STOP Mode EXTI does not work on STM32L031 nucleo board

[Michel COURTITARAT]

Posted on September 03, 2017 at 11:43

Hi,

I am trying to test the low power modes on the STM32L031 Nucleo board.

I used the example of STM32Cube_FW_L0_V1.9.0 (STM32L031K6-Nucleo32\STM32Cube_FW_L0_V1.9.0\Projects\STM32L031K6-Nucleo\Examples\PWR\PWR_STOP) iwth IAR compiler.

Actually, le code works when the board is powered by le USB cable or the Vin pin.

But if the board is powered by the 5V pin or 3V3 pin, the code does not work.

The expected behavior is : wake up from STOP mode by a falling edge on PA.12, then blinking the led on PB.3 and return to STOP mode.

The PA.12 is configured with the pull up internal resistor.

The voltage on pin PA.12 shall be 3V3 due to the pull up resistor. It is the right when the board is powered by USB or Vin but the voltage on PA.12 drops around 0V when the board is powered by 5V or 3V3 pin.

Anybody has an explanation of the trouble ?

#stop-mode #stm32l031 #exti #nucleo-l031 #stm32l0-exti

[Brian TIDAL]

Posted on September 04, 2017 at 21:37

Hi Michel,

can you elaborate regarding 'if the board is powered by the 5V pin or 3V3 pin, the code does not work.'? Do you mean, the board does not boot up or do you mean, the board is booting but the wakeup from Stop mode is not working?

Can you make sure to follow the recommended solder bridge (SB) configuration in

http://www.st.com/content/ccc/resource/technical/document/user_manual/e3/0e/88/05/e8/74/43/a0/DM00231744.pdf/files/DM00231744.pdf/jcr:content/translations/en.DM00231744.pdf

for the various power supply configurations (e.g. SB14 & SB9 OFF for 3V3)? Also, can you make sure your 5V and 3V3 power supply is able to provide the requested current?

Regards

Bruno

[Michel COURTITARAT]

Posted on September 05, 2017 at 00:00

Hi Bruno,

Thanks for your answer.

Here are the following checks :

1 : The board is powered by USB cable (SB14 & SB9 ON; SB1 OFF). The board boots properly and the wake up after STOP mode works. There is no problem about current consumption.

2 : The board is powered by Vin pin @ 7V (SB14 & SB9 ON; SB1 OFF). Red LED LD2 = ON, LED LD1 flash red at around 1Hz.The board boots properly and the wake up after STOP mode works. There is no problem about current consumption.

3 : The board is powered by 5V pin @ 5V (SB14 & SB9 ON; SB1 OFF). Red LED LD2 = ON, LED LD1 OFF.The board does not boot. The current consumption is less than 4 mA. The voltage pin RST is 1.28V. ther is no problem about the power supply.

Do I to remove SB9 in that case ?

4 : The board is powered by 3V6 though a schottky diode to pin @ 3V3.

Before your answer, the straps were as : SB14 OFF; SB9 ON; SB1 OFF

I have remove SB9 and now the board woks correctly. Red LED LD2 = OFF, LED LD1 OFF. The board boots properly and the wake up after STOP mode works.

The problem was due to SB9.

Best regards

[Brian TIDAL]

Posted on September 05, 2017 at 08:15

Hi Michel,

SB9 controls whether NRST is controlled by ST-LINK.

When using 5V power supply:

• if you connect the USB cable after you power the board then the ST-LINK will be able to control the NRST signal (see 6.4.2 in

  http://www.st.com/content/ccc/resource/technical/document/user_manual/e3/0e/88/05/e8/74/43/a0/DM00231744.pdf/files/DM00231744.pdf/jcr:content/translations/en.DM00231744.pdf

  )
• If you do not connect the USB cable then you need to remove SB9 otherwise the NRST will prevent the board to boot (see table 7 in

  http://www.st.com/content/ccc/resource/technical/document/user_manual/e3/0e/88/05/e8/74/43/a0/DM00231744.pdf/files/DM00231744.pdf/jcr:content/translations/en.DM00231744.pdf

  ).

Regards

Bruno