ADXL345 I2C Accelerometer NOT WORKING

[jhersh]

If you are stuck in read, that usually means that one of the I2C lines are stuck low. Make sure there are no shorts on your sensor.

Joe

[xisybyl]

We tried more than one.

[Phalanx]

I've experienced quite a variety of issues, but let me share what I have done to get it finally working to some degree. This is using the Labview example with I2C interface only.

1) Make sure the cable you use to connect from the CRIO to Digital Side Car is correctly pinned and in proper working order.
a) We found our round molded ones from previous years to be faulty as others have described here.
b) We tried the ribbon cable from last season (from Andymark irrc) which also did not work for us.
c) We repaired this years ribbon cable, which does work.

2) Make sure your connections to the accelerometer as well as to the digital side car are clean and good. It appears from my testing the I2C is very very sensitive to poorly made cables and it will have a large impact on it's ability to communicate.

3) When using the example I2C, I found I had better success when I ran the driver station application on the same laptop as the example. I noticed in the example code an open/close for the driver station so I started running it.

4) Even with all of the above, sometimes it works, sometimes it fails to respond, sometimes it works for a while, then fails. All the failures are a failure to respond.

[jhersh]

Originally Posted by xisybyl

We tried more than one.

Another way this can happen is if the sensor is not powered. Are all the power supply LEDs lit on the digital sidecar?

[Bob649]

Hello all,
I found it - it was multiple faulty cables to the sidecar. The only one that works is a new flat cable from this year that I repaired according to the instructions on the KoP site. It looks like I probably had two problems at the beginning and after I fixed the other one, had the faulty cable issue. Once I got it running, it has been stable.

I will post some photos is anyone is interested in seeing some documentation of an end to end system including some scope shots of traffic.
I guess the "bad" cables must be good enough for the low order PWMs and other channels we were using to fool me.

So the moral of the story, even if you are sure your round cable is good, ONLY use a new flat cable without a twist until you get it working. Then switch other items one at a time so if it stops working you know what it was that went wrong.

Thanks to all who replied!

Bob

[jhersh]

Glad you got it working. I'm surprised at the problems people are having with this. It has always worked great for me... But I guess that's how it goes.

[xisybyl]

"That's how it goes" is not what I expect to hear from NI. We only have one ribbon cable and we can't get our accelerometer to work with it. Why doesn't the round cable work? We checked it for continuity & shorts. Or perhaps the problem is really not the cable? Does anyone know where we can buy a cable that WILL work reliably?

[jhersh]

The only "bad cables" I've heard reasonable explanations for are the round cables that Joe Ross reported do not have all of the pins connected. As for the other reports, I have no idea how much of that is speculation or other variables that are not being accurately conveyed here. The I2C signals only operate around 150kHz on the digital side car, so I don't expect any there is any cable quality problem that would cause issues, short of "the pins aren't connected at all". I suspect there are other problems like poor soldering, very long cables between the DSC and the sensor, damaged sensors due to hooking up power and ground backward and some point in the past, etc.

-Joe

[agartner01]

Could someone take a look at this thread:http://www.chiefdelphi.com/forums/sh...d.php?t=101921 same problems in c++.