写一个freemodbus从站读寄存器数据的详细代码

好的，这里提供一个基于STM32的FreeModbus从站读寄存器数据的代码示例供参考：

/* FreeModbus includes */
#include "mb.h"
#include "mbutils.h"

/* STM32 includes */
#include "stm32f10x.h"

/* Define the number of registers */
#define REG_INPUT_NREGS     4
#define REG_HOLDING_NREGS   8

/* Define the start addresses of the input and holding registers */
#define REG_INPUT_START     1000
#define REG_HOLDING_START   2000

/* Define the buffer sizes */
#define BUF_SIZE            64

/* Define the USART baud rate */
#define USART_BAUDRATE      9600

/* Define the USART port */
#define USART_PORT          USART1

/* Define the GPIO pins for the USART */
#define USART_GPIO          GPIOA
#define USART_TX_PIN        GPIO_Pin_9
#define USART_RX_PIN        GPIO_Pin_10

/* Define the GPIO pins for the LED */
#define LED_GPIO            GPIOC
#define LED_PIN             GPIO_Pin_13

/* Define the slave address */
#define SLAVE_ADDRESS       0x01

/* Define the modbus mode (ASCII or RTU) */
#define MODBUS_MODE         MB_RTU

/* Define the modbus UART parameters */
#define MODBUS_UART         USART1
#define MODBUS_UART_BAUD    9600
#define MODBUS_UART_PARITY  USART_Parity_No
#define MODBUS_UART_STOP    USART_StopBits_1
#define MODBUS_UART_DATA    USART_WordLength_8b

/* Define the modbus timer parameters */
#define MODBUS_TIM          TIM2
#define MODBUS_TIM_FREQ     1000000
#define MODBUS_TIM_PRESC    71
#define MODBUS_TIM_PERIOD   100

/* Define the modbus timer interrupt priority */
#define MODBUS_TIM_IRQ_PRI  5

/* Define the modbus timer interrupt flag */
#define MODBUS_TIM_IRQ_FLAG TIM_IT_Update

/* Define the modbus timer interrupt function */
#define MODBUS_TIM_IRQ_FUNC TIM2_IRQHandler

/* Define the modbus timer interrupt handler */
#define MODBUS_TIM_IRQ_HANDLER MODBUS_TIM_IRQ_FUNC

/* Define the modbus timer interrupt vector */
#define MODBUS_TIM_IRQ_VECTOR TIM2_IRQn

/* Define the modbus timer interrupt vector table entry */
#define MODBUS_TIM_IRQ_ENTRY MODBUS_TIM_IRQ_HANDLER

/* Define the modbus timer interrupt enable */
#define MODBUS_TIM_IRQ_EN   TIM_IT_Update

/* Define the modbus timer interrupt disable */
#define MODBUS_TIM_IRQ_DIS  0

/* Define the modbus timer initialization function */
void modbus_timer_init( void );

/* Define the modbus timer interrupt function */
void modbus_timer_irq( void );

/* Define the modbus initialization function */
void modbus_init( void );

/* Define the modbus polling function */
void modbus_poll( void );

/* Define the input register buffer */
USHORT usRegInputStart = REG_INPUT_START;
USHORT usRegInputBuf[REG_INPUT_NREGS];

/* Define the holding register buffer */
USHORT usRegHoldingStart = REG_HOLDING_START;
USHORT usRegHoldingBuf[REG_HOLDING_NREGS];

/* Define the USART buffer */
uint8_t ucUSARTBuf[BUF_SIZE];

/* Define the USART buffer length */
uint16_t usUSARTLen = 0;

/* Define the LED state */
uint8_t ucLEDState = 0;

/* Define the main function */
int main( void )
{
    /* Initialize the system clock */
    SystemInit();

    /* Initialize the GPIO pins for the USART */
    RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOA, ENABLE );
    GPIO_InitTypeDef GPIO_InitStruct;
    GPIO_InitStruct.GPIO_Pin = USART_TX_PIN | USART_RX_PIN;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init( USART_GPIO, &GPIO_InitStruct );

    /* Initialize the GPIO pins for the LED */
    RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOC, ENABLE );
    GPIO_InitStruct.GPIO_Pin = LED_PIN;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init( LED_GPIO, &GPIO_InitStruct );

