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我从连接到 esp8266（Nodemcu v0.9）的 Nextion 返回的数据有问题。我正在以 9600 b/s 的速度与 Nextion 通信。

我有代码可以解析通过 IDE 的串行控制台输入的命令，并将适当的命令发送到 Nextion。这里的相关命令是“getn xxxx”，它要求从 Nextion 获取数值。

例如，“getn 123”发送一个“get 123”，期望得到一个数字结果。（有一个 'gets 123' 发送一个 'get "123"' 但这里没有使用）

当我发送一个“getn 123”后跟一个“getn 222”时，这就是我得到的

**ESP8266**

//1st getn command. Note only 7 bytes come back and missing 3rd 0xFF in returned data
Processing command: getn 123
Sending [get 123]
found 7 bytes
71 7b 00 00 00 ff ff

//2nd getn command. Note additional leading 0xFF and missing 3rd 0xFF in returned data
Processing command: getn 222
Sending [get 222]
found 8 bytes
ff 71 de 00 00 00 ff ff

If I connect an Arduino Nano instead of the esp8266, the same code works perfectly!

**nano** (I only execute one 'getn 123' since it works ok

Processing command: getn 123
Sending [get 123]
found 8 bytes
71 7b 00 00 00 ff ff ff

请参阅下面的代码清单。

#include <SoftwareSerial.h>

#define SERIAL_TIMEOUT 3000

#ifdef ESP8266
  // ESP8266
  #define MY_RX 5  // NEXTION TX, esp8266 D1
  #define MY_TX 4  // NEXTION RX, esp8266 D2
#else
  // arduino, nano and similar
  #define MY_RX 11  // NEXTION TX,
  #define MY_TX 10  // NEXTION RX,
#endif

SoftwareSerial mySerial(MY_RX, MY_TX);

char serOutBuf[128];
char cmdBuf[64] = { 0 };

void setup() {
  Serial.begin(115200);
  while(Serial.available()) {
    Serial.read();
  }

  // Nextion comms are at 9600 b/s
  mySerial.begin(9600);
  Serial.println("Ready");
}

void loop() {
  int charsRead = 0;

  cmdBuf[0] = 0;

  if (Serial.available()) {
    charsRead = Serial.readBytesUntil('\n', cmdBuf, sizeof(cmdBuf) - 1);
    cmdBuf[charsRead] = 0;

    processCmd(cmdBuf);
  }
}

void processCmd(char *cmdBuf) {
  char *p = cmdBuf;
  char tmpBuf[128] = { 0 };

  do {    // dummy loop that allows multiple exits to a single point
    Serial.print("Processing command: ");Serial.println(cmdBuf);

    if (strncmp(cmdBuf, "send ", 5) == 0) {
      p = cmdBuf + 5; // skip 'send '
      while (*p == ' ') { // skip leading spaces
        p++;
      }

      sendCommand(p);
      break;
    }

    // get numeric value from Nextion. There is a 'gets' too but not shown here
    if (strncmp(cmdBuf, "getn ", 5) == 0) {
      p = cmdBuf + 5;
      while (*p == ' ') {
        p++;
      }

      int n = 0;
      sprintf(tmpBuf, "get %s", p);        // build command to send
      bool ret = getNumber(&n, tmpBuf);    // get number value from Nextion
      
      // the next 2 lines cater for the fact the Nano does not support Serial.printf()
      sprintf(serOutBuf, "result %d =  %d\n", ret, n);
      Serial.print(serOutBuf);

      break;
    }
  } while (false);  // dummy loop
}

boolean sendCommand(char *cmd) {
  sprintf(serOutBuf, "Sending [%s]\n", cmd);
  Serial.print(serOutBuf);

  mySerial.print(cmd);
  mySerial.write(0xFF);
  mySerial.write(0xFF);
  mySerial.write(0xFF);
  delay(20);

  return true;
}

bool getNumber(int *n, char *cmd) {
  bool res = false;

  Serial.print(serOutBuf);

  if (n) {
    sendCommand(cmd);

    byte buf[8];
    int l = mySerial.readBytes(buf, sizeof(buf));
    sprintf(serOutBuf, "found %d bytes\n", l);
    Serial.print(serOutBuf);

    for (int i = 0; i < l; i++) {
      sprintf(serOutBuf, "%02x ", (byte)buf[i]);
      Serial.print(serOutBuf);
    }
    Serial.println("");

    if (buf[0] == 0x71 && buf[5] == 0xff && buf[6] == 0xff && buf[7] == 0xff) {
      *n = ((uint32_t)buf[4] << 24) | ((uint32_t)buf[3] << 16) | ((uint32_t)buf[2] << 8) | buf[1];
      res = true;
    }
  }

  return res;
}

任何有关上述内容的帮助将不胜感激！

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