Setting GPOs at a very high rate

Martin H.

Other Parts Discussed in Thread: AM3359

Hi,

my aim is to do GPO outputs (32 bits simultaneously, AM3359) at a very high rate. I
experienced some considerable irregularities: the output sequence is not continuous and jitters when the number of outputs is high.

So my question is what has to be considered to have a stable ouput sequence. The period of the square wave signal I would like to achieve is 80ns.

What is the exact timing for GPO outputs?

Thank you.

Regards,
Martin H.

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi Martin,

This is 12.5MHz frequency. What software are you using? You will not be able to achieve this on a GPIO under Linux due to SW and HW latencies. Have you considered using the PRU for this purpose?

0 Martin H. over 9 years ago in reply to Biser Gatchev-XID

Expert 2315 points

Hi Biser,
yes, I had taken that into consideration, but I need 32 simultaneous outputs and - as far as I remember - a PRU only has 15.
Is there some literature that explains in detail what is going on and how latency can be minimized for a 'normal' GPO?
Thank you.

Regards,
Martin H.

0 Biser Gatchev-XID over 9 years ago in reply to Martin H.

TI__Guru**** 393215 points

Yes, it's true that the PRU has only 16 outputs. With a normal GPIO you might be able to achieve this only if you use bare-metal programming. I'm afraid there is no literature that covers AM335X GPIO latencies. There have been a lot of posts on this forum on this topic. Here are a few:

https://e2e.ti.com/support/arm/sitara_arm/f/791/t/252598
http://e2e.ti.com/support/arm/sitara_arm/f/791/t/202814
https://e2e.ti.com/support/arm/sitara_arm/f/791/t/445958

0 Martin H. over 9 years ago in reply to Biser Gatchev-XID

Expert 2315 points

Thank you, Biser!

Regards,
Martin H.

Processors

Processors forum

Setting GPOs at a very high rate