====== Descritption ======
Ethernet m0dul. Makes the r0ket speak IP. Currently in planning.

====== Idea ======
Main reason to do this is to get the received Openbeacon data from the r0ket to a central location in a nice and easy way.

===== Alternate Options =====
There are of course other options to do this:

We currently get the data off via USB-Serial, this requires one USB port per r0ket -- due to the length limits of USB cables about one Computer (Dockstar/etc.) per 2 r0kets. This requires more Hardware and more configuration for roughly the same effect.

We could get the data off via rf - i.e. Wlan or Xbee.

  * Long-Range Xbee is rather expensive, we currently have no receivers and no deep knowledge of it.
  * Wifi: Own Wlan would clash in crowded locations and might not reach far enough. Normal Participant wlan is possibly not stable enough. Also: running Wlan from r0ket sounds complicated unless there are all-in-one chips.

====== Hardware ======
Plans on how to do it on the hardware side.

===== Ethernet Chip =====
Two main options.

Use a "simple"/"stupid" Ethernet chip, and do IP in the r0ket.
  * Pro: cheaper, cool, we can tweak it, we know exactly what it does.
  * Con: limited space means we will probably only get UDP, and maybe DHCP. Enough for our logging stuff, but difficult for other projects, only 10baseT
  * [[https://secure.reichelt.de/USB-CAN-BUS-Controller/ENC-28J60-I-SP/index.html?;ACTION=3;LA=444;GROUP=A316;GROUPID=2946;ARTICLE=89340;START=0;SORT=artnr;OFFSET=16|ENC28J60]] 2,60€ - 2,95€ bei Reichelt
    * Please do not use this chip. It's a pain to work with, doesn't do Autonegotiation, loses packets and has weird unfixed erratas. --equinox
  * [[http://www.micrel.com/_PDF/Ethernet/datasheets/ksz8851snl_ds.pdf|Micrel KSZ8851SNL]] [[http://de.futureelectronics.com/de/technologies/semiconductors/comm-products/switch/Seiten/3385572-KSZ8851SNL%20TR.aspx?IM=0|part source: Future Electronics]]
    * considerably simpler buffer/queue management than the ENC28J60
    * supports 100base-TX & Autonegotiation
    * supports Auto-MDIX (Crossover)
    * QFN32 package
    * ca. 3€

Use a "smart" Ethernet chip which has a full TCP/IP implementation.
  * Pro: can do other cool stuff, supports 100baseT
  * Con: more expensive, possibly bugs in the IP stack. No IPv6.
  * [[http://de.mouser.com/ProductDetail/WIZnet/W5100/?qs=b%252bXOOdUOuvYgHyLQGbrIO23GrGQAD4og|W5100]] 4,03€ bei Mouser

-> So far it looks like the "smart" variant is the way to go.

===== Power =====
It would be nice to be able to (optionally) power this via [[https://en.wikipedia.org/wiki/Power_over_Ethernet|POE]].

Again two options here:

  * "simple" homegrown POE (just use the unused pairs to send Power)
    * **homegrown/uncontrolled PoE will be instantly refused by the NOC.**  Frying an 20k€ Switch by misplugging a cable is not an acceptable risk.  This applies for all uses that touch the building infrastructure -- even if it's not supposed to be linked to a "big" switch you can always misplug something.
  * "normal" POE (802.3af or 802.3at) (.af sounds simple - provides for ~ 200mA @ 48V - enough for us)

according to Wikipedia, the injector decides wether to provide power via the "unused" or the "data" wires, which means more work for us...

-> Still undecided.

===== RJ45 Connector =====
 
As far as I can tell, we **must** decouple the ethernet lines from our ciruit. Doing this sounds like no fun[tm].

There are RJ45 Connectors with "integrated magnectics" which do this for us. But they then need to be POE-Capable which appears to be quite expensive.

1-6605834-1 is 6,08€ at mouser (http://www.te.com/catalog/pn/en/1-6605834-1)

"simple" RJ45 Connectors appear to be at about 0,90€ 

-> Still unclear if there are no other options.

Discrete Magnetics:
  * [[http://www.epcos.com/inf/30/ds/lan_mod/B78476A8245A003.pdf|Epcos B78476A8245A3]] [[http://de.futureelectronics.com/de/technologies/passives/transformers/signal-magnetic-transformers/lan/Seiten/5173968-B78476A8245A3.aspx?IM=0|source: Future Electronics]] 100MBit PoE

Recommended reading for magnetics selection: http://www.ceetus.com.cn/paper/VSC8201.pdf (Vitesse magnetics design note, cannot find original on Vitesse's website anymore)

===== Connection to r0ket =====

Over m0dulbus. All the Ethernet chips above do SPI.

====== Software ======
Nothing done yet. Need to decide on the Hardware first

Please implement [[http://en.wikipedia.org/wiki/Link_Layer_Discovery_Protocol|LLDP]] and you will make the NOC happy :)
(Possible on all of the chips, simple ethernet protocol.)

===== Openbeacon Reader =====
The openbeacon reader protocol we want to emulate is fairly known.
Check [[tracking]] or [[tracking:reader]] for more details.