I'm working on an Arduino clone that will have an embedded Ethernet interface. I'm basing it on the ENC28J60 chip since it seems like the simplest approach.
The datasheet is here:
It calls for a ferrite bead to reduce EMI. No details are given on value or specifications other than "Ferrite Bead should be rated for at least 80 mA." Having never designed an Ethernet interface before, I'm at a loss.
Looking at commercial designs from Seeedstudio and Nuelectronics (i.e. here: http://www.nuelectronics.com/download/projects/Ethernet_v1_0.pdf ), again, no values are given. Seeed provides EAGLE files of their design, and it's an SMT part in an 0805 package but that's the only info given.
Am I to gather that value doesn't matter at all? How do I select an appropriate part?
Before you go too far with the ENC28J60, have a look at the Wiznet 5100 chips (that the main arduino ethernet boards use).
They are MUCH easier to work with, as they have the TCP/IP Stack etc built in, and it saves a lot of code on the arduino, which in turn gives you more space for your code.
They aren't expensive, around the same price as the ENC28J60. The only downside is that they are 80 pin, which makes them a bit harder to work with when developing compared to the ENC28J60 DIL package. It's worth the extra hassle though, and they can be controlled using SPI so they only tie up a few of the Arduino's pins.
I'm working on an Arduino clone that will have an embedded Ethernet interface. I'm basing it on the ENC28J60 chip
Me too, sort of. I don't like not having a modifiable TCP/IP stack. In a sense the Wiznet is the ultimate in "closed source." But the amount of code inside the Wiznet is probably larger than will even FIT in an Arduino, so the tradeoffs are interesting...
Have you thought about ENC28J60--AVR--AVR (two avrs), with the first running some network code, and the second running the user's sketch? (essentially, make a user-programmable equiv of the Wiznet using ENC and an extra AVR.) In theory, an added advantage could be upload-over-ethernet via a 2nd IP address or special port, connected to the Arduino-AVR serial port...
Have you thought about ENC28J60--AVR--AVR (two avrs), with the first running some network code, and the second running the user's sketch
Essentially, that's what I'm doing. :lol: My design has two AVRs on it - one as an "embedded" processor to handle things the users will always want to do, and one as an "Arduino compatible" to allow sketch upload, shield compatibility, etc.
That said I'm interested to know more about relative code sizes required since I've got a lot of other "stuff" going on. I picked the ENC chip because it struck me as cheap and simple. I found an example sketch (probably from one of the vendors I mentioned above) that was around 4k, which struck me as reasonable. It was a sketch that just serves a simple webpage.
I want some flexibility in my design for other users' plans but ultimately my own plans revolve around using the Ethernet interface for sending alarms to a twitter account and/or email address - so if people can comment on the difficulty (in terms of code size) for those sorts of uses between the ENC and the Wiznet chip I'd appreciate it.
One other "deciding" factor - I only see the W5100 chip in an 80 pin LQFP. That's never gonna fly with this design, which is supposed to be "beginner friendly" from an assembly perspective. I see that there are breakout modules for the chip, but they're big and expensive.