BBAi pinmapping / temperature

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Hello everyone!

I am thinking of switching from a beaglebone black to a BBAi to improve performance of our system. Right now we are using a custom cape for the BBB. I wondering if we could have the came pin functions of the BBAi if we swap it out without any redesign to the cape. Ie does anyone know if the BBAi have the same pin I/O as the BBB? I read that we would need to set the pinmux for the BBAi, but other than that are there can we get a 1 to 1 swap of both boards? I read in some posts that you could in theory, but there seems to be very limited documentation on the BBAi pin mapping. If anyone knows where I could find that, it would be super helpful.

On second topic, we were having some issues with the BBAi overheating and becoming unstable. Are there any suggestions of how to limit this issue without having to add supplemental active cooling (ie anything kernel/clock related)?

Thanks!

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Capes

I can not find the web-page, but I remember reading the BB Black and BB AI Capes were compatible, except something like a different I²C device was used and some GPIO were connected together on BB AI to provide both functions of the BB Black.

Overheating

With no a fan, the heat sink is too small. The heat sink temperature rises too quickly for older software image to lower the clock speed, before the temperature is too high and the processor (SoC) stops.

This would imply, you need:

  • a fan
  • a bigger heat-sink
  • a lower clock speed
  • a newer software image
    Fan 1

I bought a 5V 20mm fan, used nylon screws to attach it to heat-sink, soldered some header to the wires, connected the header to +3.3V and GND on P9.

This works well. However, this stops you using capes, fans have a limited life, and you need space for an air flow.

Fan 2

I designed and made my own Fan Cape, I used a 5V 32mm fan.

This works well. However, fans have a limited life, and you need space for an air flow.

Bigger Heat-sink

I have not had time to investigate this.

I plan to attach a sheet of aluminium 100mm 100mm 5mm to the existing heat-sink or directly to the processor.
The sheet would have cut outs for RJ45, USB, Cape P8, and Cape P9. The first Cape would be spaced away cape through socket-plug without a cape.

However, this will make the package much bigger. A thick metal box could act as heat-sink, if you can get the heat from the processor to the box.

Clock Speed

Similar sized system-on-chips run at 200MHz to 500MHz without need of heat-sink.

The speed throttle seems to be a software process, therefore you must be able to set the speed in software.

However, you may not have the speed for your application.

New Software Image

My beagle board came with an image which worked to throttle the clock speed. It asks/suggests you upgrade to the latest image. I, like many others, upgraded the image, only to have a system which overheated in about 30 seconds. Fortunately, this was just enough time to upgrade the image again.

However, you may not have the processor speed for your application.

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Here are a couple of sources that were posted sometime back I believe by Jason.

https://github.com/beagleboard/beaglebone-ai/wiki/System-Reference-Manual#p9.11-p9.13

https://docs.google.com/spreadsheets/d/1fE-AsDZvJ-bBwzNBj1_sPDrutvEvsmARqFwvbw_HkrE/edit#gid=1518010293

This should help deciphering the pin mapping.

Cheers,

Jon