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August 22, 2011
News - Enginursday: Monitor Twit… |
about 5 months ago
Of course, you must choice wathever languaje fit better in your proyect. But it’s always good to have options.
In my case, I use C for a fast embeded project, but i will use C++ for a more robust project. In a PC enviroment, I preffer C# / VB.NET.
In the web world, I preffer ruby, but most of my previous proyects were PHP based.
In the arduino.cc/yun forum, many of the topic are php / sqlite related. There a lot of PHP fans out there…
The arduino yün also support python on the linux side. You can also install php on it.
News - New Product Friday: The p… |
about a year ago
In the part 2 of the Shieldstravaganza, Robert talk about the ethernet shields. The first one (at 0:55) is the Sparfun PoEthernet shield. (DEV-10864). The second one (at 5:20) is the oficial Arduno Shield with de PoE Module. (DEV-11230).
The Sparksfun shield uses pasive “unoficial” PoE, inyecting power over the 7,8 (+) and the 4,5 (-) pins. You still need a PoE inyector and a power source to put the power in the ethernet cable.
The Arduino shield uses the “standart” IEEE 802.3af. This way, uses a PoE source (mainly ethernet switch) to put the power in the cable. This schema modulates the data using the same cables used to the PoE. In gigabit ethernet, all 4 pairs are used, and still is posible to use “official” PoE.
Those two ways to build a PoE circuit are compleatly diferent, and not compatible.
News - Engineering Roundtable - … |
about a year ago
I’ve been developing sketches for the arduino Ethernet shield for some time. I must you can improve the code putting the html to the program memory, not just as string, because the RAM requirements are much greater. In my projects I prefer to store the HTML in the SD card of the Ethernet shield. (I know, the wifly shield does not have one)
Other point is about security. I think is important to put some way to only allow to enter to your system only the authorized people. Have you ever use a port scanner? It’s easy.
In your code, the comments on line 200, says that you put some code to put a reload button and it breaks everything. How long is the actual HTML output? You always must think about TCP fragmentation, were a TCP packet must be 1500 bytes or less, including headers. If the whole HTML does not fit on a single packet, it will split in two or more packets. That’s called fragmentation. In your code, you must keep an eye in this problem, because the (at least in the Ethernet shield) communication IC does not handle the fragmentation by itself. It just send the packets one after another, without the packet number.
The packet number is needed by the client to put all the received packets in order, (TCP/Ip does not guarantees the ideal packet route, so the packets can travel using different routes, taking different times and finally arriving in different order) and then passing the data to the browser.
I strongly recommend to use a TCP/IP sniffer to see the actual traffic going from the server (the arduino + Wifly) to the browser in order to debug.
You can reduce the fragmentation programing with AJAX, in order to feed only xml/json files to the browser from the arduino, and hosting the app itself (HTML, .js, css, img) in other web server.
No public wish lists :(