Part 2: GPIO meets LED

ben62014-04-21

F9-Microkernel App Development

Agenda

• Why we have to know GPIO?• What’s GPIO?• How to use GPIO?

F9

Why we have to know GPIO?

Basis of external hardware control

GPIO (General-purpose input/output)

Storagedevices

NICs Buttons LED …

Agenda

• Why we have to know GPIO?• What’s GPIO?– F9 GPIO API for basic app– Code reading about F9 GPIO Hooks

• How to use GPIO?

F9

What’s GPIO?

• GPIO -- General-purpose input/output– Generic pin on a chip whose behavior

can be controlled by the user at run time

– Support DMA (Direct Memory Access) control

STM32F407VGT6 GPIOx

GPIO input

• Floating: unknown voltage input stage• Pull-up: connect to high voltage• Pull-down: connected to ground• Non-analog mode: input data register (GPIO_IDR)

Memory Devices

gpio_input_bit(port, pin){

if (*GPIO_IDR(port) & (1 << pin))return 1;

return 0;}

GPIO output

• push-pull with pull-up/pull-down• open-drain with pull-up/pull-down• Non-analog mode, output data register (GPIO_ODR)

Memory Devices

*GPIO_ODR(GPIOA) |= (1 << pin);

Agenda

• Why we have to know GPIO?• What’s GPIO?– F9 GPIO API for basic app– Code reading about F9 GPIO Hooks

• How to use GPIO?

F9

PR #86 GPIO V1 implementation

Kernel part• include/thread.h• include/user-gpioer.h• kernel/ipc.c• kernel/user-gpioer.c

App part: library and app• user/apps/gpioer/main.c• user/include/gpioer.h• user/lib/io/gpioer.c

Pull request#86 https://github.com/f9micro/f9-kernel/pull/86

GPIO V2: Kernel part GPIO driver code will move to user-space because this

part violates L4 design principle

GPIO V2: How to make thread has authority to access AHB1_1DEV?

V1: F9 GPIO API for basic app

• Defined in user/include/gpioer.h• gpioer_config_output• gpioer_out

void gpioer_config_output(uint8_t port, uint8_t pin, uint8_t pupd, uint8_t speed);

void gpioer_out(uint8_t port, uint8_t pin, uint8_t action);

V1: gpioer_config_output

void gpioer_config_output(

uint8_t port, /* Ex: GPIOA, … , GPIOD, …*/

uint8_t pin, /* 0 – 15 */

uint8_t pupd, /* GPIO_PUPDR_UP */

uint8_t speed /* GPIO_PUPDR_UP,GPIO_OSPEEDR_50M */

);

Wrap gpio_config_output from include/platform/stm32f4/gpio.h

GPIO Output Type

#define GPIO_OTYPER_PP (uint32_t (0x0) /* Output push-pull */

#define GPIO_OTYPER_OD (uint32_t)(0x1) /* Output open drain */

include/platform/stm32f4/registers.h

GPIO Speed

#define GPIO_OSPEEDR_2M (uint32_t) (0x0) /* Output speed 2MHz

*/

#define GPIO_OSPEEDR_25M (uint32_t) (0x1) /* Output speed 25MHz

*/

#define GPIO_OSPEEDR_50M (uint32_t) (0x2) /* Output speed 50MHz

*/

#define GPIO_OSPEEDR_100M(uint32_t) (0x3) /* Output speed

100MHz*/

include/platform/stm32f4/registers.h

V1: gpioer_out

void gpioer_out(uint8_t port,

uint8_t pin,

uint8_t action /* GPIO_HIGH or GPIO_LOW */

);

Wrap gpio_out_high and gpio_out_low from include/platform/stm32f4/gpio.h

Agenda

• Why we have to know GPIO?• What’s GPIO?– F9 GPIO API for basic app– Code reading about F9 GPIO Hooks

• How to use GPIO?

F9

Code reading of GPIO for user part

• user/include/gpioer.h• user/lib/io/gpioer.c

Code reading about F9 GPIO Hooks

– include/thread.h– include/user-gpioer.h– kernel/build.mk– kernel/ipc.c– kernel/user-gpioer.c

Implementation of this hook by reference the THREAD_LOG printf function

Agenda

• Why we have to know GPIO?• What’s GPIO?• How to use GPIO?– First f9 GPIO app practice to control led light– Lab3: make led blinking in turns

F9

First f9 GPIO app practice to control led light

• PR86– https://github.com/f9micro/f9-kernel/pull/86

• Demo1. built-in 4 LEDs Blinking2. trigger External LED

Live Demo 1: built-in 4 LEDs Blinking

STM32F407 Built-in 4 User LEDs

LD3 (orange)LD4 (green) LD5 (red) LD6 (blue)

PD13

PD12

PD14

PD15

Live Demo 2: trigger External LED

Lab 3: LEDs blinking Rocks

Requirements– Modify LED sample to let the led in turns– Blinking interval 2 seconds

Hints: reference user/apps/gpioer/main.c

git clone https://github.com/benwei/f9-kernel.gitgit checkout 0421-gpioer

Summary: Points recall

• GPIO is the basis of external control

• What’s implementation of GPIO api for user app

• Easy to use API for gpioer for pin output control

Discussions

?

F9

References• F9 Microkernel source code and introduction

• GCC Naked Attribute

• ARM: Memory Model of Cortex M4

• Cortex™ -M4 Devices Generic User Guide pdf

• General-purpose Input/Output (GPIO)

• UM1472 User manual Discovery kit for STM32F407/417 lines

• STM32F4-Discovery 中文使用手冊