[psas-avionics] IMU parts

I kirkpad at pdx.edu
Mon Sep 7 00:30:58 PDT 2009

Andrew and Tim,
I'm working up a schematic for an IMU and I have a couple of questions  
you might be able to answer...

First, Analog devices finally came out with a 3 axis accelerometer  
with decent range (8/2009). The ADXL326 has 3 axis +-16 g's. Noise  
spec is comparable but a bit lower than previous offerings. Basically,  
was there any reason not to use the 321's (or this new part)? I'm just  
wondering if anything stands out in your minds from other  
accelerometer work you've done.

Second, I'm looking at the ADS1278 24 bit ADC, and I'm a bit spooked  
by the clock requirements. It needs a high speed clock that is as fast  
as, or a power of 2 faster than, the spi clock. I haven't seen a good  
"clock out" from the LPC2378 that would be selectable (in speed).  
Before I place a CPLD, had either of you considered this when  
exploring the other ADS variants with capstone students? The demo  
board has some weird D-latches on the SPI outputs as well... Yuk!

With the AD part and the new z axis IDG parts (they finally put a temp  
sensor on, as well), I can get it done on one board with no orthogonal  
daughter boards. I'm thinking this will be easier than the ones I've  
done in the past...


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