Power consumption issue in IMX250 in low Power mode when connected via RS232

[Muks26]

Hello ,

I am facing one issue in my code development for IMX250 , When connected via RS232 communication then when it is made in sleep mode then the power consumption taken by processor seems to be higher with the expected value. 

Let say it is taking 6MA in sleep mode but ideally it should be 1.2MA .

We found that when connected via RS232 then USB is also initialized but when we try to disable the usb then also there is no change in power consumption.

Can you please help me out in this ?

how to completely disable USB once it is initialized ?

@Powerconsumption

Regards,

Mukul Parihar

[Sanket_Parekh]

Hi @Muks26 

I hope you are doing well

->To disable the USB, One can try to disable the USB node from the device tree or by commenting the "vbus-supply" property for a particular USB node.

-> Or one can disable the PLL for the USB using the UPCTL register.

Please refer to section 15.4.1.3 USB PLL (UPLL) Domain Clock Generation from the reference manual IMX25RM.pdf.

Thanks & Regards

Sanket Parekh

[Muks26]

Thank you @Sanket_Parekh for your answer.

The suggestions you provided are being handled in our code.

But the thing is I am not seeing any power consumption change in sleep mode by doing these changes.

 Currently Behavior is when connected via USB it shows 1.2 MA in Sleep mode but when connected via RS232 it shows 6.5 MA in Sleep mode but ideally it should be the same for USB and RS232.

But the root cause is when connected via RS232 ,the USB initialization is causing this extra power consumption and when we directly return from the beginning it gives the expected power consumption in RS232 as well. 

Now the thing is why this is not being reduce when all the registers are disabled for USB when it is connected via RS232 ?

Any Idea on this ? it would be really appreciated.

Regards,

Mukul Parihar 

[Sanket_Parekh]

Hi @Muks26,

I hope you are doing well

Can you please explain your connection how you are connecting the USB via RS232?

when we directly return from the beginning it gives the expected power consumption in RS232 as well. 

=>Can you please elaborate on this sentence?

Thanks & Regards,
Sanket Parekh

[Muks26]

Hello @Sanket_Parekh ,

Thank you for your reply.

Actually its a 20 years of old code which is being design in a way that it will initialize both RS232 and USB once our device is bootup.

This MX250 is the part of our product and the whole code is made using the IMX data sheet.

So we are facing the problem in RS232 power consumption when our device is connected via RS232.

As per the code both RS232 and then USB will be initialized once the device is booted up and those are handled further when our FW got the handlers to detect if our device is connected via USB or RS232.

Once the handler or VBUS is detected then as if RS232 is connected then it will close all the USB related functionalities vice versa.

So to overcome we tried to return true in the USB initialization function when RS232 is connected and that reduce the power consumption which was the required one.

So the root cause is USB is getting initialize but not getting properly disabled due to which we are looking to disable USB completely instead of directly returning form beginning.

Do let me know in case of any queries.

Regards,

Mukul Parihar

[Sanket_Parekh]

Hi @Muks26 

I hope you are doing well

Please refer to the below information.

To control the power of the USB kindly refer to section 47.4.3 USB Power Control Module from the reference manual IMX25RM.pdf.

When a USB bus is idle, the transceiver can be placed in low-power (suspend) mode.

Thanks & Regards

Sanket Parekh