My original project plan called for WiFi connectivity with an AsyncLabs YellowJacket or BlackWidow. But as they were unavailable, I bought an Ethernet shield. Then AsyncLabs announced that they were shutting down, and all my preferred WiFi solutions were no longer available. So I now have the thing working on Ethernet, and I see that LinkSprite is now offering a product (CuHead) that they claim is compatible with the AsyncLabs shield software. My questions are:

1. What have people's experiences with the CuHead been? Good, bad, otherwise? Is it completely compatible?
2. How much work is it to go from Ethernet to WiFi?

I can't answer 1 directly, but if you are open to using other solutions, you can just get a WR703N TP-Link wifi mini router (for around $20)  and connect to your ethernet shield. Using this solution, the answer to question 2 is 0 work.

I heard about people solder some wires directly to a microSD Adapter and use this as an interface to microSD cards. 

Ah! I should have thought of that. I have a few of those adapters laying around, I'll try to wire them up. The SD card contacts are essentially the SPI pins. The genius is in the simplicity of the solution and thinking outside the box. 

Thanks Terry, for the link to a broad variety of SDFat libraries. Good to know. Thanks

listen to Terry.

Michael,

your initial post is correct. you just need to add a diode and you will not see the 5v on pin 2. The lower the forward voltage of the diode, the better. I use this method to level shift RX TX from 5v to 3.3v and it works fine as well.  This is an acceptable way to level shift. For instance, Digi, which makes the XBEE modules, mentions this as one way to level shift.  The other option is to disable the internal pullup resistor of the atmega output pins going into the SD card. I have not tried this with SPI, but it works fine with TWI, for which both SDA and SCL are bidirectional.

I have this exact SD card and adding a diode is all I did with input signal pins (no need to do anything to output pins) and it works perfectly fine. Just make sure you are not getting higher than 3.3.v on the input pins. What you will be stressing with the higher voltage is not the SD card module but the SD card itself.

did you configure both A4 and A5 as input first?
It does not matter what the pullup on your board is. what matters is the cpu internal pullup is to 5v and your sensor board pullup is to 3.3v and you don't want to mix them. A4 and A5 are special pins that are open collector specifically designed so if you disable the internal pull up, only the external pullup wll be used. its all in the atmega328 datasheet if you want to read about it.

http://arduino.cc/en/Reference/DigitalWrite

you must disable the internal pullups to A4 and A5 if you are not using a logic level converter.

just to add, I ran into an opposite problem when I connected this to an 8 channel relay board, which already comes with its own diode circuit connected to supply rail. In my case, I connected pin 10 to Vcc and was getting unpredictable results, until I disconnected pin 10.

search ebay for dc-dc buck converter. costs under $2.

ah, thanks, I should have thought of googling the label on the buzzer.

http://www.qinlon.com/products.asp?Action=Detail&ID=148

thanks. I have that type, its not the same. nowhere near as loud as the one in lipo alarm. this one is not just a cylinder shape. it has a small rectangular opening on one side (pointing away from the pcb in the picture).

if you have ever triggered your smoke detector alarm, its about that loud.

anyone know where I can buy this type of buzzer? (buzzer used in a lipo battery alarm). the buzzer is small but really loud.
worse case I can just buy the lipo alarm ($1.88 and it comes with two buzzers) and just remove the buzzer.

is it correct that you can only have 2GB max partition size with fat16?

If it was not the last shield in the stack you would not be able to see the LCD!

right, it does not make sense to be able to stack another shield on top, but that does not mean you should not be able to use the unused pins anymore. I believe the lcd shield has through holes to solder a female header so you can use jumper wires to use the pins not used by the lcd shield.

were you able to succesfully do a write with "always update firmware" checked?
the unbrick procedure is basically to update the firmware again.

note that if you actually did update the firmware, the baud rate will go back to default of 9600.

If you don't use an xbee explorer or USB to serial adapter, then it is impossible for you to update the firmware. Writing the parameters is not updating the firmware