C中数据类型的问题

Question

我正在尝试 Arduino 终极 GPS 突破，我想从 GPS 中获取经度和纬度。然后我想通过射频无线发送这两个变量。如下图所示：

我为名为 panstamp 的 RF 模块使用了一个库，以便能够从 Arduino 1 发送经度和纬度，并在 Arduino 2 中接收它们。如下面的代码所示：

传输：

    void send_data() {
    CCPACKET data;
    data.length=2;

    float lon=26.533255;
    float lat=27.533463;


    data.data[0]=lon;
    data.data[1]=lat;
    if(cc1101.sendData(data)){
    Serial.println(data.data[0]);
    Serial.println(data.data[1]);

    Serial.println(" sent ok ");
    return true;
    }else{
    Serial.println("sent failed ");
    return false;
    }

 }

接收：

void loop(){
        float j = 0;
        lon = packet.data[j];
          Serial.print(lon);
          Serial.print(" ");
        float k = 1;
        lat = packet.data[k];
          Serial.print(lat);
          Serial.println(".");
}

在发送和接收时完美运行:)

问题是当我收到这两个变量时，我只收到 lon 26.00 和 lat 27.00 而不是 lon 26.533255 lat 27.533463 如我所料。

我假设的数据类型存在一些错误。我调查了 panstamp 库以找到改变类型但没有成功的东西。

这是 CCPACKET 的头文件：

#ifndef _CCPACKET_H
#define _CCPACKET_H

#include "Arduino.h"

/**
 * Buffer and data lengths
 */
#define CC1101_BUFFER_LEN        64
#define CC1101_DATA_LEN          CC1101_BUFFER_LEN - 3

/**
 * Class: CCPACKET
 * 
 * Description:
 * CC1101 data packet class
 */
class CCPACKET
{
  public:
    /**
     * Data length
     */
    byte length;

    /**
     * Data buffer
     */
    byte data[CC1101_DATA_LEN];

    /**
     * CRC OK flag
     */
    boolean crc_ok;

    /**
     * Received Strength Signal Indication
     */
    byte rssi;

    /**
     * Link Quality Index
     */
    byte lqi;
};

#endif

以及发送数据/接收数据的源代码：

boolean CC1101::sendData(CCPACKET packet)
{
  byte marcState;
  bool res = false;

  // Declare to be in Tx state. This will avoid receiving packets whilst
  // transmitting
  rfState = RFSTATE_TX;

  // Enter RX state
  setRxState();

  // Check that the RX state has been entered
  while (((marcState = readStatusReg(CC1101_MARCSTATE)) & 0x1F) != 0x0D)
  {
    if (marcState == 0x11)        // RX_OVERFLOW
      flushRxFifo();              // flush receive queue
  }

  delayMicroseconds(500);

  // Set data length at the first position of the TX FIFO
  writeReg(CC1101_TXFIFO,  packet.length);
  // Write data into the TX FIFO
  writeBurstReg(CC1101_TXFIFO, packet.data, packet.length);

  // CCA enabled: will enter TX state only if the channel is clear
  setTxState();

  // Check that TX state is being entered (state = RXTX_SETTLING)
  marcState = readStatusReg(CC1101_MARCSTATE) & 0x1F;
  if((marcState != 0x13) && (marcState != 0x14) && (marcState != 0x15))
  {
    setIdleState();       // Enter IDLE state
    flushTxFifo();        // Flush Tx FIFO
    setRxState();         // Back to RX state

    // Declare to be in Rx state
    rfState = RFSTATE_RX;
    return false;
  }

  // Wait for the sync word to be transmitted
  wait_GDO0_high();

  // Wait until the end of the packet transmission
  wait_GDO0_low();

  // Check that the TX FIFO is empty
  if((readStatusReg(CC1101_TXBYTES) & 0x7F) == 0)
    res = true;

  setIdleState();       // Enter IDLE state
  flushTxFifo();        // Flush Tx FIFO

  // Enter back into RX state
  setRxState();

  // Declare to be in Rx state
  rfState = RFSTATE_RX;

  return res;
}


byte CC1101::receiveData(CCPACKET * packet)
{
  byte val;
  byte rxBytes = readStatusReg(CC1101_RXBYTES);

  // Any byte waiting to be read and no overflow?
  if (rxBytes & 0x7F && !(rxBytes & 0x80))
  {
    // Read data length
    packet->length = readConfigReg(CC1101_RXFIFO);
    // If packet is too long
    if (packet->length > CC1101_DATA_LEN)
      packet->length = 0;   // Discard packet
    else
    {
      // Read data packet
      readBurstReg(packet->data, CC1101_RXFIFO, packet->length);
      // Read RSSI
      packet->rssi = readConfigReg(CC1101_RXFIFO);
      // Read LQI and CRC_OK
      val = readConfigReg(CC1101_RXFIFO);
      packet->lqi = val & 0x7F;
      packet->crc_ok = bitRead(val, 7);
    }
  }
  else
    packet->length = 0;

  setIdleState();       // Enter IDLE state
  flushRxFifo();        // Flush Rx FIFO
  //cmdStrobe(CC1101_SCAL);

  // Back to RX state
  setRxState();

  return packet->length;
}

请有人帮助我:)

Panstamp 库的链接：PanStamp Library

Answer 1

在我看来，你在这里失去了你的洞察力：

float lon=26.533255;
float lat=27.533463;
data.data[0]=lon;
data.data[1]=lat;

因为根据这个数据是一个字节数组：

/**
 * Data buffer
 */
byte data[CC1101_DATA_LEN];

您需要正确缓冲数据。

Answer 2

浮点数=26.533255; 字节 *p = (字节 *)&lon;

for (int i = 0; i

如果它可以工作就这样做

Answer 3

HighPredator 是对的！

从 panstamp 库我们看到 CCPACKET::data 字段是一个 uint8_t 数组： https://github.com/panStamp/panstamp/wiki/CCPACKET#data

基本上在你写的时候：

float lon=26.533255;
float lat=27.533463;
data.data[0]=lon;
data.data[1]=lat;

编译器本质上是在做：

data.data[0]=uint8_t(lon); // So 26.533255f just becomes 26
data.data[1]=uint8_t(lat); // So 27.533463just becomes 27

您需要了解浮点类型，它是 4 字节长，因此您需要将数据包设为 8 字节长并像这样传输原始字节：

data.length = 8;
data.data[0] = ((uint8_t*)(&lon))[0]; // Transfer first byte of the float
data.data[1] = ((uint8_t*)(&lon))[1];
data.data[2] = ((uint8_t*)(&lon))[2];
data.data[3] = ((uint8_t*)(&lon))[3]; // Transfer last byte of the float

data.data[4] = ((uint8_t*)(&lat))[0]; // Transfer first byte of the float
data.data[5] = ((uint8_t*)(&lat))[1];
data.data[6] = ((uint8_t*)(&lat))[2];
data.data[7] = ((uint8_t*)(&lat))[3]; // Transfer last byte of the float

在接收端，您可以像这样重构浮点数：

float lon, lat;
((uint8_t*)(&lon))[0] = data.data[0]; // Place first byte
((uint8_t*)(&lon))[1] = data.data[1];
((uint8_t*)(&lon))[2] = data.data[2];
((uint8_t*)(&lon))[3] = data.data[3]; // Place last byte

((uint8_t*)(&lat))[0] = data.data[4]; // Place first byte
((uint8_t*)(&lat))[1] = data.data[5];
((uint8_t*)(&lat))[2] = data.data[6];
((uint8_t*)(&lat))[3] = data.data[7]; // Place last byte

希望对您有所帮助。