Vybrid Sample Source Code - Low Power

[dachancellor]

I am using the Vybrid Tower Kit and attempting to take some power measurements.

I have loaded the low-power example that steps through a range of modes and samples the ADC.

RUN, LPRUN, STOP, etc.

However, I cannot get it to go into LPSTOPx.

The source code mentions that the M4 may be the cause.

I have tested the example with and without the M4 running.

In both cases, the processor does not appear to enter LPSTOP.

Is there some further configuration that must be done to allow LPSTOP ?

V/r,

Chandler

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[jiri-b36968]

Hello Chandler,

to enter stop mode all enabled cores have to call WFI. So if M4 core is enabled in debugger or in the code call also here WFI. If M4 core is not enabled then it is not necessary.

Do you use TWR-Vf65 rev.H ?

Which code you use? Vybrid sample code freescale.com/vybrid ( http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=TWR-VF65GS10&fpsp=1&tab=Design_Tools_...) ?

/Jiri

[dachancellor]

Hi Jiri,

It is the low power sample contained on the page you linked (from the VYBRID_SAMPLE_CODE_SBCH.exe).

It is a TWR-VF65 board, and there are 2 stickers on bottom.  One says REV H and one says REV J1.

We have tried running the code both with and without the M4 enabled.

There is a start_m4 function called from the sample code.  We ran with and without this function called.

Additionally, we've ensured the debugger does not start the M4 clock.

In all cases, we have no success entering any LPStopx mode.

Any ideas are much appreciated !

V/r,

Chandler

[jiri-b36968]

Hello Chandler,

CM4 can be enabled in DS-5 debugger - please check. Sample code includes identification of each core, which is relocated to separate UART. So when you run the code you see something on console for each core and if disable (not enable) CM4 core there is not anything for UART dedicated for CM4?

Attached is little bit improved sample code.

This was working for sure - if not we have to go deeper.

/Jiri

[dachancellor]

Hi Jiri,

I was able to get the low power axf converted to a bin file and loaded via U-Boot from the SD Card.

With that, and some minor modifications to the low power code...I was able to get it to LPSTOP1, ~200uA at the 3v3.

However, it doesn't always work...so there's still something flaky going on.

I'm not sure if U-Boot is the issue, or if I'm properly converting to a bin, and jumping to the correct address in the program.

Are there any guides or examples for how to handle this correctly ?

Thanks

[jiri-b36968]

Hello Chandler,

Unfortunately no other official code available then VybridSC. You can check MQX or community threads.

Low power demo is quite complex - remove all not necessary options.

On rev.H (which you have) are added missing pull-ups on wake-up pins - so it should work correctly.

/Jiri

[dachancellor]

Hi Jiri,

Thanks for the updated code.

We've spent the last week poking around with the newer code, but we're seeing the same results.

We've been unable to reach LPStop.

Measuring current and stepping through the code, the lowest current we see is when the PLLs are turned off.

It doesn't go lower when the WFI is called to enter LPStop, so we're pretty certain something is keeping the processor on.

Any ideas what may be the issue ?

Is there a correct way to load the program in to run ?

I know in the past I've experience issues with the debugger preventing low power modes.

Is there a guide for creating a binary that can be loaded from the SD card or something like that ?

Thanks,

Chandler