====== GPIO Port A..H ======

The STM32F429ZI has a total of 8 GPIO ports (A..H). Each port offers 16 I/O pins (except port H, which offers only 2). Each pin can individually be configured as input, output or be connected to one of the other peripherals (alternate function). 

{{ gpio_complete.svg }}

===== Features =====

  * Up to 114 I/O ports.
  * Output states: push-pull or open-drain + pull-up/-down.
  * Input states: floating, pull-up/-down or analog.
  * Speed selection for each I/O.
  * Up to 90 MHz toggeling speed.

===== GPIO Register Description =====

{{:stm32:register_descriptions:gpio_registers_st_rm.pdf|}} 

Extract from ST Reference Manual

===== Functions =====

After reset most of the pins are configured as floating general purpose input. The ones that are not, are used for the debug/programming interface:

|< 100% 10em >|
|Port A.15|JTDI, JTAG Data Input|pull-up|
|Port A.14|JTCK/SWCLK, JTAG / Serial Wire Clock|pull-down|
|Port A.13|JTMS/SWDAT, JTAG Mode Select / Serial Wire Data (Input/Output)|pull-up|
|Port B.4|NJTRST, JTAG Reset (Inverted)|pull-up|
|Port B.3|JTDO, JTAG Data Output|floating|

These modes are available per pin:

  * [[gpio_input|Input mode]] for reading external signals.
  * [[gpio_output|Output mode]] for outputing signals.
  * [[gpio_analog|Analog mode]] for [[adc|AD- / DA-conversion]].
  * [[gpio_alternate|Alternate function mode]] for various peripherals, eg. [[timer_compare|PWM]], [[usart|USART]].