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A Motion Coprocessor Without The Proprietary Layer

When you have a complex task that would sap the time and energy of your microprocessor, it makes sense to offload it to another piece of hardware. We are all used to this in the form of the graphics chipsets our computers use — specialised processors whose computing power in that specific task easily outshines that of our main CPU. This offloading of tasks is just as relevant at the microcontroller level too. One example is the EM Microelectronics EM7180 motion co-processor. It takes input from a 3-axis gyroscope/accelerometer and magnetometer, acting for all intents and purposes as a fit-and-forget component. Given an EM7810, your host can determine its heading and speed at a simple command, with no need for any hard work.

[Kris Winer] used the EM7810, but frustrated at its shortcomings decided to create a more versatile alternative. The result is a small PCB holding a Maxim MAX32660 ARM Cortex M4F microcontroller and the relevant sensors, with the MAX32660’s increased power and integrated flash easily eclipsing the EM7810.

As a design exercise it’s an interesting read even if you have no need for one. His write-up goes into detail on the state of the motion coprocessor art, and then looks carefully at pushing the limits of what is possible using an inexpensive PCB fabrication house such as OSH Park — you can get this chip as a Wafer-Level Package (WLP) which is definitely off-limits. Even with the TQFN-24 he picked though, the result is a tiny board and we’re happy to see it as an entry in the Return of the Square Inch Project!

It is perhaps surprising how few projects like this one make it into our sphere, as a community we tend to focus upon making one processor do all the hard work. But with the ready availability of inexpensive and powerful devices, perhaps this is an approach that we should reconsider.

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