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211  Using Arduino / Networking, Protocols, and Devices / Re: Suggestion for a WiFi system on: September 23, 2012, 03:45:13 pm
And that has to be WiFi or just wireless ?
If it can be " just" wireless then that opens up a whole lot of options that are potentially much less expensive than WiFi. Xbee rf is a lot less costly and there are a lot of projects using it successfully for such things as remote controlled " something".

Now, if you want to remote controll something wirelessly through an iPhone or iPad that will definitely make things more expensive as the wireless options a rather limited to WiFi and Bluetooth. And Bluetooth seems to only work if you jailbreak the device and run BTstack.

How about this for example:

http://www.element14.com/community/videos/1910/l/tutorial-09-for-arduino-wireless-communication
212  Using Arduino / Networking, Protocols, and Devices / Re: Suggestion for a WiFi system on: September 23, 2012, 01:33:10 pm
If you could provide a description what you want to achieve with your project it would be much easier to answer if the solution I suggested is " easy"
It was easy in the case of my project. I wanted to be able to remotely controll a rather sophisticated RGB Lighting System from an iPhone. There were a couple of Arduino libraries that made this easy. One of them is the DHCP/Bonjour library. In my case the router is set up in " client" mode or perhaps a better description is " bridge" mode. When it connects to my home network the DHCP client on the Arduino (well..an Teensy++ with a WIZ 812 Ethernet Module) receives an IP address from my AirPort Extreme router. Then the Bonjour service on the Arduino registers a service  (OSC through e ArdOSC librar) on the network. TouchOSC on my iPhone picks it up and I can connect very quickly to the lighting system in true ZeroConf fashion. Easy!

Your project may do something entirely different. Perhaps you can describe what you want to do.
213  Using Arduino / Networking, Protocols, and Devices / Re: I2C Distance on: September 23, 2012, 01:17:01 pm
I don't disagree with your assessment. Very educational!

The technical documentation I have provided links to provides very detailed instructions on how to overcome problems such as yours.

The Arduiuno drives the I2C bus with 5V. Given the resistance and capacitance of 200m of CAT5 Ethernet cable you can obviously approach the problem in different ways. Reducing the bus frequency is one, however, at a substantial loss of data rate.
If you want to maintain a higher data rate, the other approach is to drive the bus at a higher voltage, which in case of an Arduino requires additional hardware. For example a PCA9600 that is able to deal with the higher overall capacitance - as it is specifically designed to worh with twisted pair cable - and the higher line resistance by being able to operate up to 15V.

214  Using Arduino / Networking, Protocols, and Devices / Re: Suggestion for a WiFi system on: September 23, 2012, 12:50:43 pm
If its not a mobile system, why not go with a " standard" Ethernet shield and a little WiFi pocket router like the TP- Link TP WR702n ?
Heck, even if its a mobile system this would work.
215  Using Arduino / Networking, Protocols, and Devices / Re: Need a wifi shield. on: September 21, 2012, 05:44:05 pm
Sorry, I guess I left that little detail out   smiley-grin Yes, the 702 has an English web interface.

As I said, the 703 router comes in AP mode. If you want to integrate it into your home network as shown in your little " sketch" then it is easiest to switch it into "bridge" mode. So Google Translate is your friend.

I'll see if I can find the file I generated with open office where I wrote down part of the menu structure  that I translated with Google Translate. If I find it I'll post it here. After all for the price of the 703 - I think I paid $26 for it on eBay - it's a nice piece of equipment and this MIT be useful to someone ;-)
216  Using Arduino / Networking, Protocols, and Devices / Re: Wifi shield for mini on: September 21, 2012, 11:39:22 am
What Pylon said!

