ricckma
Member
It's said that they are compatible, but just want to make sure. Here's the link to the Logger Shield
Or had anyone tried to use the maple leaf for data sampling/logging purposes, e.g. writing the data to a SD card? I would really appreciate it if you could share your experience with me.
Thanks
Ricck
poslathian
LeafLabs
Thats a neat shield. It looks like from the schematic (http://www.ladyada.net/images/logshield/logschemv1.png) that the SD card interfaces over D10-13 using the SPI protocol. Intentionally, these pins are an exact match for the hardware spi on stm32. The RTC clock interfaces via I2C on pins 19 and 20 (aka A4 and A5), which are GPIO on maple. The breadboard on the side is likely going to be flush with our expansion header, which might be good or bad depending on what you want. You can always pop it off with some solder wick.
Will it run "out of the box"? probably not, I assume there is some AVR specific code in the SDFAT libs that you can use with this board. I'm not sure how much porting there would be, probably not a whole lot. I'll take a look and see how tractable it is. On the bright side, the hardware spi connection to the flash card means one could theoretically shuffle data into and out of the sd card and high speed and using the DMA (very efficiently!).
TLDR: Looks good, libs might need some porting.
poslathian
LeafLabs
So i just looked through the sdfat code some (the lib used with the adafruit shield) and it looks like the whole thing is surprisingly not AVR dependent. In fact, it depends in a few places on avr/pgmspace.h, which allows users to use the flash memory onboard the avr. We (leaflabs) dont yet but will soon support most of the functions in pgmspace.h. The library has one monolithic pin mapping file, it should be straightforward to add out own pin def's here. The rest of the work depends mostly on spi reads and writes, calls to pinmode, digitalwrite, and other wiring based functions which we support. The only thing Im not sure about is that the adafruit shield has a 5V to 3.3V level shift, since the arduino is a 5V platform and the SD cards are 3.3V devices. Maple, on the other hand, is a 3.3V device, and a level shifter isnt needed. I'm not entirely certain what happens when you shift 3.3 to 3.3, probably nothing.
Conclusion:
with a little work this shield and the lib can be made to work with Maple. I'm going to pin the sdFat maintainer about it, maybe we can do a port of his lib for Maple. It seems a lot of people use sdFat.
stephani
Member
Hey Rick,
I'm trying to do the same thing, and I'm hoping since it's been a year, you have figured out if it was feasible to do and if so, how much extra work did you have to do to make it work?
The Maple seems so awesome, and our other choice, the Mega 2560, isn't an exact fit with the shield either and will require extra work. I just want to know which route has the least amount of extra work because of time restrictions. Thanks in advance!
Cheers :)
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