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Topic: W5100 for $20? (Read 4073 times) previous topic - next topic

tkbyd

Oct 22, 2011, 02:54 pm Last Edit: Oct 22, 2011, 02:55 pm by tkbyd Reason: 1
Am I missing something?

Seems to me that the following...

http://iteadstudio.com/store/index.php?main_page=product_info&cPath=18&products_id=477

... gives you the heart of an ethernet shield?

Yes, you would have to run 6(?) wires between this module and your Arduino
No, no POE
No, no SD card carrier...

But if you just want to do something like an ArduServer2... simple web server with an LED clients can turn on and off, and a report back, via the returned webpage, of light level seen a moment later by phototransistor "looking" at LED (See Arduserve.com), all you need?

(They're also doing a neat little 2.4G xciever for $4 at the moment...
http://iteadstudio.com/store/index.php?main_page=product_info&cPath=7&products_id=53

westfw

If you want to string wires around, you've been able to get w5100 based modules direct from Wiznet for quite a while, for about $20:  http://shop.wiznettechnology.com/Sub_Modules/en/product/product_list.asp?cateid=62

You pay significantly extra for the extra convenience and features (uSD, stackability) of an actual Arduino Ethernet shield.

tkbyd

The Wiznet devices... three to decide between... say...

"3.3V internal operation and 5V tolerant I/Os"

... but I see nothing to indicate that 5v can be used to power the modules.

Also, all of them connect to external units via two DOUBLE rows of pins... hard to accomodate on any breadboard I ever saw.

The http://iteadstudio.com/ device says explicitly that there is an on-board regulation, so you can use 5-12V VCC input. It goes on to confirm that the other pins are happy with either 3.3V or 5V operation level.

===
Obviously, there are certain advantages to dealing with "the source" of the W5100... but the secondary market players can be "hungrier". I couldn't (easily) find a link to datasheet or scematic for the Wiznet units for instance. I was wondering why they "need" 20 pins when the iStore product makes do with 10.

In my ignorance, I prefer the simplified interconnect scheme of the iStore product, and I would like to reward their initiative... but I am not experienced in ethernet interface issues... hence my "what am I missing?" post here!

====
Hmmm... that lead to an "interesting" hour... I finally took a close look at the Ethernet Shield (v5) scehmatic.

If I'm not mistaken, it shows the following in use by the ethernet interface.

Where I say "D10", I am referring to the line which would be affected by the Arduino command "digitalWrite(10,HIGH); (Pin names and numbers will haunt you before you go to far into Arduino hardware!) And An0 is my way of referring to what would be sampled by analogRead(0);

The point of this? Call me a coward, but I'd rather not use these pins/ signals in my software when I am also using an ethernet shield and the ethernet library!

D2
D4
D10
D11
D12
(D13... see below)

An0
An1

(In addition, an LED + resistor is provided with a route to ground from the pin for D13, but this doesn't connect to the ethernet hardware anywhere. So I'd only use D13 as an output to the on-shield LED, or taking that into acount in any other use.)

===
Oh, hell. Wouldn't you know it? When I build my ArduServers and the ArduSimpSrv, I didn't know the shield was using these pins... and I used them to. My devices to seem to work... but more luck than design... and while they have worked for weeks, I'll be more comfortable when I've re-arranged things.

The first ArduServer, the one built around a NuElectronics ENC28J60, may be okay, and it may be using fewer signals.

Sigh. But I guess it wouldn't be "fun" if it were easy!

westfw

#3
Oct 24, 2011, 12:28 am Last Edit: Oct 24, 2011, 03:02 am by westfw Reason: 1
Quote
I was wondering why they "need" 20 pins when the iStore product makes do with 10.

the W5100 chip supports both an SPI (low-pin-count serial) and a higher-speed parallel (lots of pins) interface.  The Wiznet boards allow you to use either one; the itead board supports only the serial interface.


Quote
If I'm not mistaken, it shows the following in use by the ethernet interface.
D2  D4  D10  D11  D12  (D13... see below)  An0  An1

You're somewhat mistaken, I think.  D10 through D13 are all part of the AVR's dedicated SPI interface, and ought to have been used by the ENC28J60 board as well.  D2 is "interrupt" from the ethernet chip, and D4 is a second SPI "chip select" pin for the SD card.  I couldn't find any indication at An0 or An1 was used at all (but I was looking at a v6 schematic.)  Note that the newer Ethernet shields get the SPI signals from the ISP connector rather than the shield connector.  This allows the shield to work with the MEGA, which has its SPI port(s) on different shield pins...
EDIT: the older ethernet shield schematic I have (so old it doesn't have a version number, and a full sized SD card) uses An0 and An1 to connect to the "write protect" and "present" signals of the SD card.  They have 10k pullups, but would be otherwise unconnected if you didn't have an SD card installed.

