tool) worked beautifully and I was able to configure the DS9 (and I kept cursing myself for not having my camera around to document such an engineering feat).

I did find out one thing about the device, and I don't think it's mentioned in the manual (although I was more concerned about the serial connection than anything else) but the device simply drops packets unless they come from a configured SNMP trap host. Good thing to know.

Obligatory Picture

[It's the most wonderful time of the year!]

Obligatory Links

Obligatory Miscellaneous

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