STM32L4 power consumption reduction

[lorant124]

Hi,

I've created a PCB with an STM32L4x6 microcontroller and several peripherals, mainly I2C. I want to sample data at 512Hz using the internal ADC. The original plan was to configure the ADC  with DMA and a timer, I'd put the MCU into other low-power states and wake up to DMA interrupt. However, I've encountered a problem in implementing this. Using 'Sleep' mode with RTC wake-up works, but power consumption decrease only with ~300uA, which is not ideal. The 'STOPX' mode doesn't work with the ADC.

I've tried reducing the clock frequency; currently, the MCU is running at 4MHz because I perform FFT calculations and other tasks after sampling, which would be too time-consuming at a lower clock speed within a 1-second timeframe.

I thought about increasing the clock speed during calculations and then reducing it, but I'm not sure how to execute this without affecting the ADC, DMA, and timer.

My question is, how can I efficiently achieve the following:

1. ADC sampling at 512Hz DMA+Timer?
2. Modifying the clock frequency while the ADC is sampling.
3. Any other suggestions for improving energy efficiency in this setup?

Thank you for any help :)
Best regards,

Lorant 

[jiangfan]

AN4746 (Optimizing power and performance with STM32L4 and STM32L4+ Series
microcontrollers) should be a good document deserved to read for your question.

Optimizing power and performance with STM32L4 and STM32L4+ Series microcontrollers - Application note

[jiangfan]

You may also read the DMA presentation:

stm32l4_system_dma.pdf

[Piranha]

Get rid of the HAL/Cube broken bloatware and software will run faster. Less CPU time also means less power in active mode and more time spent in low-power modes. And by the way, the code and data size also has a significant impact on execution speed, because the less the size, the less cache (ART) misses.