Oh, boy. I have been struggling with heading not related issues now for quite some time. Had not reflow soldered and more importantly applied solder paste by hand for tiny things for a while and the skill has left me. Tried two boards and none was good. The components are kind of too close to each other to re-work easily and then I ran out of parts. This is what happens to the projects of this complexity. It is sometimes harder to get to solving the problem than solving it
.
Anyway, with missing parts on order and with some discretionary time I browsed some more for what solutions are out there. I stumbled across
this - 1.6x1.6x0.5mm sensor fusion co-processor that runs at 1/10th of power of most powerful enough processors for the task. It is available on a module like
this, as well. The module claims to achieve 2 degree RMS heading error.
I have also come across
Maxim Integrated MAX21100, but sadly it is out of production.
The benefit of the above solutions is no software to mess with. The down-side, of course, is you are dependent on yet another black box in your project. However, if I can get a heading with error below something I will ever be able to produce with picaxe and in ~3mm2 of board space including passives, I confess, I would give up on picaxe for the task
. How can one obtain the SENtral thing is, however, a mystery for now.
Then there is
LIS331EB from ST - an ARM processor with accelerometer built in. The bad thing with this is that you have to install the firmware yourself, but it seems to be available. Feels a bit like Arduino, though, where you compile God knows what and hope that it will work and most of the times it does, but if it does not you are stuck with trying to find bugs in code you have not written.
Finally, there is
this company with sensor fusion chip that is basically a cortex something processor. Same story as above, but I get less of an impression there is easily available firmware to just install. It sounds more like we have a nice chip you can develop your software on.
Edmunds