Aug 18

BT HomeHub 5 has issues with mDNS/Bonjour

I recently upgraded from the BT HomeHub 3 to their latest offering, the BT Home Hub 5.

However immediately on replacing the old router with the new one I started having problems with my networked printers. I have a pair of HP OfficeJet 7500A printers, attached to my home network. Once I had upgraded to the Home Hub 5, I could see the printers on the network, but I could not print to them.

To cut a long story short, I did a bit of digging about with Wireshark and Bonjour Browser and discovered the issue. The printers advertise themselves on the network using mDNS (also known as Bonjour in Apple circles). With mDNS when a computer wishes to find a provider of a certain service, such as printing, it sends out a service discovery packet on the network, and all the devices which provide that service reply with their details. This is known as ‘service discovery.’ In the case of these printers the service is known as “_ipp.tcp” (Internet Printing Protocol).

The problem that I’ve been seeing with the HH5 is that this service request and discovery process does not work for certain devices – but only when the computer issues the request via the HH5’s LAN interface (ie, the wired ethernet ports). If the computer is connected to the home hub using WiFi then the service discovery process works properly.

mDNS and Bonjour work by sending the service discovery packets to a well known ‘multicast’ address: 224.0.0.251 – It looks to me like the HH5 is not passing these requests on the LAN interface correctly. Yet it does work on the WiFi interface.

It could be the size of the TXT record that is at the heart of the problem, because these printers return quite a large TXT packet, but I have not been able to verify that. Even so, it works fine over the WiFi interface, so it should work on the LAN interface.

Finally, if I go back to using my old BT Home Hub 3, then it all works fine on both the LAN and the WiFi interfaces, leading me to deduce that there is an issue with mDNS/Bonjour being used with HH5.

I’ve contacted BT and sent them packet captures and all kinds of data, but they don’t respond. It would appear as through they simply do not care about this issue.

Aug 15

Galileo GPIO Timing & why it doesn’t work for some.

The Intel Galileo is has Arduino UNO compatibility, yet often I see queries from someone asking why their favourite Arduino Shield won’t work, or why an interface they have made which works on other Arduino boards, doesn’t work with Galileo. Often they say Galileo is no use, or Galileo doesn’t do what it claims, or Galileo is slow. So why do some Sketches and Shields not work as expected, when using GPIO on Galileo? Read on for the answers…

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BBC News – Robots inspired by origami fold themselves into action

Aside

Self unfolding robots. Just add heat…

BBC News – Robots inspired by origami fold themselves into action.

Jul 25

The skies are busy

While traveling by air yesterday, it got me wondering how busy our skies are. The answer might surprise you. The following image shows actual flights in progress over Europe at 13:10 BST today. (Click image for a larger view).

Flights Over EuropeAccording to data from FlightRadar24 there were 8830 Flights in progress over world, 2920 of them over europe. This only includes flights on which there was data available, the real figure may even be slightly higher.

 

Jul 02

Dallas 1-Wire iButton teardown.

Recently I’ve been investigating 1-wire iButtons and interfacing them to different systems. I thought it might be interesting to see what’s inside an iButton. So here is my Dallas DS1990A iButton teardown.

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Jul 02

Intel Galileo 2nd Generation board – first pics.

Here is a picture of the new Generation 2 Intel Galileo board.

This pic was taken from the Galileo Getting Started Guide available here.

Click the image for a larger view.

Screen Shot 2014-07-02 at 10.24.27

Jul 01

Intel® Galileo Gen2 Product Brief

Some details are staring to emerge about the new generation of Intel Galileo boards.

Follow this link : Intel® Galileo Gen2 Product Brief | Intel Communities.

Jun 17

iPhone self destructs with bulging battery.

My iPhone 4 has dangerously self destructed, with an unexplained bulging of the battery which broke off the rear cover and cracked the front display.  Continue reading

Jun 16

Reading 1-Wire iButtons using Cypress PSoC 3 and 5/5LP

Previously I posted about using a standard UART to read and write to 1-Wire devices. In this post I look at how to read and write to these devices using Cypress PSoC devices. Continue reading