"conversion from void to non scalar type string"是什么意思？

what is meaning of "conversion from void to non scalar type string"?

本文关键字：string 是什么 意思 type non conversion from void to scalar      更新时间：2023-10-16

我想使用 sim900a 模块和 arduino uno 通过短信将 GPS 坐标发送到特定号码，当他们从短信(如"发送 GPS"(请求时，这里编写了代码，但是当我编译代码时，我收到"错误：请求从'void'转换为非标量类型'字符串'".....请任何帮助不胜感激...提前谢谢你

void loop() {
    RecieveMessage();
    if (sim.available() > 0)
    {
        Serial.write(sim.read());
    }
    if(sim.read()=="SEND GPS")
    {
        SendMessage();
    }
}
void RecieveMessage()
{
    Serial.println ("SIM800L Read an SMS");
    sim.println("AT+CNMI=2,2,0,0,0");
    Serial.write ("Unread Message done");
}
void SendMessage()
{
    //Serial.println ("Sending Message");
    sim.println("AT+CMGF=1");
    sim.println("AT+CMGS="" + number + ""r");
    while (sgps.available())
    {
        int c = sgps.read();
        if (gps.encode(c))
        {
            float slat,slon;
            String loc=gps.f_get_position(&slat, &slon);
        }
        String SMS = String("http://maps.google.com/maps?q=loc:")+String(loc);
        sim.println(SMS);
        sim.println((char)26);
    }

gps.f_get_position返回 void，但您正在将其分配给String。只需删除String loc= 

void loop()
{
  while (sgps.available())
  {
    int c = sgps.read();
    if (gps.encode(c))
    {
      float slat,slon;
      gps.f_get_position(&slat, &slon);
      Serial.print("Latitude :");
      Serial.println(slat, 6);
      Serial.print("Longitude:");
      Serial.println(slon, 6);
    
      String loc = String(slat,6)+" "+String(slon,6);
      Serial.println ("Sending Message");
      sim.println("AT+CMGF=1");    //Sets the GSM Module in Text Mode
      delay(1000);
      Serial.println ("Set SMS Number");
      sim.println("AT+CMGS="" + number + ""r"); //Mobile phone number to send message
      delay(1000);
      String SMS = String("https://www.google.com/maps/") + String(slat,6)+","+String(slon,6);
      sim.println(SMS);
      delay(100);
      sim.println((char)26);// ASCII code of CTRL+Z
      delay(1000);
      _buffer = _readSerial();
    }
  }
}
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