Ethernet Shield With PoE
Freetronics's Description of the Ethernet Shield With PoE
Put your Arduino online with the Freetronics Ethernet Shield and have it talk to the world. Do Twitter updates automatically, serve web pages, connect to web services, display sensor data online, and control devices using a web browser. The Freetronics Ethernet Shield is based on the same Wiznet W5100 chip used by the official Arduino Ethernet Shield, and is 100% compatible with the Ethernet library and sketches.
However, we've made a few little improvements of our own.
The big news is PoE (Power-over-Ethernet) support, which means that at last you can plug your Arduino into an Ethernet network and have it fire up right away with no direct power connection. Brilliant! But it gets even better. We've brought the PoE connections out to a header on the shield, which gives you the flexibility to use it in different ways to suit your own requirements:
1. Put a couple of jumpers across the headers and feed about 12Vdc down the Ethernet cable for a dirt-cheap DIY solution. Perfect for use with our 4-Port PoE Midspan Injector.
2. Fit a low-cost PoE Voltage Regulator 24V daughterboard that plugs in and lets you feed up to 24Vdc down the Ethernet cable. Compatible with many low-voltage commercial PoE systems and third-party midspan injectors, including our own 4-Port PoE Midspan Injector.
3. Fit a PoE Voltage Regulator 802.3af daughterboard that negotiates a connection with commercial 48V PoE switches and allows you to run your Arduino and Ethernet Shield on full-power PoE networks.
You can read more about PoE in our tutorial at Power-over-Ethernet For Arduino.
What's the point of connecting your Arduino to a network and not having any space to put on other parts, such as sensor connections or control outputs?
So we crammed all the Ethernet circuitry up to one end of the shield, leaving fully half the shield available as a general-purpose prototyping area. Now you don't have to stack a prototyping shield on top of an Ethernet shield!
Combining Ethernet with other SPI devices can be really tricky because the Wiznet chip doesn't relinquish the bus properly when it's deselected. To fix that problem we slaved the Wiznet's SEN (SPI Enable) line to the CS (Chip Select) line, which means that whenever your sketch deselects the Ethernet connection in order to talk to another SPI device it will work exactly the way it should.
No more messing around with cutting tracks and other nasty hacks you may have seen mentioned on the forums.
We've also slaved the Ethernet Shield's reset line to the Arduino reset line, so if your Arduino is reset the Ethernet Shield will automatically reset as well. The Wiznet reset line is also held active for long enough to make it restart reliably each time the Arduino itself restarts.
Power Filtering Fixes
Ethernet connections are very susceptible to electrical noise, so the Wiznet chip has multiple ground pins on two separate buses and they need to be individually decoupled and the buses linked by an inductor. We took care of that by implementing proper decoupling on the power and ground rails, ensuring you get maximum reliability even in electrically noisy environments.
But that's not all. Other features of the Freetronics Ethernet Shield include:
- Auto-sensing 10/100base-T connection.
- Gold plated PCB.
- Connection overlay on both the top and the bottom so it's easy to see what you're connecting.
- All Arduino headers brought out beside the prototyping area for maximum convenience.
- LED status indicators for TX, RX, collision, duplex, 10/100, and link.
- Stackable headers so you can put another shield on top.
- Sexy rounded corners.