Home Networking – Mike's Twitter Overflow

Weird Harmonics? A Whistling HP 6830 Printer?

I have a HP 6830 printer.

It is making a high-pitched, barely audible, but just enough to be annoying (to me anyway) whistling/singing noise, that sounds a bit like modem noise.

The frequency and pitch of the noise changes when it’s wifi client is switched off. It’s still there, just slightly different.

The whistling noise is still present even when the printer is in standby.

It changes pitch again when it is powered down.

It goes completely once the mains lead is removed, and returns when the mains lead is plugged back in.

Sadly, I’ve tried recording it, but nothing I’ve got seems to be able to pick it up clearly.

Anyone else got one and come across this?

When parents-in-law move homes – a tale of being “default” tech support

Sheesh BT.

The MiL has moved. Around the corner from her old house. She had BT Infinity (BT’s Retail FTTC product) at the old house. She ordered the service to be moved. The voice service was activated on the day she moved, but not the Internet access.

The new house has previously had FTTC with the last occupant, it has the FTTC faceplate. One can only assume that the “double jumpering” to the FTTC MSAN is still in place too.

I wouldn’t mind betting that it’s even coming off the same bloody street cab/MSAN.

Can we just take the old Homehub 3 and VDSL modem over and plug those in? Oh no.

BT have sent a new Homehub 5 and scheduled an engineer visit for Friday, 5 days after she’s moved in.

It just feels a bit wrong, and maybe even on the crazy side. In theory this could have been done as a simultaneous provide – i.e. both the voice and the internet service brought up at the same time, and in this case potentially without an engineer visit!

Who knows why it’s not happened. Certainly the MiL wouldn’t have known to ask for a “sim-provide”, but should she have to?

Getting info out of your HomePlug AV Network

I recently blogged on the trials and tribulations (and gotchas) of using HomePlug AV to glue bits of network together around the house without having to run UTP around the place.

One of the comments I’d made in that article was about monitoring and logging the node-to-node speeds between the HomePlug bridges. Obviously, being a consumer product, they come with a pretty (and depending on your PoV, awful) GUI.

How was the information being gathered by the GUI? Turns out it’s using a Layer 2 protocol, so I cracked out Wireshark.

The head and tail of it is that the requesting station sends a L2 broadcast frame of ethertype 0x88e1 (Homeplug AV), containing a network info request.

The HomePlug bridges reply to the MAC address originating the broadcast with a network info confirmation – there are other sorts of management frames (such as read module data and get device/sw version), but this is the bit we’re interested in, containing the negotiated speed between each pair of bridges.

The speeds are plain hex values, which occur in certain places in the frame.

The number of networks (and therefore how many instances of “Networks informations“) to expect are in byte 21 of the frame, and the number of AV stations in a network is embedded in byte 17 of the Networks Informations, so you then know how many sets of stations informations to expect.

In the stations informations the address of the far end HomePlug bridge is in the first 6 bytes, while the TX rate is in byte 14, and the RX in byte 15.

It should therefore, maybe with a bit of scripting, be possible to grab those values and write them into a rrd or something like that, and make graphs, rather than have to fire up a GUI which only helps you in realtime. But here I am talking about banging away with my awful scripting crafting specific L2 frames and interpreting what comes back using regex matching and chomp. Surely someone’s done something like this before, and come up with something more elegant?

Well it turns out, github is your friend, as it seems are the people at Qualcomm Atheros who make the chips inside a lot of the HomePlug devices.

They’ve put up something called Open Powerline Utils – which I think may be able to do the job I want.

So, when I get a free evening, I’ll have a read of the docs and see what can be boshed together using this toolset rather than some ugly scripts.