Unless you have a WiFi shiled already I'd go with this:

http://www.saelig.com/BRD/BRD032.htm

connected to that:

http://www.tp-link.com/en/products/details/?categoryid=241&model=TL-WR702N

Not much bigger (if any at all) and possibly less expensive. Most WiFi shield are pretty darned expensive and thjis solution will also enable you to use the Ethernet library as is and other Libraries that are based the Ethernet Library.
217  Using Arduino / Networking, Protocols, and Devices / Re: Need a wifi shield. on: September 21, 2012, 11:32:54 am
I actually have both, a WR703n and WR702n. You are correct, the 703 interface is entirely in Chinese. I copied/pasted the chinese symbols into Google Translate and made it through. However, if you want to play aroud with settings a little more often then I would get the 702. the 702 does not have the 3G modem ability of the 703 and also uses different electronics, so you will not be able to reflash the 702 with a OPenWrt image https://openwrt.org/ and the different hardware is also the reason that you cannot just flash a 703 firmware (available on the TP-Link website) onto a 702.

I agree that using a web interface to comfortably configure the router is something - to my knowlede - no WiFi shield offers, which I find very valuable, particularly if other, less technically inclied people need to interface with a project/device.

The 703 came pre-configured as an AP with DHCP enabled. My project uses the DHCP/Bonjour library and using this router pretty much made it a plug and play solution.

The 702 came pre-configured as an AP as well but oddly enough with DHCP disabled which I changed.


Both units can be configured in client mode which is very similar to bridge mode and makes it very easy to integrate them into an existing network.
218  Using Arduino / Networking, Protocols, and Devices / Re: attempt at SMS from arduino on: September 20, 2012, 11:21:44 am
There are also Arduino alternatives like the Teensy and Teensy++ boards that offer USB host mode "out of the box" without the need for an additional shield. I case of the Teensy++ thay are cheaper, much smaller, with more flash and ram memory and firmware uploads are at full USB speed and lightning fast.

http://www.pjrc.com/teensy/td_libs_USBHostShield.html

219  Using Arduino / Networking, Protocols, and Devices / Re: new I2C library? on: September 19, 2012, 11:16:11 am
Not sure if this is the one ou are referring to bot her goes:

http://dsscircuits.com/articles/arduino-i2c-master-library.html

Works nicely!
220  Using Arduino / Networking, Protocols, and Devices / Re: I2C Distance on: September 18, 2012, 05:53:02 am
Granted, thar may work but obviously at a very substantial loss of data rate. A PCA9600d costs $2.08 at mouser and is hardly an investment and provides you with a rock solid solution.

You experimental way, however, has something defiant. I like it ;-)
221  Using Arduino / Networking, Protocols, and Devices / Re: Accessing ethernet Arduino on LAN from internet? on: September 18, 2012, 05:34:07 am
You need a bit more than just port forwarding ;-)

1. In order to be able to connect tou your home network you need to know what it's public IP address is. Your Internet service provider likely a has assigned a public, dynamic IP address via DHCP to you, so each time your router disconnects and then reconnects you may have a different IP address. So yo can either talk to your ISP and ask for a static IP address, which is likely to cost you more money, or you can remedy that by registering at dyndns.com, or no-ip.org. Then you have a name associated with your dynamic 4-byte IP address, for example myArduino.no- ip.org, that you can use instead of the 4-byte IP address.

2. Likely your home network assigns a private, dynamic IP address also via DHCP to the devices in your home, including your Ethernet, or WiFi enabled Arduino. It depends a little on your routers abilities, but, yes, you could port- forward port 80 (http) to your Arduino borards IP. Some routers can do this per device name so regardless of what private, dynamic IP address they have assigend to the device it goes to the right device. Or you can reserve a static IP  address in your Router for your Arduino.
222  Using Arduino / Networking, Protocols, and Devices / Re: I2C Distance on: September 17, 2012, 05:51:45 pm
Of course the hardware is where the problem is, because one those length of cable your signal degrades considerably!
The internal pull-up resistors are less than ideally dimensioned for I2C bus operation. Right the first measurement in this article explains that:
http://dsscircuits.com/articles/effects-of-varying-i2c-pull-up-resistors.html

Then you are using CAT5 cable with a nominal capacitance of 50pf/m. The I2C bus capacitance is supposed to not exceed 400pf and that does not only refer to the cable but the entire system. Past 5m of cable length your system capacitance will degrade your signal to a point where the I2C bus simply will not function reliably. Lowering the operation frequency of the I2C bus will only remedy that to a degree.

