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maryam magdy
maryam magdy
Associate III
February 6, 2019
Solved

Lowest power mode for accelerometer application in STM32L4 ?

  • February 6, 2019
  • 5 replies
  • 2106 views

Hi, I wanna use the lowest power mode possible for my stm32l432kc. I want MCU to wakeup on accelerometer motion (which is possible since the accel generate interrupt on motion). I've read in MCU appnopte AN4621(page 13) that i2c is detected only in stop mode and that it generate a wakeup on i2c address detection (if I understand it correctly). But as I explained this is not what I want. I wonder if I can use shutdown or standby?

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Best answer by After Forever

It depends on the accelerometer model and your schematics. Can it remain powered on and working while the MCU is in standby/shutdown mode? Does it send its wakeup event as a simple IO rising/falling edge which can be simply connected to MCU's WakeUp pin, or does it use the I2C as you think? I don't think it uses I2C to send an event (I've never seen an accelerometer which is I2C master rather than slave).

5 replies

Mohamed Aymen HZAMI
Mohamed Aymen HZAMI
ST Employee
February 6, 2019

Hello Maryam,

For further information about the STM32L4 power mode you can refer to this training online session :

https://www.st.com/content/st_com/en/support/learning/stm32-education/stm32l4-online-training.html

Best Regards,

Mohamed Aymen.

maryam magdy
maryam magdyAuthor
Associate III
February 7, 2019

@Community member​  can you please advise?

After Forever
After Forever
Senior III
February 7, 2019

If your accelerometer can generate an IO event then use the WKUP pin to catch the event and wake up from the standby/shutdown mode.

Read the reference manual (RM0394), sections 5.3.9 (Standby mode) and 5.3.10 (Shutdown mode).

maryam magdy
maryam magdyAuthor
Associate III
February 7, 2019

So you think that the accelerometer would be able to detect motion while the MCU is in shutdown/standby mode and wakeup the MCU? Because as I mentioned in the post and what I could understand is that the accel won't be able to work unless the MCU is at least in the stop2 mode.

After Forever
After ForeverBest answer
Senior III
February 7, 2019

It depends on the accelerometer model and your schematics. Can it remain powered on and working while the MCU is in standby/shutdown mode? Does it send its wakeup event as a simple IO rising/falling edge which can be simply connected to MCU's WakeUp pin, or does it use the I2C as you think? I don't think it uses I2C to send an event (I've never seen an accelerometer which is I2C master rather than slave).

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