Question

我正在将rfid卡读入content.substring（1）。并且我已经将其设置为变量uidrf，但是我不能在我的firebase.set函数中将该变量用作值

当前我已经尝试了以下代码，但无法使其正常工作

//Show UID on serial monitor
 Serial.print("UID tag :");
 String content= "";
 byte letter;
 for (byte i = 0; i < mfrc522.uid.size; i++) // this reads the id of the card
 {
 Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
 Serial.print(mfrc522.uid.uidByte[i], DEC);
 content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
 content.concat(String(mfrc522.uid.uidByte[i], DEC)); 
 }
 String uidrf = content.substring(1); //this sets the card id to a variable

 Serial.println();
 Serial.print("! Signing into space - Timer Started !");
 content.toUpperCase();
 if (content.substring(1) == (Firebase.getString("Users/UID1")) || // this checks if the userid matches the database and the card.
  content.substring(1) == (Firebase.getString("Users/UID2")) || 
  content.substring(1) == (Firebase.getString("Users/UID3")) || 
  content.substring(1) == (Firebase.getString("Users/UID4"))|| 
  content.substring(1) == (Firebase.getString("Users/UID5"))) //change 
 here the UID of the card/cards that you want to give access
{
if (Firebase.getString("SpaceState/Space1") == "0"){
   Serial.println(" Parked sp1 ");
 Firebase.set("UsersInSpace/Space1" , uidrf); // here is where i want to set the value to the variable so in the database it can show what uid is in the space.
 Firebase.set("SpaceState/Space1" , "1");
  digitalWrite(4, HIGH);   // turn the LED on (HIGH is the voltage level)
 delay(1000);                       // wait for a second
 digitalWrite(4 , LOW);    // turn the LED off by making the voltage LOW
  delay(1000);
   }

Answer 1

您在3个不同的位置使用uidrf。

String uidrf;
content.substring(1) = uidrf;
Firebase.set("UsersInSpace/Space1" , uidrf);

首先，您声明变量，但未为其分配值（默认初始化）。

将content.substring(1)的值更改为uidrf将导致不确定的行为。我假设调用Firebase.set("UsersInSpace/Space1" , uidrf)时也会发生同样的情况。

您可能想做：

uidrf = content.substring(1);

但是您的问题目前尚不清楚。

如何将rfid卡中的传入数据设置为变量，以便可以将其设置为数据库中的空间ID？

1 个答案: