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mbed os是ARM以C++为主要开发语言的RTOS,提供Mbed Studio集成开发环境,支持很多开发板,屏蔽了底层驱动,给应用层提供统一的接口。楼主抽空体验了基于mbed os平台使用C++开发驱动程序, 测试使用stm32wb55驱动I2C接口的CO2、TVOC传感器SGP30,使用GPIO模拟I2C和硬件I2C两种方法实现。使用C++更加直观,可读性更强,封装性更强,更方便维护,尤其在多人协同开发优势更明显。
首先设计一个基类GPIO_I2C ,私有成员变量_scl_io和_sda_io用于操作GPIO,提供GPIO输入输出设置、上下拉设置、高低电平输出、读取输入电平等基本操作方法;然后设计一个SGP30类,继承自GPIO_I2C,提供SGP30初始化、序列号获取、传感器数据获取、软复位等方法。关于SGP30的寄存器和驱动时序本帖不再赘述,https://bbs.21ic.com/icview-3273394-1-1.html中有详细描述。头文件设计如下:
- #ifndef MBED_SGP30_H
-
- #define MBED_SGP30_H
-
-
-
- #include "mbed.h"
-
-
-
- //启用硬件I2C去掉注释,启用GPIO软件模拟模拟I2C保留注释
-
- //#define HARD_I2C 1
-
-
-
- //SGP30 I2C设备地址
-
- #define SGP30_ADDR 0x58
-
- //SGP30 I2C写地址
-
- #define SGP30_ADDR_WRITE (SGP30_ADDR << 1) // 0xb0
-
- //SGP30 I2C读地址
-
- #define SGP30_ADDR_READ ((SGP30_ADDR << 1) + 1) // 0xb1
-
- /* SGP30初始化空气质量测量寄存器 */
-
- #deSGP30fine SGP30_CMD_INIT_AIR_QUALITY 0x2003
-
- /* 开始空气质量测量寄存器 */
-
- #define SGP30_CMD_MEASURE_AIR_QUALITY 0x2008
-
- /* SGP30获取串号寄存器 */
-
- #define SGP30_CMD_GET_SERIAL_ID 0X3682
-
-
-
- //GPIO基类
-
- class GPIO_I2C {
-
- //公有成员
-
- public:
-
- GPIO_I2C(PinName scl, PinName sda);//构造函数
-
- ~GPIO_I2C();//析构函数
-
- void SDA_SET_OUT();//设置SDA输出模式方法
-
- void SDA_SET_IN();//设置SDA输入模式方法
-
- void SGP30_SCK_L();//设置SCL输出低电平方法
-
- void SGP30_SCK_H();//设置SCL输出高电平方法
-
- void SGP30_SDA_L();//设置SDA输出低电平方法
-
- void SGP30_SDA_H();//设置SDA输出高电平方法
-
- int SGP30_READ_SDA();//读取SDA输入电平方法
-
- void sgp30_delay_us(uint32_t us);//延时微秒方法
-
- void sgp30_delay_ms(uint32_t nms);//延时毫秒方法
-
- void IIC_Start(void);//I2C开始信号方法
-
- void IIC_Stop(void);//I2C停止信号方法
-
- uint8_t IIC_Wait_Ack(void);//I2C等待应答方法
-
- void IIC_Ack(void);//I2C应答方法
-
- void IIC_NAck(void);//I2C无应答方法
-
- void IIC_Send_Byte(uint8_t txd);//I2C发送1字节数据方法
-
- uint8_t IIC_Read_Byte(uint8_t ack);//I2C接收1字节数据方法
-
- //私有成员
-
- private:
-
- DigitalOut *_scl_io;//scl操作对象指针成员变量
-
- DigitalInOut *_sda_io;//sda操作对象指针成员变量
-
- };
-
-
-
- //SGP30对象继承自GPIO_I2C对象
-
- class SGP30 : GPIO_I2C {
-
-
-
- public:
-
- SGP30(PinName scl, PinName sda);//构造函数
-
- ~SGP30();//析构函数
-
-
-
- int sgp30_init(void);//SGP30初始化方法
-
- int sgp30_read(uint16_t *CO2, uint16_t *TVOC);//SGP30读取传感器数据方法
-
