Interface Description
The GPIO (General Purpose the Input / the Output) GPIOs i.e., hereinafter referred to as I / O ports. I / O ports provide input, output or interrupt the three types of functions embedded field is the most common and basic hardware.
GPIO in the introduction SylixOS in front of the driver how to write, we start to understand how to call the next application layer is the GPIO, the first will be followed by, in order to better drive to develop and test. For the application layer, GPIO is /dev/gpiofda device file directory through standard file functions can operate. In view of the inherent characteristics of GPIO used, and to simplify the interface, SylixOS package further standard functions obtained three simple file operation GPIO function, still use file closing closefunction.
/*********************************************************************************************************
** 函数名称: gpiofd
** 功能描述: 打开 gpiofd 文件
** 输 入 : gpio gpio 号
** flags 打开标志 GFD_CLOEXEC / GFD_NONBLOCK
** gpio_flags gpio 属性标志
** 输 出 : gpiofd 文件描述符
*********************************************************************************************************/
int gpiofd(unsigned int gpio, int flags, int gpio_flags);
/*********************************************************************************************************
** 函数名称: gpiofd_read
** 功能描述: 读取 gpiofd 文件
** 输 入 : fd 文件描述符
** value 读取缓冲
** 输 出 : 0 : 成功 -1 : 失败
*********************************************************************************************************/
int gpiofd_read(int fd, uint8_t *value);
/*********************************************************************************************************
** 函数名称: gpiofd_write
** 功能描述: 写 gpiofd 文件
** 输 入 : fd 文件描述符
** value 写入数据
** 输 出 : 0 : 成功 -1 : 失败
*********************************************************************************************************/
int gpiofd_write(int fd, uint8_t value);
- Use these three operations functions you will need to include the header file
<sys/gpiofd.h>. - Function is
gpiofdused to open a GPIO device file, but the argumentgpiois not a file name but figures. To improve readability GPIO figures can be represented by the macro definition, another blog " SylixOS GPIO number in the macro definition ," and explained in detail to achieve. - Parameter
flagsandopenthe second parameter function similar meaning, i.e., may beO_RDONLY,O_RDWR,O_RDWRlike, but are in fact in accordance with the internalO_RDWRparameters of the operation; - Parameters
gpio_flagsassociated with the identification GPIO features, which may be identified by a combination of a plurality of bits. Refer to the following table:
| Bit identifier name | Explanation |
|---|---|
| GPIO_FLAG_DIR_OUT | To set the output GPIO |
| GPIO_FLAG_DIR_IN | Set GPIO input function |
| GPIO_FLAG_IN | The same GPIO_FLAG_DIR_IN |
| GPIO_FLAG_OUT_INIT_LOW | GPIO function to set the output, while output low initialization |
| GPIO_FLAG_OUT_INIT_HIGH | GPIO output is set, and outputs a high level to initialize |
| GPIO_FLAG_OPEN_DRAIN | Set GPIO output drain output mode |
| GPIO_FLAG_OPEN_SOURCE | GPIO output is provided to a source output mode |
| GPIO_FLAG_PULL_DEFAULT | Using the default pull-up / pull-down mode |
| GPIO_FLAG_PULL_UP | A pullup resistor pattern |
| GPIO_FLAG_PULL_DOWN | Mode using pull-down resistor |
| GPIO_FLAG_PULL_DISABLE | Prohibit pull-up / pull-down mode |
| GPIO_FLAG_TRIG_FALL | Set GPIO interrupt function, and the falling edge-triggered interrupts |
| GPIO_FLAG_TRIG_RISE | Set GPIO interrupt function, and Interrupt on rising edge |
| GPIO_FLAG_TRIG_LEVEL | Set GPIO interrupt function, and level-triggered interrupts |
To use the GPIO interrupt function, first set it when you open the device gpio_flagsparameters in response to the interrupt mode. Secondly because GPIO devices are non-blocking file read and write, but also with selectfunction blocking and timeout function. When a GPIO with interrupt function generates an interrupt, the kernel wakes up all waiting threads by calling the select state of the GPIO readable file descriptor, notification thread interrupt is generated. When the select returns properly, threading corresponding transaction, which is similar to the completion of a service interruption.
Note that when using the GPIO_FLAG_TRIG_LEVEtime identified, we use only GPIO_FLAG_TRIG_FALLthe GPIO_FLAG_TRIG_RISEuse of a combination with, respectively, low and high level triggering. When not used GPIO_FLAG_TRIG_LEVE, we can GPIO_FLAG_TRIG_FALLand GPIO_FLAG_TRIG_RISEin combination represent a double-edge triggered.
