if!((message->payload[1] == 0x03) && (message->payload[2] == 0x02)) C语言这样写对吗

这段 C 语言代码有语法错误。应该写成：

if (!((message->payload[1] == 0x03) && (message->payload[2] == 0x02)))

该代码使用了逻辑非运算符 `!` ，表示如果括号内的条件不成立，则执行条件语句。条件语句中使用了逻辑与运算符 `&&` ，表示两个条件都必须成立才返回真。其中，`message` 是一个指向结构体的指针，`payload` 是结构体中的一个数组，`[1]` 和 `[2]` 分别表示数组中的第二个和第三个元素。

因此，该代码的意思是：如果 `message` 结构体中的 `payload` 数组的第二个元素是 `0x03`，且第三个元素是 `0x02`，则不执行条件语句，否则执行条件语句。

相关问题

S32K144-EVB开发板CAN实例代码

以下是S32K144-EVB开发板CAN实例代码：

#include "S32K144.h"
#include "can.h"
#include "clocks_and_modes.h"
#include "gpio.h"
#include "interrupt_manager.h"

#define CAN0_TX_PIN 27U
#define CAN0_RX_PIN 26U

#define CAN0_TX_MUX 2U
#define CAN0_RX_MUX 2U

#define CAN0_RX_MSG_BUF_NUM (4U)

#define CAN0_BASE_ADDR (0x40024000U)
#define CAN0_RX_FIFO_ID (0x100U)
#define CAN0_RX_FIFO_NUM (8U)

static uint8_t can0RxMsgBuf[CAN0_RX_MSG_BUF_NUM][CAN_MESSAGE_BUFFER_MAX_PAYLOAD_SIZE];

void Can0_RxIsr(void);

void InitCan0(void)
{
    /* Enable clock for PORTA */
    PCC->PCCn[PCC_PORTA_INDEX] |= PCC_PCCn_CGC_MASK;
    /* Configure CAN0_TX_PIN and CAN0_RX_PIN as alternative function (Alt2) */
    PORTA->PCR[CAN0_TX_PIN] = PORT_PCR_MUX(CAN0_TX_MUX);
    PORTA->PCR[CAN0_RX_PIN] = PORT_PCR_MUX(CAN0_RX_MUX);
    /* Set the bit rate to 500 kbps with a 8 MHz clock */
    const uint32_t can0ClkFreq = 8000000U;
    const uint32_t baudRate = 500000U;
    const uint32_t prescaler = (can0ClkFreq / (baudRate * 20U)) - 1U;
    CAN0->CTRL1 &= ~CAN_CTRL1_CLKSRC_MASK;
    CAN0->CTRL1 |= CAN_CTRL1_CLKSRC(1U);
    CAN0->CTRL1 |= CAN_CTRL1_PRESDIV(prescaler);
    /* Enable CAN0 */
    PCC->PCCn[PCC_FlexCAN0_INDEX] |= PCC_PCCn_CGC_MASK;
    /* Enable individual RX FIFO filters */
    CAN0->MCR |= CAN_MCR_IRMQ_MASK;
    /* Enable RX FIFO */
    CAN0->MCR |= CAN_MCR_RFEN_MASK;
    /* Configure RX FIFO ID filter */
    CAN0->RXFIFO.IDTABLE[0] = 0x80000000U;
    CAN0->RXFIFO.IDTABLE[1] = 0x80000000U;
    /* Configure RX FIFO filter element */
    CAN0->RXIMR[CAN0_RX_FIFO_NUM] = 0xFFFFFFFFU;
    CAN0->RXMGMASK = 0x80000000U;
    CAN0->RXFGMASK = 0x80000000U;
    /* Enable RX FIFO interrupt */
    CAN0->IMASK1 |= CAN_IMASK1_BUF5M_MASK;
    /* Configure RX message buffers */
    for (uint32_t msgBufIdx = 0U; msgBufIdx < CAN0_RX_MSG_BUF_NUM; msgBufIdx++)
    {
        /* Configure RX message buffer filter */
        CAN0->RAMn[msgBufIdx].ID = (CAN_RAMn_ID_STD(0x7FFU) | CAN_RAMn_IDE_MASK);
        /* Configure RX message buffer payload size */
        CAN0->RAMn[msgBufIdx].CS = CAN_CS_DLC(CAN_MESSAGE_BUFFER_MAX_PAYLOAD_SIZE);
        /* Configure RX message buffer for reception */
        CAN0->RAMn[msgBufIdx].CS |= CAN_CS_CODE(CAN_CS_CODE_RX_INACTIVE);
    }
    /* Configure NVIC for RX FIFO interrupt */
    const IRQn_Type can0RxIrqId = IRQ_CAN0_ORed_Message_buffer;
    INT_SYS_EnableIRQ(can0RxIrqId);
    INT_SYS_SetPriority(can0RxIrqId, 3U);
}

void Can0_RxIsr(void)
{
    uint32_t msgBufIdx = 0U;
    /* Read RX FIFO and dispatch messages */
    while (CAN0->IFLAG1 & CAN_IFLAG1_BUF5I_MASK)
    {
        /* Clear RX FIFO interrupt flag */
        CAN0->IFLAG1 |= CAN_IFLAG1_BUF5I_MASK;
        /* Read RX FIFO element */
        const uint32_t fifoElemIdx = 0U;
        const uint32_t fifoElemAddr = (CAN0_BASE_ADDR + 0x00000C00U + (fifoElemIdx * 0x10U));
        uint32_t fifoElemData[4] = {0U};
        for (uint32_t i = 0U; i < 4U; i++)
        {
            fifoElemData[i] = (*(volatile uint32_t *)(fifoElemAddr + (i * 4U)));
        }
        /* Process RX FIFO element */
        if ((fifoElemData[0] & CAN_RAMn_IDE_MASK) == CAN_RAMn_IDE_MASK)
        {
            /* Extended ID */
            const uint32_t rxMsgId = (fifoElemData[0] & CAN_RAMn_ID_MASK_EXT);
            const uint8_t rxMsgDlc = (fifoElemData[1] & CAN_RAMn_CS_DLC_MASK);
            uint8_t rxMsgPayload[CAN_MESSAGE_BUFFER_MAX_PAYLOAD_SIZE] = {0U};
            for (uint32_t i = 0U; i < (rxMsgDlc >> 2U); i++)
            {
                ((uint32_t *)rxMsgPayload)[i] = fifoElemData[i + 2U];
            }
            /* Find free RX message buffer and configure it for reception */
            for (msgBufIdx = 0U; msgBufIdx < CAN0_RX_MSG_BUF_NUM; msgBufIdx++)
            {
                if ((CAN0->RAMn[msgBufIdx].CS & CAN_CS_CODE_MASK) == CAN_CS_CODE_RX_INACTIVE)
                {
                    break;
                }
            }
            if (msgBufIdx < CAN0_RX_MSG_BUF_NUM)
            {
                /* Configure RX message buffer filter */
                CAN0->RAMn[msgBufIdx].ID = (CAN_RAMn_ID_EXT(rxMsgId) | CAN_RAMn_IDE_MASK);
                /* Configure RX message buffer payload size */
                CAN0->RAMn[msgBufIdx].CS = CAN_CS_DLC(rxMsgDlc);
                /* Configure RX message buffer for reception */
                CAN0->RAMn[msgBufIdx].CS |= CAN_CS_CODE(CAN_CS_CODE_RX_FULL);
                /* Copy RX message payload */
                for (uint32_t i = 0U; i < CAN_MESSAGE_BUFFER_MAX_PAYLOAD_SIZE; i++)
                {
                    can0RxMsgBuf[msgBufIdx][i] = rxMsgPayload[i];
                }
            }
            else
            {
                /* RX message buffer not available */
            }
        }
        else
        {
            /* Standard ID */
        }
    }
}

void SendCan0Msg(const uint32_t msgId, const uint8_t * const msgPayload, const uint32_t msgPayloadSize)
{
    /* Find free TX message buffer and configure it for transmission */
    uint32_t txMsgBufIdx = 0U;
    for (txMsgBufIdx = 0U; txMsgBufIdx < CAN0_TX_MSG_BUF_NUM; txMsgBufIdx++)
    {
        if ((CAN0->RAMn[txMsgBufIdx].CS & CAN_CS_CODE_MASK) == CAN_CS_CODE_TX_INACTIVE)
        {
            break;
        }
    }
    if (txMsgBufIdx < CAN0_TX_MSG_BUF_NUM)
    {
        /* Configure TX message buffer ID */
        CAN0->RAMn[txMsgBufIdx].ID = (CAN_RAMn_ID_STD(msgId) | CAN_RAMn_IDE_MASK);
        /* Configure TX message buffer payload size */
        CAN0->RAMn[txMsgBufIdx].CS = CAN_CS_DLC(msgPayloadSize);
        /* Copy TX message payload */
        for (uint32_t i = 0U; i < msgPayloadSize; i++)
        {
            can0TxMsgBuf[txMsgBufIdx][i] = msgPayload[i];
        }
        /* Configure TX message buffer for transmission */
        CAN0->RAMn[txMsgBufIdx].CS |= CAN_CS_CODE(CAN_CS_CODE_TX_INACTIVE);
    }
    else
    {
        /* TX message buffer not available */
    }
}

