I2C errors on NanoWii

[Andy7]

Hi,
I've just connected a BMP085 to my NanoWii (just a couple of quid from Hong Hong!).

-- now, this bit is probably a red herring, but read on to get to the real problem
At first, when I enabled the sensor in the MultiWii software, my system did something a little odd. It started up with the motors running in idle. From the ESC beeps, it sounded like it was doing a throttle calibration, so I jumped to hold the quad down least it bounce off the ceiling, but the motors continued to run on idle speed until I pulled the power.
On subsequent restart, the escs were giving a "throttle not at min" error. I took off the props and ran the ESC calibration a couple of times and all was okay.
-- Now that was odd but unrelated to my REAL problem here.

When I looked at the sensor trace in the GUI, I found that I was getting CRAZY values from the ACC, just random junk. Plus loads of I2C errors being logged.
I figured that my cable (about 7cm) was probably too long and picking up noise, so I halved it. Now, that got things back in order and all sensors were bahaving as I'd always seen them. YAY, even seeing BARO changes when lifting the quad up and down.

Then noticed that in that time I'd clocked up about 5000 I2C errors. Odd...
I've got the I2C clock speed on the lower of the two settings in the config, tried pullup resistors on and off but still geting errors. (Now, as I said before, the sensor trace looks good, no spikes, good, clean, responsive).

I was worried that I'd damaged my board so I pulled out a spare (still with the shipping version of MultiWii on it). I connected it to my laptop, good clean ACC trace and NO I2C errors.
Next, I flashed it with the code I'm currently running... and the board (straight out of the packet) gives the same rate of I2C errors as the one on my quad.

Anyone seen this before and know what's happening?

Cheers,

Andy

[Andy7]

Interesting. I read the big post about I2C errors. A great article.
It looks like those errors might have been there all along on the nanowii but I hadn't noticed. Seems that earlier versions of multiwii wasn't logging the errors hence my out of the packet board showing no errors.

Which leads me to the question... Does the nanowii have signal level / pull-up problems with the inboard ACC?

I guess a look at the schematics might shed a little light on that as to whether the Arduino is a 3.3v device or 5v.

I'd be shocked if there were hardware problems there because it looks like a very professionally made board.