Complete routine
/*********************************************************************************************************
**
** 中国软件开源组织
**
** 嵌入式实时操作系统
**
** SylixOS(TM) LW : long wing
**
** Copyright All Rights Reserved
**
**--------------文件信息--------------------------------------------------------------------------------
**
** 文 件 名: gpioExample.c
**
** 创 建 人: Hou.JinYu (侯进宇)
**
** 文件创建日期: 2017 年 12 月 13 日
**
** 描 述: gpio 例程,针对NXP i.MX-RT1050 EVK开发版。
** 因为连接板载 LED01 的引脚同时也连接了 enet 的复位脚，硬件冲突故不能使用。
** LED02 只是一个空闲的gpio（为J22.7）,需要用户连接LED或万用表来检测电平变化。
*********************************************************************************************************/
#include <stdio.h>
#include <sys/select.h>
#include <sys/gpiofd.h>
#include "gpio/gpio.h"
#include "config.h"
/*********************************************************************************************************
引脚宏定义
********************************************************************************************************/
#define KEY08 GPIO_E_00 /* GPIO5--00 */
#define LED01 GPIO_A_09 /* GPIO1--09 */
#define LED02 GPIO_A_18 /* GPIO1--18 */
/*********************************************************************************************************
** 函数名称: gpioExample1
** 功能描述: gpio 轮询读取例程
** 输 入: NONE
** 输 出: ERROR_CODE
*********************************************************************************************************/
static int gpioExample1 (void)
{
int keyfd;
int ledfd;
uint8_t value;
printf("Gpio poll example. Waiting press the key SW8.\n");
keyfd = gpiofd(KEY08, O_RDWR, GPIO_FLAG_IN); /* 打开 KEY 的 GPIO 文件 */
if (keyfd < 0) {
printf("open gpio %d failed!\n", KEY08);
return (PX_ERROR);
}
ledfd = gpiofd(LED02, O_RDWR, GPIO_FLAG_OUT_INIT_LOW); /* 打开 LED 的 GPIO 文件 */
if (ledfd < 0) {
printf("open gpio %d failed!\n", LED02);
close(keyfd);
return (PX_ERROR);
}
while (1) {
gpiofd_read(keyfd, &value); /* 读取当前按键值 */
printf("The key value = %d\n", value);
gpiofd_write(ledfd, value & 0x01); /* 设置LED引脚输出 */
sleep(1);
}
close(keyfd); /* 关闭 KEY 的 GPIO 文件 */
close(ledfd); /* 关闭 LED 的 GPIO 文件 */
return (ERROR_NONE);
}
SHELL_CMD_REG("gpioExample1", gpioExample1);
/*********************************************************************************************************
** 函数名称: gpioExample2
** 功能描述: gpio 中断例程
** 输 入: NONE
** 输 出: ERROR_CODE
*********************************************************************************************************/
static int gpioExample2 (void)
{
int n = 0;
fd_set fdset;
int ret;
int keyfd;
int ledfd;
printf("Gpio interrupt example. Waiting press the key SW8.\n");
keyfd = gpiofd(KEY08, O_RDWR, GPIO_FLAG_TRIG_FALL); /* 打开 KEY 的 GPIO 文件 */
if (keyfd < 0) {
printf("open gpio %d failed!\n", KEY08);
return (PX_ERROR);
}
ledfd = gpiofd(LED02, O_RDWR, GPIO_FLAG_OUT_INIT_LOW); /* 打开 LED 的 GPIO 文件 */
if (ledfd < 0) {
printf("open gpio %d failed!\n", LED02);
close(keyfd);
return (PX_ERROR);
}
FD_ZERO(&fdset);
while (1) {
FD_SET(keyfd, &fdset);
ret = select(keyfd + 1, &fdset, NULL, NULL, NULL); /* 调用 select 等待按键被按下 */
if (ret == 1) {
printf("The key effective, n = %d\n", n++);
gpiofd_write(ledfd, n & 0x01); /* 设置LED引脚输出 */
} else if (ret < 0) {
printf("select error!\n");
break;
}
}
close(keyfd); /* 关闭 KEY 的 GPIO 文件 */
close(ledfd); /* 关闭 LED 的 GPIO 文件 */
return (ERROR_NONE);
}
SHELL_CMD_REG("gpioExample2", gpioExample2);
/*********************************************************************************************************
END
*********************************************************************************************************/
Experimental Procedure
1. The input command gpioExample1, to start a query routine gpio;
2. The console output once per second key value, press the button to see the key value becomes zero. LED pin also changes the key state is changed in accordance with.
3. The system reset input command gpioExample2to start the interrupt routine gpio;
4. Press the button triggers the falling edge of the interrupt, so that a wake-select function. Each press of the push button will print out the number, and the LED changes again.