int main(void)
{
    /* Init board hardware */
    InitClocksAndModes();
    InitGpio();
    InitCan0();
    /* Send CAN message */
    const uint32_t msgId = 0x123U;
    const uint8_t msgPayload[] = {0x11U, 0x22U, 0x33U};
    const uint32_t msgPayloadSize = sizeof(msgPayload);
    SendCan0Msg(msgId, msgPayload, msgPayloadSize);
    /* Main loop */
    while (1U)
    {
        /* Do nothing */
    }
}

这个例程中，我们使用了S32K144-EVB开发板上的CAN0模块，并且配置了一个接收FIFO和四个接收消息缓冲区。在初始化过程中，我们设置了CAN0的波特率为500 kbps，并且启用了CAN0模块和RX FIFO中断。在主函数中，我们发送了一个CAN消息，并且在接收中断处理函数Can0_RxIsr中读取并处理了接收到的CAN消息。

package main import ( "fmt" "log" "os" "time" "github.com/goburrow/modbus" "github.com/tarm/serial" MQTT "github.com/eclipse/paho.mqtt.golang" ) // 定义回调函数，处理订阅的消息 var f MQTT.MessageHandler = func(client MQTT.Client, msg MQTT.Message) { fmt.Printf("TOPIC: %s\n", msg.Topic()) fmt.Printf("MSG: %s\n", msg.Payload()) } func main() { // 创建新的客户端 opts := MQTT.NewClientOptions().AddBroker("tcp://localhost:1883") opts.SetClientID("golang-client") opts.SetDefaultPublishHandler(f) c := MQTT.NewClient(opts) if token := c.Connect(); token.Wait() && token.Error() != nil { panic(token.Error()) } // 订阅主题 if token := c.Subscribe("golang/topic", 0, nil); token.Wait() && token.Error() != nil { fmt.Println(token.Error()) os.Exit(1) } // 连接串口 c := &serial.Config{Name: "/dev/ttyS0", Baud: 115200} s, err := serial.OpenPort(c) if err != nil { log.Fatal(err) } // 创建 Modbus 从机实例 handler := modbus.NewRTUClientHandler(s) handler.BaudRate = 115200 handler.DataBits = 8 handler.Parity = "N" handler.StopBits = 1 handler.SlaveId = 1 handler.Timeout = 5 * time.Second defer handler.Close() client := modbus.NewClient(handler) // 读取寄存器 results, err := client.ReadHoldingRegisters(1, 2) if err != nil { log.Fatal(err) } fmt.Println(results) // 输出读取到的寄存器值 // 设置寄存器 err = client.WriteMultipleRegisters(1, 2, []byte{0x01, 0x02}) if err != nil { log.Fatal(err) } // 发布消息 for i := 0; i < 5; i++ { text := fmt.Sprintf("this is msg #%d!", i) token := c.Publish("golang/topic", 0, false, text) token.Wait() } time.Sleep(3 * time.Second) // 断开连接 if token := c.Unsubscribe("golang/topic"); token.Wait() && token.Error() != nil { fmt.Println(token.Error()) os.Exit(1) } c.Disconnect(250) }

这是一段 Go 语言程序，在这段程序中，包含了多个包的导入，包括 fmt、log、os、time、modbus 和 serial。它还引入了 paho.mqtt.golang 包，用于处理 MQTT 协议相关的功能。

在 main 函数中，定义了一个名为 f 的 MQTT.MessageHandler 类型的变量，这个变量是一个匿名函数，用于处理订阅的消息。

接下来，程序创建了一个新的 MQTT 客户端，并设置了客户端的 ID 和默认的发布处理函数。然后，程序尝试连接到本地的 MQTT 服务器，并在连接成功之后执行相关操作。