Peripheral firmware examples description

AN4157

10/24

Doc ID 023629 Rev 1

3.8

FPU example

3.8.1

Purpose

This example provides information on FPU instructions.

3.8.2

Description

This example shows the benefits of using the STM32F3 FPU. It computes simple

mathematical and standard operations with floating point input numbers.

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The time spent for the calculation of these operations wheen FPU is enabled is about

30 µs while it is about 50 µs when FPU is disabled. The gain is consequently of 40% .

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In term of code size, using the IAR toolchain, the gain is about 15%:

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FPU enabled: 4264 bytes of Flash memory

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FPU disabled: 4920 bytes of Flash memory

3.9

GPIO toggle example

3.9.1

Purpose

This example shows how to use the GPIO port bit set/reset registers (BSRR and BRR) for

I/O toggling.

3.9.2

Description

In this example:

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GPIOE clock is enabled.

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GPIOE pins 14 and 15 are configured.

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In a while loop, the ODR14 and ODR15 bits are set in the GPIOE output data register

(ODR) by setting the corresponding bits in the port bit set/reset register (BSRR). Then

the ODR14 and ODR15 bits are reset in the GPIOC output data register (ODR) by

setting the corresponding bits in the port bit reset register (BRR).

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A delay is inserted between setting and resetting the GPIOE ODR14 and ODR15 bits.

When the program is executed, the two LEDs, LED7 and LED10, are turned ON then OFF in

an infinite loop. The duration between the ON and OFF states corresponds to the inserted

delay.

Note:

Connect the oscilloscope to the pins PE14 and PE15.