Slides for Sharing at JuluOSDev 04/21

1. Part 2: GPIO meets LED
ben6
2014-04-21
F9-Microkernel App Development

2. Agenda
• Why we have to know GPIO?
• What’s GPIO?
• How to use GPIO?
F9

3. Why we have to know GPIO?
Basis of external hardware control
GPIO (General-purpose input/output)
Storage
devices
NICs Buttons LED
…

4. 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

5. 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

6. STM32F407VGT6 GPIOx

7. 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;
}

8. 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);

9. 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

10. 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?

11. 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);

12. 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

13. 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

14. 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

15. 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

16. 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

17. Code reading of GPIO for user part
• user/include/gpioer.h
• user/lib/io/gpioer.c

18. 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

19. 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

20. First f9 GPIO app practice to control
led light
• PR86
– https://github.com/f9micro/f9-kernel/pull/86
• Demo
1. built-in 4 LEDs Blinking
2. trigger External LED

21. Live Demo 1: built-in 4 LEDs Blinking

22. STM32F407 Built-in 4 User LEDs
LD3 (orange)
LD4 (green)
LD5 (red)
LD6 (blue)
PD13
PD12
PD14
PD15

23. Live Demo 2: trigger External LED

24. 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.git
git checkout 0421-gpioer

25. 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

26. Discussions
?
F9

27. 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