BeagleBone Blue – A complete, Linux-enabled robotics computer

Re:BeagleBone Blue – A complete, Linux-enabled robotics comp... by ajross on Wednesday March 15, 2017 @09:44AM (#13876007)

There are two lines in the spec summary. The PRU is one, a Cortex M3 is another. It's not unliklely that the SoC indeed has both, intending the ARM for use as a very low power, always-on sensor listener (e.g. the DSPs that handle audio and sensor input on phones so they can wake up the main CPUs for gesture or voice recognition).

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Re:BeagleBone Blue – A complete, Linux-enabled robotics comp... by fnj on Wednesday March 15, 2017 @10:14AM (#13876218)

Except the datasheet [0] does not list anywhere "Cortex-M3", nor reference any ARM cores other than the Cortex-A8. So if it is there, they are keeping it a deep secret.

[0] http://octavosystems.com/octavosystems.com/wp-content/upload...

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Re:BeagleBone Blue – A complete, Linux-enabled robotics comp... by mrob on Wednesday March 15, 2017 @10:59AM (#13876540)

It's used for power management, and it's listed in the full Technical Reference Manual, page 1172:

http://www.ti.com/lit/pdf/spruh73

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Re:BeagleBone Blue – A complete, Linux-enabled robotics comp... by smilekzs on Wednesday March 15, 2017 @02:24PM (#13878479)

What a surprising find! I would imagine Cortex-M3 (with 24 KiB RAM in total) a huge overkill for just power management. And it totally escapes me why the realtime co-processors are using a custom ISA solution rather than just using Cortex-M0/3/4. Would have been great to leverage the mature toolchain for Cortex-M!

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Re:BeagleBone Blue – A complete, Linux-enabled robotics comp... by ajross on Wednesday March 15, 2017 @03:31PM (#13879036)

Power management on modern SoCs is actually really complicated. There are dozens of power rails and clocks for different subsystems that all must be brought up and down with controlled order and timing if the device is going to work reliably. This kind of controller is routine on most "big" SoCs these days.

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Re:BeagleBone Blue – A complete, Linux-enabled robotics comp... by smilekzs on Thursday March 16, 2017 @03:50AM (#13883275)

Then how about Cortex-M0, instead of M3? Surely enough that can save quite a bit of area, while still enjoying the good interrupt support of Cortex-M?

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Re:BeagleBone Blue – A complete, Linux-enabled robotics comp... by ajross on Thursday March 16, 2017 @12:11PM (#13886208)

Presumably so they can share the workload with other tasks, like boot verification or low power sensor listening. The M3/M4 are still very small cores.

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