Memsic 2125 code?

[ScaleRobotics]

Hi Ed,

I'm with you. There SHOULD be something like you suggest. There is in the higher ranges that's merged with 9dof type higher priced stuff. But what you want is simpler.
So you want a pitch and roll sensor that outputs in degrees. What type of interface would you like? Serial or i2c or other?

[Ramius]

Hi Walter,
Thank you for your input and assistance with this project. Years ago when I was working on a compass things were similar with requiring complex code and higher math which were not necessary as I later discovered. I have to believe that the people building robots must have a simple way to keep their robot "balanced". Again, going back to the Subtech APC-3 and 4 these Automatic Pitch Controllers which drive a servo were on the market long before the code using the "trig" include was created. My use is to take the outputs from the sensor store in in a variable to display on a "BOB-4" on screen display. The sub has a periscope camera which provides the video for a FPV with the subs operational data displayed. Best, Ed

[cncmachineguy]

Hi Ramius, Can you provide links to the equipment you are using? At least for the FPV stuff and the BOB-4? It will be intresting to see what kind of data it requires to add to the sub's operational data displayed.

[ScaleRobotics]

I have to believe that the people building robots must have a simple way to keep their robot "balanced". Again, going back to the Subtech APC-3 and 4 these Automatic Pitch Controllers which drive a servo were on the market long before the code using the "trig" include was created.

Hi Ed,
I suspect that the Subtech APC-3 or 4 may not really care about angle, and just looks at how far off a neutral horizon you are, adjusting the pitch accordingly (much like some simpler robots). It may use a lookup table of some sort to do this, or some math, or a combination of the two. From what I read about one of the sensors mentioned (in another forum) PitchControlStamp LR2 , it doesn't really state if it is working off a 1,2 or 3 axis accelerometer. As I mentioned earlier, a lookup table could get you close for angle. For example, at 75 degrees a (1 axis) pitch lookup table would start to get off by more than 3 degrees, and even more if there was any roll involved. This error goes up to about 10 degrees as you approach 90 degrees. And remember with some roll involved, it would be much higher error. Perhaps there is not much roll in a sub, I am not sure. If these are close enough, then certainly it can be done with a lookup table, and many on this site, including myself would be willing to help you with that. As for cost of on the market pitch controllers, even the Subtech parts look to be about $55 each, the LR2 $95 each, and both seem to only control 1 axis.

Looking up your ideal sensor made us realize there is a need for an inexpensive sensor that outputs an angle. I did find this one, and it fit the bill, all except for the inexpensive part: http://www.sparkfun.com/products/8656 .

We are making a similar sensor, giving an angle output for Pitch, Roll and a tilt compensated compass heading. But price will be much less. It should take about 4 weeks to get the PCB made and code finalized.

[Ramius]

Hi cncmachineguy,

Here is the link for the OSD http://www.decadenet.com/bob4/bob4.html . It allows 40 characters by 22 lines. In the past I looked at the OSD-232+ and it only allowed 30 columns by 12 rows. Have not yet finalized the goggles yet, there are a few considerations such a if they underscan the video or overscan and if I can shift the display on one display horizontally as this would allow for a "3-D" effect!

Walter, if you are playing with compasses then maybe look at http://www.robsonco.com/Dinsmore/Untitled_5.html .


Best, Ed

[Ramius]

Hi Walter,I have looked and looked and looked at all this different information and it still has me very lost and confused. I need to calculate the PWM outputs to acceleration, then take the arcsine of the acceleration determine the angle of incination. I know you suggested using a look-up table and I have never done this before and not sure how it is done. Basically I am asking how is the code written in simple terms I can study. Thanks, Ed