wondering if anyone has tried using the SD16 on MSP430F2013 configured
to do AtoD conversion on multiple (external) input channels. So far
I've been able to read a single axis on the accelerometer, reading all
3 axes in sequential pattern has not been possible so far. any help /
guidance is highly appreciated...

thanks
C
------------------------------------



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--- On Wed, 9/3/08, Chinmay Manohar wrote:

> From: Chinmay Manohar
> Subject: [msp430] help needed with interfacing 3-axis accelerometer with MSP430F2013
> To: m...@yahoogroups.com
> Date: Wednesday, September 3, 2008, 2:06 PM
> wondering if anyone has tried using the SD16 on MSP430F2013
> configured
> to do AtoD conversion on multiple (external) input
> channels. So far
> I've been able to read a single axis on the
> accelerometer, reading all
> 3 axes in sequential pattern has not been possible so far.
> any help /
> guidance is highly appreciated...
>
> thanks
> C

Hello C.
I am using an F2013 for converting 3 channels: 2 bipolar differential, 1 unipolar.
First of all, you have to set P1SEL bits to 1 for the input pins of the SD16 channels being used. Then, in order for the SD16 to work correctly, you must only enable the analog input on SD16AE register for the channel being converted. Also, since you are switching channels you must set SD16INTDLY_X to 3 or 4, in order to obtain a valid result. Finally, if you are using the internal refference generator AND channel 1 in differential mode (e.g A1+ - A1-), P1SEL.3 must be set to 0, otherwise, the reference voltage will be buffered on P1.3 pin and might damage whatever you are meassuring. That's all I can think of.
Kind regards,
Juan

------------------------------------



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For most accelerometer applications the SD16 is not a good choice, since
the measurements are not even close to being time aligned. This slew
means that the motion relationships between axes cannot be relied upon.
You are better off using either a digital output sensor, such as the PWM
output, or one with a serial output, since in the first case the micro
in edge trigger mode will store edges simultaneously, even though they
are not accessed precisely together, while in the serial systems most of
them convert sycnhronously so that data is time aligned. The downside to
most serial systems is that they limit each result to 8 bits. The next
best option would be to use a device with a SAR converter, such as the
2012,. Even though these are not sampled synchronously, so there is
still some time skew, the delay between samples can be much shorter than
with the Sd16 module, for the same resolution.

if you're stuck wit the 2013 then follow Juans recommendations.

Al

Chinmay Manohar wrote:

>wondering if anyone has tried using the SD16 on MSP430F2013 configured
>to do AtoD conversion on multiple (external) input channels. So far
>I've been able to read a single axis on the accelerometer, reading all
>3 axes in sequential pattern has not been possible so far. any help /
>guidance is highly appreciated...
>
>thanks
>C
>------------------------------------



(You need to be a member of msp430 -- send a blank email to msp430-subscribe@yahoogroups.com )

Thanks OneStone and Juan,

Currently I am not that concerned with the time gap between the three
axis, also for design purpose we are stuck with 2013 at the moment but
I will take your suggestion into consideration when in my next update.

thanks so much for your help

Chinmay
--- In m...@yahoogroups.com, Onestone wrote:
>
> For most accelerometer applications the SD16 is not a good choice,
since
> the measurements are not even close to being time aligned. This slew
> means that the motion relationships between axes cannot be relied
upon.
> You are better off using either a digital output sensor, such as the
PWM
> output, or one with a serial output, since in the first case the
micro
> in edge trigger mode will store edges simultaneously, even though
they
> are not accessed precisely together, while in the serial systems
most of
> them convert sycnhronously so that data is time aligned. The
downside to
> most serial systems is that they limit each result to 8 bits. The
next
> best option would be to use a device with a SAR converter, such as
the
> 2012,. Even though these are not sampled synchronously, so there is
> still some time skew, the delay between samples can be much shorter
than
> with the Sd16 module, for the same resolution.
>
> if you're stuck wit the 2013 then follow Juans recommendations.
>
> Al
>
> Chinmay Manohar wrote:
>
> >wondering if anyone has tried using the SD16 on MSP430F2013
configured
> >to do AtoD conversion on multiple (external) input channels. So far
> >I've been able to read a single axis on the accelerometer, reading
all
> >3 axes in sequential pattern has not been possible so far. any help
/
> >guidance is highly appreciated...
> >
> >thanks
> >C
> >
> >
> >------------------------------------
> >
> >
> >
> >



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