I am designing an Ethernet shield based on the ENC28J60 3.3V chip. It will be very similar to Nuelectronics' EtherShield, but with through-hole components instead of surface mounted ones.
I am a total beginner in this field; the logic part of electronics I know, but I have no knowledge or experience with the electrics (is that a word) (EMI, noise, heat and other stuff like that) so all tips are appreciated!
I have some specific questions:
ATM I am using Arduino's 3V3 pin as power source for the ENC28J60 and it seems to be working alright with my breadboard wired circuit, but I have only tested with USB power. (I also doesn't have a multimeter to measure voltage and current levels.) Nuelectronics design uses a separate power regulator to convert Arduino's 5V to 3.3V and I am wondering if that might be a better solution. In the latter case: should the regulator get its power from the 5V or Vin pin?
Right now I have merely connected the ENC28J60's reset input to Arduino's reset pin and it works in my test circuit. But is it the way you are supposed to do it?
Should I have a power (3.3V) plane to complement the ground plane (on opposite sides) or is it better with two ground planes (one on each side)?
I have understood that there should be a capacitor connecting power and ground to reduce noise from the components, but how do I calculate the correct value? Nuelectronics design uses four 100nF capacitors in parallell between 3.3V and ground which I don't understand.
If there is anything else I have forgotten or done in a strange way, feel free to point it out!
Well, I don't think it is possible, as there will always be paths that cross each other OTOH I don't have business as a goal with this, atleast not in the nearest future
I don't see the double-sided-ness as a problem though, as i intend to order it from a company in Sweden which offer to make custom PCB:s even in small quantities.
I would be interested on how this turns out. I have a breadboard compatable board using the ENC28J60 called the PropNIC found at http://ucontroller.com/documentation/PropNICDoc.html. It's made for another controller, Parallax's Propeller, but should work with the Arduino.
Brian_Little: Interesting! I will look to see if I can use it to improve my shield. When I am happy with it (or before that) I will probably publish the source files here under some CC license.
westfw: Well, maybe I just haven't tried hard enough to only use one side
TchnclFl: What do you mean by "only a few jumpers on the opposite side", using jumpers as a way to avoid using the other side of the PCB?
Actually, the way the arduino single sided (the original is the one I did) it's really easy to do two sided etching at home. Use toner resist on the main side, drill small via holes for reference, then use a resist pen (i like a paint pen) for the "jumper" traces. Etch as usual, solder Z-wires into the via holes, and you've got a double sided board.
I've used the technique on other stuff - just make sure the traces on the "other" side are straight lines, and make 'em all parallel if you can. Drill pin-holes for reference with those otherwise useless #80 bits in the harbor freight set, connect the dots with the paint pen.
OTOH I don't have business as a goal with this, atleast not in the nearest future 