====== Alternate Functions (GPIO) ======

  * The output buffer can be enabled (open drain or push-pull).
  * The output buffer is controlled by connected peripheral.
  * The Schmitt trigger input is active.
  * The pull-up and -down resistors are active, according to [[gpio#registers|PUPDR]].
  * Input data is sampled every AHB clock.
  * Input data register holds I/O state.

\\ {{gpio_complete.svg}} \\ \\

===== Programming Instructions =====

Depending on the alternate function you have to configure the pins as:
  * [[gpio_input#programming_instructions|digital input]],
  * [[gpio_output#programming_instructions|digital output]] or
  * [[gpio_analog#programming_instructions|analog input]].
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===== Configuration Registers =====

==== GPIOx_MODER - Mode register ====

\\ {{gpio_reg_common.svg}} \\ \\

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|Pin x|10|Alternate function mode|

==== GPIOx_AFRL/H - Alternate function register (low / high) ====

\\ {{gpio_reg_afrl.svg}} \\ \\
\\ {{gpio_reg_afrh.svg}} \\ \\

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|Pin x|0000|AF0: RTC, MCO, Tamper, SWJ, Trace|
|:::|0001|AF1: Timer 1, [[timer2_5|Timer 2]]|
|:::|0010|AF2: [[timer2_5|Timer 3..5]]|
|:::|0011|AF3: Timer 8..11|
|:::|0100|AF4: I²C 1..3|
|:::|0101|AF5: SPI 1..6|
|:::|0110|AF6: SPI 2/3, SAI 1|
|:::|0111|AF7: SPI 3, USART 1..3|
|:::|1000|AF8: USART 6, UART 4/5/7/8|
|:::|1001|AF9: CAN 1/2, Timer 12..14, LCD|
|:::|1010|AF10: USB OTG HS/FS|
|:::|1011|AF11: Ethernet|
|:::|1100|AF12: FMC, SDIO, USB OTG FS|
|:::|1101|AF13: DCMI|
|:::|1110|AF14: LCD|
|:::|1111|AF15: Event Out|

==== GPIOx_PUPDR - GPIO port pull-up / pull-down register ====

\\ {{gpio_reg_common.svg}} \\ \\

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|Pin x|00|No pull-up, pull-down (reset state)|
|:::|01|Pull-up|
|:::|10|Pull-down|
|:::|11|Reserved|

==== GPIOx_OTYPER - Port output type register ====

\\ {{gpio_reg_otyper.svg}} \\ \\

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|Pin x|0|Output type: push-pull (reset state)|
|:::|1|Output type: open-drain|

==== GPIOx_OSPEEDR - Port output speed register ====

\\ {{gpio_reg_common.svg}} \\ \\

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|Pin x|00|Speed: 2 MHz (reset state)|
|:::|01|Speed: 10 MHz|
|:::|10|Speed: 50 MHz|
|:::|11|Speed: 100 MHz|