topic Re: How to verify LPOFF_Auto_WU worked? in Power Management

How to verify LPOFF_Auto_WU worked?

xinguang_wang — Mon, 04 Nov 2019 07:01:03 GMT

Hi,

When I using SBC FS4500, I try to verify whether the state machine swich of NORMAL MODE ->LPOFF-Auto WU->Wake-up is really worked. When in Normal mode, I sent spi by writing Mode register with LPOFF_AUTO_WU as 1 to SBC; then I watched the waveforms about the reset pin and vpre pin of SBC by oscilloscope, but it didn't happen such as from high level to low level. So I wonder to know if there are any ways to confirm the state machine switch is really worked.

Thanks a lot!

Xinguang

Re: How to verify LPOFF_Auto_WU worked?

TomasVaverka — Tue, 05 Nov 2019 11:28:06 GMT

Hi Xinguang,

Which command/sequence are you using to enter the LPOFF mode? Do you have a logic analyzer or an oscilloscope to double check the correct command was sent?

The bit LPOFF in the Mode register indicates if the device resumes from LPOFF-sleep or LPOFF_AUTO_WU mode:

The corresponding 16-bit read command is 0x2A00.

Best regards,

Tomas

Re: How to verify LPOFF_Auto_WU worked?

xinguang_wang — Wed, 06 Nov 2019 02:09:00 GMT

Hi Tomas,

Thanks for your kindly advice. In my environment, I send command to set Mode register GO_LPOFF bit as 1, and wakeup it by give IO_0 a rising edge and it really happend LPOFF as 1 which you mentioned above. However, when I send command to set Mode register LPOFF_AUTO_WU bit as 1, and do nothing, just watching whether it can happend that LPOFF is 1. Unfortunately, it doesn't work.

Best Regards,

Xinguang

Re: How to verify LPOFF_Auto_WU worked?

TomasVaverka — Wed, 06 Nov 2019 13:19:34 GMT

Hi Xinguang,

I cannot reproduce the problem you are facing.

The write command I use to set the device in LPOFF_AUTO_WU is 0xAB4D:

As you can notice, the RST pin is properly asserted low.

Then when I read the Mode register (0x2A00) I get:

... which indicates the device is back in the INIT mode resuming from LPOFF_AUTO_WU mode.

Are you using the same commands? Can you please post here your measurements?

Best regards,

Tomas

Re: How to verify LPOFF_Auto_WU worked?

xinguang_wang — Thu, 07 Nov 2019 03:09:35 GMT

Hi, Tomas

Thank you very much, I checked my code, and found that when I send command to set SBC in LPOFF_AUTO_WU, there will send command to set SBC in GO_LPOFF as well due to my code has some bug. When I fix it, it's OK.

Best regards!

Xinguang

Re: How to verify LPOFF_Auto_WU worked?

TomasVaverka — Thu, 07 Nov 2019 08:17:18 GMT

Hi Xinguang,

OK, glad to hear it is working now after fixing that bug in your code.

Best regards,

Tomas