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Gavinmc42
Posts: 1497
Joined: Wed Aug 28, 2013 3:31 am

GPU LED blinking

Sat Oct 14, 2017 9:40 am

Lots of baremetal is about booting the VC4 and then switching the ARM on and doing stuff on the ARM.

OpenCL on VC4 has got me thinking about the GPU/QPU

Has anyone blinked a GPIO LED with QPU code?
Activity led is initially under VPU control on boot?

Been wondering if the QPU's could be used as real time controllers
Nanokernel's in QPU?
I have not seen QPU specific timers, VPU's have any?

I assume the ThreedX OS is running in one VPU after bootcode.bin is running.
This would leave the other VPU free, unless the ThreadX is running multicores :o
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

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Akane
Posts: 41
Joined: Tue May 27, 2014 1:20 pm
Location: Tsukuba, Japan

Re: GPU LED blinking

Sat Oct 14, 2017 10:01 am

Dom, who is an engineer at Pi Towers, said QPU cannot access the peripheral bus: viewtopic.php?f=72&t=128309. So it's unlikely I think.

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Gavinmc42
Posts: 1497
Joined: Wed Aug 28, 2013 3:31 am

Re: GPU LED blinking

Sat Oct 14, 2017 10:16 am

Thanks.
Unlikely unless QPU's can access memory directly?

So probably need to stick to just the VPU.
Start with the alternative bootloaders for examples.
Is there a VPU C compiler? google time.
GCC on Videocore :D probably better to use LLVM?
Time to learn something new LLVM :D
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

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