STM32F407VGXT DIscovery GPIO state at start_up

[Bruno Brentegani]

Posted on April 20, 2018 at 14:47

Hi all,

I'm using stm32f4 discovery with HAL drivers to realize a Synchronous BOOST DCDC.

When the system is turn on, the gpio PE8 and PE9 configured as PWM pins of TIM1,(in particular PWMOUT_CH1 & PWMOUT_CH1N) goes in SET state and for a  few milliseconds keep the mos of the converter in ON state causing a little initial short circuit.

At startup PE8 and PE9 are in high impedance state?

If so,can i avoid this issue with a 100k pull down resistors?

There are software solutions to this problem?

Best regards

Bruno

[Tesla DeLorean]

Posted on April 20, 2018 at 15:06

>>There are software solutions to this problem?

Not on the F4 series, best to define default high-low states with external pull up/down resistors. Placing code to program the GPIO in the Reset_Handler can reduce the time they are in undesirable states as subsequent code will spin up clocks and PLLs.

I think one of the L4 or newer families provides a means of defining pin states at startup

[Bruno Brentegani]

Posted on April 20, 2018 at 15:09

Thanks Clive one