In the app note I linked to above (here it is again : http://ics.nxp.com/support/documents/interface/pdf/an444.pdf) they tested several different cables that have a significantly lower nominal capacitance than CAT5 cable. They specifically did not use twisted pair as the I2C signal is bidirectional/unbalanced.

If you really need to go in the range of 200m with CAT5 cable (or even "just" 50) you should use e.g a PCAA9600, which is specifically designed to separate the bidirectional I2C-bus signals into unidirectional TX and RX signals and enables the SDA and SCL signals to be transmitted via balanced transmission lines.

Perhaps you start using an oscilloscope so you have positive verification that your design works ;-)
223  Using Arduino / Networking, Protocols, and Devices / Re: Need a wifi shield. on: September 16, 2012, 10:03:09 pm
Sorry, no, i did not mean to suggest that using WiFi is to per se harder that much than " just" Ethernet, even though to do have to deal with a few more parameters to configure.

I my case I intended to use existing libraries ArdOSC, DHCP/Bonjour that relied on lower level functions in the Ethernet library that directly talk to the Wiznet W5100 chip on the Ethernet shield. Replacing that with a WiFi shield tha tobviously uses differnt ethernet hardware would have caused much more problems than it would have solved!

It really depends on what exactly you want to do. For a mobile application you may be interested in the WiFi shields available at http://www.diysandbox.com. More up- to- date hardware than for example the cutedigi copperhead shield and possibly better support. They seem to be still developing new hardware. Some of their offerings seem to be temporarily out of stock, however.
224  Using Arduino / Networking, Protocols, and Devices / Re: Need a wifi shield. on: September 16, 2012, 07:06:17 pm
I personally would not recommend this shield. It's a clone of the Asynclabs WiShield. While the libraries are still available through the Asynclabs website there is no support and no development going on.
If a WiFi shield is easy to use depends on what kind of project is going to be implemented.

I believe until the official Arduino WiFi shield is a little more mature in terms of hardware but particularly software it will be more of a hackers item and won't be that easy to use.
If your project is not mobile - but even in that case the following can work - you can simply use a standard Ethehrnet shield and connect (via Ethernet Cable) a little pocket WiFi router to it. I've used a TP-Link TL-WR703n and a TP-Link TL-WR702n and this works very well. It's not more expensive than a WiFi shield and you can use the full functionality of the mature Ethernet library and also use many libraries that depend on the Ethernet library and that would not work with a given WiFi shield without considerable work on the library itself..
225  Using Arduino / Networking, Protocols, and Devices / Re: I2C Distance on: September 16, 2012, 06:49:49 pm
Tested connection via CAT5 2 pairs over 200 meters.
No external parts but wires (used internal pullups).
Works almost nice, just set SCL speed to 500hz.
I'm going to add just capacitors to remove SCL spikes from SDA signal but during test I ran into one problem.
In some circumstances, I2C get stuck. I'm using standard Wire library.
Code hangs in twi_readFrom() function waiting for TWI_MRX changed value.
I tried another custom I2C library (by Wayne Truchsess), hangs anyway.
I met the same problem year ago and as I see there is no library guaranteeing 100% stable work.
I don't mean 100%  clear data via I2C, I mean not hanging code even when there is error in I2C transmission.


Before you start arbitrarily adding components like capacitors I'd suggest you start reading some background info on I2C. As you've already downloaded Wayne's I2C library, perhaps you found the info on the same website referring to the dimensioning of Pullup resistors ?

http://dsscircuits.com/articles/effects-of-varying-i2c-pull-up-resistors.html

From your description it appears that the I2C bus simply locks up. I've had the same problem in one of my projects (10 devices over about 5 meters). Wayne's library allows to set a timeout value after which the I2C bus is restarted/reset, which is something the standard Arduino TwoWire library does not offer. If the data you are transferring is not critical that may help your situation. However, that limits the effects but does nothing to deal with the root cause of the problem, which is likely system capacitance and noise. The Application Note I linked to in my post above contains some valuable information that does not only apply when using the I2C bus extenders ;-)
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