    /* Initialize the USART port */
    RCC_APB2PeriphClockCmd( RCC_APB2Periph_USART1, ENABLE );
    USART_InitTypeDef USART_InitStruct;
    USART_InitStruct.USART_BaudRate = USART_BAUDRATE;
    USART_InitStruct.USART_WordLength = USART_WordLength_8b;
    USART_InitStruct.USART_StopBits = USART_StopBits_1;
    USART_InitStruct.USART_Parity = USART_Parity_No;
    USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStruct.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
    USART_Init( USART_PORT, &USART_InitStruct );
    USART_Cmd( USART_PORT, ENABLE );

    /* Initialize the modbus timer */
    modbus_timer_init();

    /* Initialize the modbus */
    modbus_init();

    /* Main loop */
    while( 1 )
    {
        /* Poll the modbus */
        modbus_poll();

        /* Toggle the LED */
        if( ucLEDState )
        {
            GPIO_WriteBit( LED_GPIO, LED_PIN, Bit_RESET );
            ucLEDState = 0;
        }
        else
        {
            GPIO_WriteBit( LED_GPIO, LED_PIN, Bit_SET );
            ucLEDState = 1;
        }

        /* Delay */
        Delay( 100 );
    }
}

/* Define the modbus timer initialization function */
void modbus_timer_init( void )
{
    /* Enable the timer clock */
    RCC_APB1PeriphClockCmd( RCC_APB1Periph_TIM2, ENABLE );

    /* Configure the timer */
    TIM_TimeBaseInitTypeDef TIM_InitStruct;
    TIM_InitStruct.TIM_Prescaler = MODBUS_TIM_PRESC;
    TIM_InitStruct.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_InitStruct.TIM_Period = MODBUS_TIM_PERIOD;
    TIM_InitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_InitStruct.TIM_RepetitionCounter = 0;
    TIM_TimeBaseInit( MODBUS_TIM, &TIM_InitStruct );

    /* Enable the timer interrupt */
    NVIC_InitTypeDef NVIC_InitStruct;
    NVIC_InitStruct.NVIC_IRQChannel = MODBUS_TIM_IRQ_VECTOR;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = MODBUS_TIM_IRQ_PRI;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init( &NVIC_InitStruct );

    /* Enable the timer interrupt flag */
    TIM_ITConfig( MODBUS_TIM, MODBUS_TIM_IRQ_FLAG, ENABLE );

    /* Start the timer */
    TIM_Cmd( MODBUS_TIM, ENABLE );
}

/* Define the modbus timer interrupt function */
void modbus_timer_irq( void )
{
    /* Update the modbus timer */
    (void)pxMBPortCBTimerExpired();
}

/* Define the modbus initialization function */
void modbus_init( void )
{
    /* Initialize the modbus */
    eMBErrorCode eMBErrorCode = eMBInit( MODBUS_MODE, SLAVE_ADDRESS, MODBUS_UART, MODBUS_UART_BAUD, MODBUS_UART_PARITY, MODBUS_UART_DATA );
    if( eMBErrorCode != MB_ENOERR )
    {
        /* Handle the error */
    }

    /* Enable the modbus */
    eMBErrorCode = eMBEnable();
    if( eMBErrorCode != MB_ENOERR )
    {
        /* Handle the error */
    }
}

/* Define the modbus polling function */
void modbus_poll( void )
{
    /* Get the number of bytes in the USART buffer */
    uint16_t usBytes = USART_GetBytesAvailable( USART_PORT );

    /* If there are bytes in the buffer */
    if( usBytes > 0 )
    {
        /* Read the bytes from the USART buffer */
        USART_Read( USART_PORT, ucUSARTBuf, usBytes );

        /* Pass the bytes to the modbus */
        eMBErrorCode eMBErrorCode = eMBPoll( ucUSARTBuf, usBytes );
        if( eMBErrorCode != MB_ENOERR )
        {
            /* Handle the error */
        }
    }
}

/* Define the modbus timer interrupt handler */
void MODBUS_TIM_IRQ_HANDLER( void )
{
    /* Clear the timer interrupt flag */
    TIM_ClearITPendingBit( MODBUS_TIM, MODBUS_TIM_IRQ_FLAG );

    /* Call the modbus timer interrupt function */
    modbus_timer_irq();
}

以上是基于STM32的FreeModbus从站读寄存器数据的代码示例，仅供参考。具体实现需要根据具体的硬件平台和应用场景进行调整。