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Topic: Pressure Sensor Array (Read 1 time) previous topic - next topic

andmok

Hello,
I'm am trying to create a pressure sensor array to be placed around the airfoil of a wing. The array would consist of around 20 pressure sensor devices and I would like the ability to collect data from the sensors simultaneously. The pressure sensor that I would like to use for this project is the BMP085 www.bosch-sensortec.com/content/.../BST-BMP085-DS000-05.pdf there are other pressure sensors (http://www.freescale.com/files/sensors/doc/data_sheet/MPL115A1.pdf) that I could use, as well, that use SPI. So I am not necessarily limited to I2C. I would appreciate any suggestions on how to tackle this project, or any other posts or sources that you could suggest.

My main question is is it possible to talk to multiple devices at the same time using I2C with multiplexing? or would another interface be better such as SPI?

RuggedCircuits

It's possible to multiplex the BMP085's because they have a reset pin (called XCLR I think) which keeps them off the I2C bus when asserted. So you can keep most of them in reset, talk over I2C to one of them, then put it in reset, move on to another one, etc.

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kg4wsv

Quote
I would like the ability to collect data from the sensors simultaneously.


You won't be sampling simultaneously with either of these sensors; you'll be sampling sequentially.  It may be a really fast sequence, but it's still a sequence.

You need to do some analysis on the data you're looking for and see if sequential is good enough.

If it's not good enough, you need a way to trigger all the ADCs at once, and collect the data at your leisure.  The Analog AD760x (AD7606, AD7607, etc) devices have up to 8 ADCs for sampling 8 channels simultaneously.  You should be able to use multiple devices driven by a single trigger to sample more than 8 channels is a truly simultaneous manner (well, there's that whole electrical signal propagation/speed of light thing to deal with, for the truly pedantic).

-j

GoForSmoke

Wow, my first time on the forum, first thread viewed, and the OP is doing aerodynamics work! Not that I'm an AE mind you but fascinated by the subject.

You could connect the pressure sensors up to small, cheap Atmel chips (or even multiple Arduinos) to get and buffer the data when a trigger line is pulsed and have each transmit to a central collector in turn. Then you would have your snapshot. In a steady state situation it wouldn't matter, would it? But maybe you're not looking at steady state data.

Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

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