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Damaged? 2.5V at PA4 in Reset state (STM32F446VET)

Question asked by Miro Mico on Jun 29, 2017
Latest reply on Jun 29, 2017 by waclawek.jan

Hi,

Im trying to optimize LowPower current consumption of a custom board my hardware guys have made arround a 100pin LQFP STM32F446VET. Currently I fight to find the source of a faulty voltage at GPIO PA4 (Pin 29 with this housing). I desoldered the pin from the board that it is not connected to anything. The pin outputs a voltage of 2.5V after reset and in GPIO's reset state. When I configure the pin as a normal GPIO I can output a 0 (0 Volts). But as soon as I call HALs HAL_GPIO_DeInit() the 2.5 Volt output re-appears. When I measure the current from this 2.5 Volts to ground I see 240µA on my ampmeter. This is the equivalent of a 10 kOhm impendance. According to the datasheet this pin has alternate functions like DAC_OUT1 and USB_OTG_HS_SOF. But all GPIOx->AFR[] are set to 0. Same behavior on a second identical board.

Is it possible that I damaged the pin by a connected 8 Ohm @ 1 kHz loudspeaker (induced reverse or high voltage by the speakers high inductance)?

Any idea, what is going wrong with my device?

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