AN4088 datasheet(46/71 Pages) STMICROELECTRONICS

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Firmware migration using the library

AN4088

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DocID023072 Rev 3

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; /* None, Pull-up or pull-

down */

GPIO_Init(GPIOy, &GPIO_InitStructure);

4.5.3

Analog mode

The example below shows how to configure an I/O in analog mode (for example, an ADC or

DAC channel) in STM32F1 series:

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_x;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;

GPIO_Init(GPIOy, &GPIO_InitStructure);

In STM32F0 series, you have to update this code as follows:

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_x ;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;

GPIO_Init(GPIOy, &GPIO_InitStructure);

4.5.4

Alternate function mode

In STM32F1 series

The configuration to use an I/O as an alternate function depends on the peripheral

mode used; for example, the USART Tx pin should be configured as an alternate

function push-pull while the USART Rx pin should be configured as an input floating or

an input pull-up.

To optimize the number of peripheral I/O functions for different device packages, it is

possible, by software, to remap some alternate functions to other pins. For example,

the USART2_RX pin can be mapped on PA3 (default remap) or PD6 (by software

remap).

In STM32F0 series

Whatever the peripheral mode used, the I/O must be configured as an alternate

function, then the system can use the I/O in the proper way (input or output).

The I/O pins are connected to on-board peripherals/modules through a multiplexer that

allows only one peripheral alternate function to be connected to an I/O pin at a time. In

this way, there can be no conflict between peripherals sharing the same I/O pin. Each

I/O pin has a multiplexer with sixteen alternate function inputs (AF0 to AF15) that can

be configured through the GPIO_PinAFConfig () function:

–

After reset, all I/Os are connected to the system alternate function 0 (AF0)

–

The peripherals’ alternate functions are mapped by configuring AF1 to AF7.

In addition to this flexible I/O multiplexing architecture, each peripheral has alternate

functions mapped onto different I/O pins to optimize the number of peripheral I/O

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