- int sgp30_get_serial_id(uint8_t id[6]);//SGP30读取序列化方法
-
- int sgp30_soft_reset(void);//SGP30软复位方法
-
-
-
- private:
-
- #ifdef HARD_I2C
-
- I2C *_i2c;//硬件I2C对象指针
-
- #endif
-
- int sgp30_iic_write(uint8_t addr, const uint8_t* buf, uint32_t len);//SGP30 I2C写数据方法
-
- int sgp30_iic_read(uint8_t addr, uint8_t* buf, uint32_t len);//SGP30 I2C读数据方法
-
- uint8_t sgp30_checksum(const uint8_t* buf, uint32_t len);//SGP30和校验方法
-
- };
-
-
-
- #endif
-
-
-
cpp文件实现各个成员函数和构造函数:
- #include "SGP30.h"
-
-
-
- void GPIO_I2C::SGP30_SCK_L() { _scl_io->write(0); }
-
- void GPIO_I2C::SGP30_SCK_H() { _scl_io->write(1); }
-
- void GPIO_I2C::SGP30_SDA_L() { _sda_io->write(0); }
-
- void GPIO_I2C::SGP30_SDA_H() { _sda_io->write(1); }
-
-
-
- int GPIO_I2C::SGP30_READ_SDA() {
-
- if (_sda_io->read() == 1)
-
- return 1;
-
- else
-
- return 0;
-
- }
-
-
-
- //构造函数
-
- GPIO_I2C::GPIO_I2C(PinName scl, PinName sda) {
-
- #ifndef HARD_I2C
-
- printf("i2c use %d for scl,%d for sda\r\n", scl, sda);
-
- //scl对象指针实例化
-
- _scl_io = new DigitalOut(scl);
-
- //sda对象指针实例化
-
- _sda_io = new DigitalInOut(sda);
-
- //设置sda输出模式
-
- _sda_io->output();
-
-
-
- //拉高时钟引脚
-
- _scl_io->write(1);
-
- //拉高数据引脚
-
- _sda_io->write(1);
-
- #endif
-
- }
-
-
-
- //析构函数
-
- GPIO_I2C::~GPIO_I2C() {
-
- //释放资源
-
- #ifndef HARD_I2C
-
- delete _scl_io;
-
- delete _sda_io;
-
- #endif
-
- }
-
-
-
- //设置SDA输出模式方法
-
- void GPIO_I2C::SDA_SET_OUT() {
-
- //设置SDA输出模式
-
- _sda_io->output();
-
- //设置SDA输出低电平
-
- _sda_io->write(0);
-
- }
-
-
-
- //设置SDA输入模式方法
-
- void GPIO_I2C::SDA_SET_IN() {
-
- //设置SDA无上、下拉
-
- _sda_io->mode(PullNone);
-
- //设置SDA输入模式
-
- _sda_io->input();
-
- }
-
-
-
- void GPIO_I2C::sgp30_delay_us(uint32_t us) { wait_us(us); }
-
- void GPIO_I2C::sgp30_delay_ms(uint32_t nms) { wait_ms(nms); }
-
-
-
- void GPIO_I2C::IIC_Start(void) {
-
- SDA_SET_OUT();
-
- SGP30_SDA_H();
-
- SGP30_SCK_H();
-
- sgp30_delay_us(5);
-
- SGP30_SDA_L(); // START:when CLK is high,DATA change form high to low
-
- sgp30_delay_us(6);
-
- SGP30_SCK_L();
-
- }
-
-
-
- void GPIO_I2C::IIC_Stop(void) {
-
- SDA_SET_OUT();
-
- SGP30_SCK_L();
-
- SGP30_SDA_L(); // STOP:when CLK is high DATA change form low to high
-
- SGP30_SCK_H();
-
- sgp30_delay_us(6);