Wiznet has a new chip, the w5200, that only supports SPI, and is thus smaller and cheaper than the w5100.  It also has more memory and supports 8 simultaneous connections instead of just four.  Simple modules don't seem to have hit the stores yet, but this one looks really sweet:


It's a shame it wasn't out a few months earlier; I bet it would have made the single-board Arduino-Ethernet a lot easier.  (although it would have needed SW/library changes as well.)


tkbyd

Many thanks for the enormously helpful reply!

The new module looks GREAT! And thank you for the warning that a different library will be needed. Come on experts... we can't wait! Get one of these sweet things running!

====
No "question" follows... but if, gentle reader, you want to avoid the trap I fell into...

In particular, thank you for the corrections to my pin use comments. Not to make excuses, but to help others avoid the mistakes I made, here's how I went wrong on one of the points....

When I examined the schematic I have for the Arduino ethernet shield... (ver 5... and PLEASE if you are in a position to influence these things: Put version numbers on PCBs!!)... I saw, at connector "J1" ("IOH" on the Uno diagram), an LED (with resistance) on pin 6, connected to the Atmega pin we use as "D13". Unlike the Uno's schematic, the line was not also labelled "SCK", but I probably wouldn't have thought enough about that anyway.

Elsewhere on the diagram, we have the ICSP connector, with "SCK" on pin3. As I wasn't plugging anything else in there, in this project, I might have discounted that if I'd noticed, and remembered that the Uno diagram tells me that IOH-6 connects to ICSP-3... but that's not all.

In a third place on the diagram, going into RN5B, we have another SCK line... the same one, of course, as appears in other places.

So! Moral of story? If you see "just" an LED on a pin... be careful that the same pin, or something connected to it, doesn't appear elsewhere on the diagram.

Oh joy! A chance to use a phrase I like! "Absence of presence is not proof of absence"!

(Ha! While researching that, I discovered that the same thing applies another way to the connections shown to the ICSP connector... On the Arduino Uno schematic, on first inspection, one sees, for example, pin 1 going to the D12 line, and labelled MISO. Closer inspection reveals a "second" ICSP connector... really just another representation of the one I saw first, and THERE we see FURTHER connections to pin 1 of the ICSP connector. Had I looked at the "second" one first, I would have made a similar mistake, just the other way around. (I would not have realized that ICSP-1 also goes to D12. There are some similarly "cryptic" connections to D0 and D1)

===
Your comments on the other lines also very helpful, thank you.

bubulindo


Many thanks for the enormously helpful reply!

The new module looks GREAT! And thank you for the warning that a different library will be needed. Come on experts... we can't wait! Get one of these sweet things running!

Don't think the changes will be that big...
This... is a hobby.

DCContrarian

The last ethernet shield I bought was $29 including shipping on ebay. It hardly seems worthwhile to mess around to save $9.

kucza83

Quote
The last ethernet shield I bought was $29 including shipping on ebay. It hardly seems worthwhile to mess around to save $9.


Just my words! Look here:

http://www.ebay.com/itm/Arduino-W5100-Ethernet-Shield-support-micro-SD-Card-POE-Mega-1280-2560-00930-/280760520368?pt=LH_DefaultDomain_0&hash=item415ea18eb0

... and you'll get at SD card slot

tkbyd

There's good sense in that suggestion that saving $9 isn't worth it...

But I never resist a "bargain". Sigh. And it DOES help keep prices down if the low bidders get some business once in a while?

Hey! Help! What's this about the Uno not working with the Arduino Ethernet shield? (There was a note to that effect in the eBay listing.)

westfw

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What's this about the Uno not working with the Arduino Ethernet shield?

How is anyone here supposed to know that?  It's some sort of clone, not the current official board.  You'll have to ask the vendor.  Maybe they made a mistake in the cloning process, and are thus getting rid of these boards at the low price...

whisperninan


tkbyd

#11
Oct 25, 2011, 10:16 am Last Edit: Oct 25, 2011, 10:20 am by tkbyd Reason: 1
Quote
How is anyone here supposed to know <why the eBay wonder doesn't work with Uno>?... It's a clone


Oh. You know it is a clone? I was afraid that perhaps the official Ethernet shield- with- POE option didn't work with the Uno. Does anyone know for sure that the official one does, please? (Please, official Arduino people if you are reading this, put proper version IDs on your products and schematics, so we can say unambiguously WHICH boards we are talking about!)

Quote
It's a good deal.


Well... yes... If you aren't wanting to use it with a Uno! Or wanting to do something else that it should do, but doesn't... and who knows what's on that list?

------
Has anyone with a rep here bought one, found it reliable? (I say "with a rep", because I'm not interested in a post from the seller saying, "Oh yes! Of course!") (smile)

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