WiShield 2.0 on Leaf Labs Maple - can it run at 3.3v?

[adamfeuer]

Folks,

I'm thinking of porting the WiShield drivers and the uIP stack to run on the Leaf Labs Maple board (http://leaflabs.com/devices/maple/) - this is an Arm Cortex M3 system that is almost hardware compatible with the Arduino. At least, it shares a similar development environment, can run many sketches unmodified, and shields meant for Arduino can plug into it.

However - the Maple runs at 3.3V. Can the WiShield run at 3.3V?

I looked at the schematic, and the G2100 runs at 3.3v, so that should be ok. The Maple provides 3.3V to the pin marked 5V on the WiShield. Maple also provides 3.3V to the pin marked 3V3. The MCP1700 voltage regulator is connected to the 5V pin. The datasheet seems to imply that the MCP1700 used as a voltage regulator at U3 on the WiShield can take a 3.3V input and produce a 3.3V output.

Is this the case? It seems to be so, but before I spend some hours working to get the software ported, I thought I'd ask here to see if there was something critical I missed!

(Why I'm interested in doing this: I want to build a data acquisition device that can provide about 2000 24bit ADC readings per second via HTTP. I believe Arduino is not capable of this throughput, but the Maple's Arm Cortex-M3 is a 32 bit processor running at 72 Mhz, about 4.5 times the 16Mhz 8 bit AVR processors used on the Arduino, with 20KB ram [20x the AVR] so this seems like it should work.)

If anyone cares to weigh in on this - I would be grateful to know your thoughts.

cheers
adam
--
Adam Feuer
Seattle, WA, USA
[email protected]

[adamfeuer]

Folks,

Also - is there a programming manual for the ZG2100M? I can only find the data sheet on the net. I wanted to write a simple SPI sketch on the Maple to verify that the board is working, and wanted to refer to a reference manual. But I can't find one!

Does anyone know if there is one, and where it's located?

cheers
adam
--
Adam Feuer
Seattle, WA, USA
[email protected]

[GregEigsti]

MicroChip recently bought ZeroG; take a look on the MicroChip site for the data sheets. There is also a MicroChip "network programming sdk/reference" (Windows required) that contains a lot of useful source/headers for the ZeroG. Let me know if you have problems finding any of this good stuff and I'll try to give a hand.

Good luck! Neat project - keep us updated! I have a FEZ Domino and have gone back and forth on doing the same thing for it.
Greg

[adamfeuer]

Greg,

I have looked at the MicroChip site, but couldn't find the manual you cite - will you post a link?

-adam
--
Adam Feuer

[GregEigsti]

http://ww1.microchip.com/downloads/en/d ... taller.zip

Sorry, been slammed.
Greg

[mengineer]

I've been debating the idea of getting a Maple myself, waiting to see the Maple Native out first though. How do you like it so far? I like the idea that it would give me even more power/memory to play with than my mega currently does(Although the 128kb isn't full yet and the data flash on WiShield barely touched) .

[adamfeuer]

I like it fine, and sketches seem to work well. There are some missing libraries, but most things work. But the main reason I bought it is to use it to stream data over HTTP. I don't have the driver and uIP stack working yet so I don't know whether that will work...

I will post here if I get it working.

-adam
--
Adam Feuer

[GregEigsti]

Keep us informed! Maybe you could get a FEZ Domino and we could collab - I'm just over in Sammamish (yeah an East sider).
Domino - nice dev tools and debugging from the computer...

Greg

[3DTOPO]

Hey Adam,

Just got my Maple yesterday. Looks like we are in the same boat.

I don't have really any experience porting hardware drivers, but I have a ton of experience porting software.

Please let me know if there is anything I can do to help.


-jeshua

[mikepo]

Hi Adam,
did you ever figure out the answer to your original question, i.e if the WiShield will work on 3.3V without modifications?

I haven't tried it, but I just looked at the datasheet for the MCP1700 voltage regulator:
http://ww1.microchip.com/downloads/en/DeviceDoc/21826b.pdf

It seems to show that you can expect a typical dropout voltage of approx 75mV @ 100mA (page 6 - not sure how much current the WiShield actually draws).
So if the Maple 3.3V regulator actually puts out >3.375V instead of the nominal 3.3V then it should work, but it's a gamble on component tolerances and not reliable.
So the short answer is: It might work on a case by case basis, depending on the component tolerances.

I think if you decide to use the WiShield exclusively with the Maple or any other 3.3V device, then it would make sense to remove the MCP1700 and put a solder bridge in its place.
Of course then if you plug in that shield into a regular Arduino you'll see some smoke

Let me know if you found out it works or not!

Also, I am following your WiShield porting efforts for the Maple board, that will make the Maple a lot more useful...

Mike