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Topic: Which 9/10dof? (Read 1 time) previous topic - next topic

robvoi

Dec 12, 2012, 04:22 pm Last Edit: Dec 12, 2012, 04:59 pm by robvoi Reason: 1
Hi,

is there any advice regarding which 9/10dof device to choose?
I have no clear project yet. Just some ideas and I want to get started using an xDoF sensor.

The two (payable) options I see are:
http://www.ebay.de/itm/9DOF-ITG3205-ADXL345-HMC5883L-IMU-MWC-Arduino-Compatible-/180893188799?pt=LH_DefaultDomain_0&hash=item2a1e1302bf
http://www.ebay.de/itm/New-10DOF-9-axis-Attitude-Indicator-L3G4200D-ADXL345-HMC5883L-BMP085-Module-/350646462688?pt=LH_DefaultDomain_0&hash=item51a42868e0

Do I get it right that I can use I2C for all sensors and with this only need two data wires?

Thanks
Robert

lesto

take the 10DOF, and yes, on i2c with only 2 pin (and 2 pullup at 2.2k and internal puul-up removed commenting the line in twi.h inside Wire library, and same logic level, you'll need a levelshifter if the sensor are 3,3v)
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Krodal

That 10DOF looks good to me.
It seems to have a voltage regulator, so you can use it at +5V.
The i2c signals can do without level shifter. Read the story here: http://playground.arduino.cc/Main/I2CBi-directionalLevelShifter

Normally two pullup resistors (preferrably 4k7) to 3.3V are needed with these sensors. But it seems that there are already pullup resistors on that sensor board.

lesto

uhmm have has strange behaviour in the past. That is an hack, and remember that high level in arduino isn't 2,5V but is slight above 3V, so you are really on the edge.

From your linked page:
Quote
Of course, following the official I2C specification (stronger pullup resistors) and avoiding higher voltage signals at any 3.3V chip is best. Any "serious" project should follow all technical specifications.
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Krodal

#4
Dec 12, 2012, 07:25 pm Last Edit: Dec 12, 2012, 07:29 pm by Krodal Reason: 1
Ok, I will add it to that page.
I read the datasheet and a 'high' should be 0.7 * Vcc. So 0.7 * 5V = 3.5V (minimum required voltage for logic high).

Chagrin

Both of these sensors already have level translators on the board. The little 6-pin chip is the translator.

Krodal


Both of these sensors already have level translators on the board. The little 6-pin chip is the translator.

Now I see it!   So they can be used just as they are. Although 2k2 pull-up resistors on both side (resulting in a 1k pull-up) seems rather low to me.

robvoi

Thanks a lot for all the replys! I took the 10dof.
30 to 40 days to go. Than I can start playing :-)

lesto

technically you should calculate the value everytime, but 2.2k is a "jolly", works every time :)
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