-
- SGP30_SDA_H();
-
- sgp30_delay_us(6);
-
- }
-
-
-
- uint8_t GPIO_I2C::IIC_Wait_Ack(void) {
-
- uint16_t tempTime = 0;
-
- SGP30_SDA_H();
-
- sgp30_delay_us(1);
-
- SDA_SET_IN();
-
- SGP30_SCK_H();
-
- sgp30_delay_us(1);
-
- while (SGP30_READ_SDA()) {
-
- tempTime++;
-
- wait_ms(10);
-
- if (tempTime > 250) {
-
- IIC_Stop();
-
- return 1;
-
- }
-
- }
-
- SGP30_SCK_L();
-
- return 0;
-
- }
-
-
-
- void GPIO_I2C::IIC_Ack(void) {
-
- SGP30_SCK_L();
-
- SDA_SET_OUT();
-
- SGP30_SDA_L();
-
- sgp30_delay_us(2);
-
- SGP30_SCK_H();
-
- sgp30_delay_us(5);
-
- SGP30_SCK_L();
-
- }
-
-
-
- void GPIO_I2C::IIC_NAck(void) {
-
- SGP30_SCK_L();
-
- SDA_SET_OUT();
-
- SGP30_SDA_H();
-
- sgp30_delay_us(2);
-
- SGP30_SCK_H();
-
- sgp30_delay_us(5);
-
- SGP30_SCK_L();
-
- }
-
-
-
- void GPIO_I2C::IIC_Send_Byte(uint8_t txd) {
-
- uint8_t t;
-
- SDA_SET_OUT();
-
- SGP30_SCK_L();
-
- for (t = 0; t < 8; t++) {
-
- if ((txd & 0x80) > 0) // 0x80 1000 0000
-
- SGP30_SDA_H();
-
- else
-
- SGP30_SDA_L();
-
- txd <<= 1;
-
- sgp30_delay_us(2);
-
- SGP30_SCK_H();
-
- sgp30_delay_us(2);
-
- SGP30_SCK_L();
-
- sgp30_delay_us(2);
-
- }
-
- }
-
-
-
- uint8_t GPIO_I2C::IIC_Read_Byte(uint8_t ack) {
-
- uint8_t i, receive = 0;
-
- SDA_SET_IN();
-
- for (i = 0; i < 8; i++) {
-
- SGP30_SCK_L();
-
- sgp30_delay_us(2);
-
- SGP30_SCK_H();
-
- receive <<= 1;
-
- if (SGP30_READ_SDA())
-
- receive++;
-
- sgp30_delay_us(1);
-
- }
-
- if (!ack)
-
- IIC_NAck();
-
- else
-
- IIC_Ack();
-
- return receive;
-
- }
-
-
-
- SGP30::SGP30(PinName scl, PinName sda) : GPIO_I2C(scl, sda) {
-
- #ifdef HARD_I2C
-
- _i2c = new I2C(I2C_SDA, I2C_SCL);
-
- _i2c->frequency(100000);
-
- #endif
-
- }
-
- SGP30::~SGP30() {}
-
- int SGP30::sgp30_iic_write(uint8_t addr, const uint8_t *buf, uint32_t len) {
-
- #ifdef HARD_I2C
-
- //_i2c->write(addr, buf, len,false);
-
- _i2c->write((int)addr, (char *)buf, (int)len, false);
-
- return 0;
-
- #else
-
- int i;
-
- IIC_Start();
-
- IIC_Send_Byte(addr);
-
- IIC_Wait_Ack();
-
- for (i = 0; i < len; i++) {
-
- IIC_Send_Byte(buf[i]);
-
- IIC_Wait_Ack();
-
- }
-
- IIC_Stop();
-
- return 0;
-
- #endif
-
- }
-
-
-
- int SGP30::sgp30_iic_read(uint8_t addr, uint8_t *buf, uint32_t len) {
