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The speed for storage data in FEZ


#1

Hi, in our new project, we need a high Accuracy 3-axis accelerometer. So we will need a 16 bit ADC and sampling the 3-axis accelerometer at 200HZ-500HZ sampling rate and store the 3-axis acceleration data in real time.
Does the speed of SD card or the usb storage can fit my demand?
Any suggestion? Do I need a FEZ has SDRAM?
Thanks.


#2

USB is faster than SD


#3

Tzu, don’t expect anyone to tell you here: yes, it will be possible (damn, I just did :p). I think you’ll have to run some tests on a real device.

I also wonder why you would store accelerometer data at 500Hz? Are you building a Black box for earthquakes?


#4

Ha, yes for for the earthquakes.
So do you has same experience?
what accelerometer and ADC do you used, do you store in the SD card.?
I am finding good accelerometer and ADC.
The most accelerometers and ADC on NETMF field or Ardunio are not suitable.


#5

NETMF is not real time but file access speed is about 200KBytes/sec.


#6

The speed will also depend on the SD card/flash drive. They are not created equal.

Maybe try this test on both:

http://www.tinyclr.com/forum/1/1858/

If you have 3 channels at 16 bits each, and and extra 8 bits per channel for “header” info, you need approximately 35kb/s (kiloBITS per second) transfer at 500 Hz. This seems doable as other people seem to get better than 100kb/s performance.

You might have a tough time sustaining 500 Hz on NETMF alone. It will depend on how fast you can read from the AD, process and write to SD. Only one way to find out and that is to try it! (or read all the technical specs of all the components in great detail :))