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Mon, 24 Sep 2007
I'm always interested in cheap ways of getting small embedded devices onto an Ethernet network. For some time now the cheapest options seemed to have bottomed out at the USD$40 mark (chip + magnetics + PCB ready to go) or so. Still not quite at the point where you'd sprinkle a dozen around the place and not think twice about it.
An article in this month's Circuit Cellar magazine about the WIZnet devices caught my eye. The chips in question are about USD$4 or you can get various eval boards starting from USD$12 for chip + magnetics + PCB. This is low volume pricing - one to ten pieces!
A quick dig through the data sheet of the part in question (iEthernet W5100) yielded the following;
- SPI and MCU Bus interface options
- Integrated 10/100 Ethernet MAC and PHY
- Inbuilt TCP/IP stack
- Onboard RAM for TX/RX buffers or "Socket" buffers
From an API standpoint you basically get a set of memory addressable registers where you set things like MAC address, IP address, Netmask and Gateway etc. Another part of the register space lets you configure the "Socket" mode where you can set the chip up to run as a TCP Client or Server. When a connection comes in you get an interrupt and take things from there.
On an initial read through they really do seem to have done the heavy lifting so you can read/write bytes from a socket (or UDP) connection as trivially as you would a simple UART.
Have added one of their boards to my "Buy and poke at" list, will write up what I discover once I get started on it. Must admit to a couple of other things needing sorting first tho, so feel free to beat me to it... :)