-
- #ifdef HARD_I2C
-
- _i2c->read((int)addr, (char *)buf, (int)len, false);
-
- #else
-
- int i;
-
- IIC_Start();
-
- IIC_Send_Byte(addr);
-
- IIC_Wait_Ack();
-
- for (i = 0; i < len - 1; i++) {
-
- buf[i] = IIC_Read_Byte(1);
-
- }
-
- buf[i] = IIC_Read_Byte(0); // SGP30接收数据时候的最后一个字节不需要等待ACK
-
- IIC_Stop();
-
- #endif
-
- return 0;
-
- }
-
-
-
- int SGP30::sgp30_get_serial_id(uint8_t id[6]) {
-
- uint8_t buf[32];
-
- uint8_t crc[3];
-
-
-
- buf[0] = (SGP30_CMD_GET_SERIAL_ID & 0XFF00) >> 8;
- buf[1] = (SGP30_CMD_GET_SERIAL_ID & 0X00FF);
-
-
-
- if (sgp30_iic_write(SGP30_ADDR_WRITE, buf, 2) < 0)
-
- return -1;
-
-
-
- if (sgp30_iic_read(SGP30_ADDR_READ, buf, 9) < 0)
-
- return -2;
-
-
-
- crc[0] = buf[2];
-
- crc[1] = buf[5];
-
- crc[2] = buf[8];
-
-
-
- id[0] = buf[0];
-
- id[1] = buf[1];
-
- id[2] = buf[3];
-
- id[3] = buf[4];
-
- id[4] = buf[6];
-
- id[5] = buf[7];
-
-
-
- if (sgp30_checksum(&id[0], 2) != crc[0] ||
-
- sgp30_checksum(&id[2], 2) != crc[1] ||
-
- sgp30_checksum(&id[4], 2) != crc[2])
-
- return -3;
-
-
-
- return 0;
-
- }
-
-
-
- uint8_t SGP30::sgp30_checksum(const uint8_t *buf, uint32_t len) {
-
- const uint8_t Polynomial = 0x31;
-
- uint8_t Initialization = 0XFF;
-
- uint8_t i = 0, k = 0;
-
- while (i < len) {
-
- Initialization ^= buf[i++];
-
- for (k = 0; k < 8; k++) {
-
- if (Initialization & 0X80)
-
- Initialization = (Initialization << 1) ^ Polynomial;
-
- else
-
- Initialization = (Initialization << 1);
-
- }
-
- }
-
- return Initialization;
-
- }
-
-
-
- int SGP30::sgp30_soft_reset(void) {
-
- uint8_t cmd = 0X06;
-
- return sgp30_iic_write(0X00, &cmd, 1);
-
- }
-
-
-
- int SGP30::sgp30_init(void) {
-
- uint8_t buf[2];
-
-
-
- // 软件复位
-
- if (sgp30_soft_reset() < 0)
-
- return -2;
-
-
-
- // 等待复位完成
-
- sgp30_delay_ms(50);
-
-
-
- buf[0] = (SGP30_CMD_INIT_AIR_QUALITY & 0XFF00) >> 8;
- buf[1] = (SGP30_CMD_INIT_AIR_QUALITY & 0X00FF);
-
-
-
- // 初始化控制测量参数
-
- if (sgp30_iic_write(SGP30_ADDR_WRITE, buf, 2) < 0)
-
- return -3;
-
- printf("sgp30 init end\r\n");
-
- return 0;
-
- }
-
-
-
- int SGP30::sgp30_read(uint16_t *CO2, uint16_t *TVOC) {
-
- uint8_t buf[8] = {0};
-
-
-
- buf[0] = (SGP30_CMD_MEASURE_AIR_QUALITY & 0XFF00) >> 8;
