Ole Eberson

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6 years ago.

Which sleep mode to use (F446RE)

Hi,

We're trying to find the best option to run F446REs long term on a battery. They are taking a measurement every 10 minutes or so and send it to a LoRa gateway. The problem is that they are consuming way too much power while idling around for the 10 minutes. I have tried multiple things to get the power consumption down, but can't seem to find a satisfying solution. The closest I got was using HAL_PWR_EnterSTANDBYMode(). The Idd goes down to a few uA. But when measuring the current the whole board takes from the battery it is still around 50mA, which is way too high.
I am grateful for any thoughts on this or for helpful links on how to properly use the sleep() function, since I had a lot of problems with it (not waking up, not even going to sleep and more).

Ole

1 Answer

Ralph Fulchiero
6 years ago.

Hi Ole,

Are you using the Mbed LPTICKER configuration option - this should be enabled by default for recent versions of Mbed. You can try to incorporate the TICKLESS feature (added in v5.8) which should help reduce power consumption if your application can work with it.

Tickless is described here:

To really help you though we'll need to gather some additional information. Please let us know:

  • What version of Mbed are you using?
  • How are you performing the periodic wakeup?
  • What peripherals/IO need to be kept on during the 10 minutes between readings/transmissions?
  • What clock source are you using?
  • Have you made any modifications to the Mbed configuration through the JSON files?
  • Is this a custom board or a 3rd party board?

Regards,

Ralph, Team Mbed

Hi Ralph,

thanks a lot for your answer. I will look into the whole tickless thing. The video might be helpful, too. I hope I will find time (and internet connection) tonight to watch it.

My version of mbed-os is up to date (5.10.2).

I got the best results using this. It uses a RTC wake up timer to wake up . Nothing needs to be kept on during the 10 minutes. To be honest, I'm not sure about the clock source. I guess for the wakeup only the RTC is needed, correct? I have not changed the JSON files.

It is an STM32 Nucleo-F446RE board.

Ole

posted by Ole Eberson 30 Oct 2018