AM3351: UART data received during standby mode

Junpei Kishi

Part Number: AM3351

Hi team,

I would like to ask the processor can receive correctly UART data which is transmitted during standby mode.

The goal is that the processor wake itself up by UART input, and manage the data correctly.
However, I heard AM335x support only GPIO as wakeup source, so the PAD should be configured as GPIO before entering standby mode.

Do you have any solution to manage UART packet correctly with using as wake up source?

Best Regards,
Junpei

over 3 years ago

0 PaulM over 3 years ago

TI__Mastermind 28215 points

Which UART are you using?

0 Junpei Kishi over 3 years ago in reply to PaulM

TI__Intellectual 865 points

Paul-san,

I didn't decide yet.
But hopefully 2 or more UART channels can be managed.

Best,
Junpei

0 PaulM over 3 years ago in reply to Junpei Kishi

TI__Mastermind 28215 points

Junpei

There are actually 7 different wake up sources. These are detailed in section 8.1.4.5 of the device TRM (Rev Q). Since several UARTs may be needed as wake-up sources in your application, you can use the UARTs that are muxed with GPIO0 (only GPIO wake-up source).

--Paul

0 Junpei Kishi over 3 years ago in reply to PaulM

TI__Intellectual 865 points

Hi Paul-san,

Could you let me check my understands?

For UART0, it can be wake up source, and can manage received data while resuming without data lost.
For other UARTs, it can be wake up source with muxing with GPIO0, and the received data while resuming will be lost.

I understand the level changes of signals can be wake up source, but I concern whether the received data by resuming fully will be lost or not.
We will use Linux on this device, so I will be happy if the way is available to manage them using Linux driver.

Best Regards,
Junpei

0 PaulM over 3 years ago in reply to Junpei Kishi

TI__Mastermind 28215 points

Junpei

I am checking to see if the UART can capture the data while resuming. I'll provide an update later today or Monday.

--Paul

0 PaulM over 3 years ago in reply to PaulM

TI__Mastermind 28215 points

Junpei

The UART wake-up event is just looking for a transition on the UART. No data will be captured. It is recommended that the wake-up source send a dummy word to wake-up the processor.

Paul

0 Junpei Kishi over 3 years ago in reply to PaulM

TI__Intellectual 865 points

Paul-san,

Thanks for your telling the facts.

How long does it take to ready for receiving data correctly from standby mode?
I saw it takes usually 2-300ms, but if it's true, over 2KB data will fail to be captured.

We are considering one way communication using IR, so it's hard to report when ready.

Best,
Junpei

0 PaulM over 3 years ago in reply to Junpei Kishi

TI__Mastermind 28215 points

I would suspect that the time is dependent on the s/w used and configuration employed.

Can you give me which SDK you are using so I can get the right people to comment?

Paul

0 Junpei Kishi over 3 years ago in reply to PaulM

TI__Intellectual 865 points

We are using the latest Linux SDK.

Regards,
Junpei

+1 Bin Liu over 3 years ago in reply to Junpei Kishi

TI__Guru**** 169941 points

Hi Junpei,

To avoid data loss on UART0, I think you should use hardware flow control, so that the device which is connected to UART0 won't send data until the Linux system is resumed and ready to accept data.

0 Junpei Kishi over 3 years ago in reply to Bin Liu

TI__Intellectual 865 points

Liu-san,

I see.
Thanks for giving information.

It looks hard to configure stand-alone strategy if we use one-way communication on UART.
I will check the requirement again.

Best Regards,
Junpei

Processors

Processors forum

AM3351: UART data received during standby mode