- buf[1] = (SGP30_CMD_MEASURE_AIR_QUALITY & 0X00FF);
-
-
-
- // 启动空气质量测量
-
- if (sgp30_iic_write(SGP30_ADDR_WRITE, buf, 2) < 0)
-
- return -1;
-
-
-
- // 等待测量完成
-
- sgp30_delay_ms(1000);
-
-
-
- // 读取收到的数据
-
- if (sgp30_iic_read(SGP30_ADDR_READ, buf, 6) < 0)
-
- return -2;
-
-
-
- // 校验CRC
-
- if (sgp30_checksum(&buf[3], 2) != buf[5])
-
- return -3;
-
-
-
- if (CO2 != NULL)
-
- *CO2 = (buf[0] << 8) | buf[1];
-
- if (TVOC != NULL)
-
- *TVOC = (buf[3] << 8) | buf[4];
-
-
-
- return 0;
-
- }
-
工作线程sgp30_work_thread设计如下,首先new一个SGP30对象,然后调用初始化方法,读取序列号,读取传感器数据:
- void sgp30_work_thread() {
-
- int ret;
-
- SGP30 *sgp30 = new SGP30(I2C_SCL, I2C_SDA);
-
- DigitalOut led1(LED1);
-
- uint16_t TVOC = 0, CO2 = 0;
-
- uint8_t ID[6] = {0};
-
- while (sgp30->sgp30_init() < 0) {
-
- printf(" sgp30 init fail\r\n");
-
- wait_ms(1000);
-
- }
-
-
-
- if (sgp30->sgp30_get_serial_id(ID) < 0) {
-
- printf(" sgp30 read serial id failed\r\n");
-
- } else {
-
- printf("SGP30 Serial number: ");
-
- for (int i = 0; i < 6; i++)
-
- printf("%02X", ID[i]);
-
- printf("\r\n");
-
- }
-
- printf("sgp30 wait air for init");
-
- fflush(stdout);
-
- do {
-
- ret = sgp30->sgp30_read(&CO2, &TVOC);
-
- if (ret < 0) {
-
- printf("SGP30 read failed,ret=%d\r\n", ret);
-
- } else {
-
- printf("-");
-
- fflush(stdout);
-
- }
-
- } while (TVOC == 0 && CO2 == 400);
-
- printf("\r\n");
-
- while (true) {
-
- ret = sgp30->sgp30_read(&CO2, &TVOC);
-
- if (ret < 0) {
-
- printf(" sgp30 read fail,ret=%d\r\n", ret);
-
- } else {
-
- printf("CO2:%5dppm TVOC:%5dppb\r\n", CO2, TVOC);
-
- }
-
- led1 = !led1;
-
- ThisThread::sleep_for(1000);
-
- }
-
- }
编译结果:STM32WB55拥有1 MB flash,256 KB SRAM,运行C++写的RTOS+蓝牙协议栈毫无压力。
Mbed Studio界面类似vscode,智能提示、自动补全等功能十分完善,代码编辑体验吊打自家的KEIL MDK。
连接stm32wb55开发板运行运行结果:
总结:从编译出的二进制文件大小,RAM使用情况,运行速度可以看出,使用C++开发并不会造成资源消耗过大的情况(主要看交叉编译器的性能),且C++能够和C混合编程,能显著的提高C在处理面向对象类问题上开发效率不足的缺点,尤其是在处理复杂一点的通信协议上如加解密,往往能达到事半功倍的效果。
然而主大多数MCU的flash容量在32KB~2MB左右,SRAM通常低于1MB(不考虑外部扩展),这样就限制C++中的STL模板,运行时多态等会造成内存“爆炸”的高级特性无法使用,如果我们只使用支持class的C++,这样就不必利用C结构体+函数指针的写法来实现面向对象的特性。:
---------------------
作者:dql2015
链接:https://bbs.21ic.com/icview-3278652-1-1.html
来源:21ic.com
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