Question

我正在使用arduino和appinventor开发一个简单的RPM传感器。我遇到的问题是Android没有收到大于255的整数值或来自Arduino BT的大量垃圾。

arduino的逻辑已经很好了。它在16x2 LCD上正确显示RPM，精度很高。我也想通过蓝牙将RPM发送到具有appinventor界面的android。它工作但只显示最大值255。即使LCD显示1000+ RPM，在android上总是显示0到255之间。

我尝试使用类型转换（对char，并将其作为文本打印而不成功）。还更改了appinventor上的接收字节数（从1到4个字节）

Arduino的代码：

// include libraries
#include <LiquidCrystal.h>

const int resolution = 500;
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

//hardware global constants;
const int inputPin = 7;
const int ledPin = 13;
//const int bluetoothTx = 9;
//const int bluetoothRx = 8;

//logical variables
int inputState = 0;
int lastPinState;
int counter = 0;
int timeI = 0;
int timeF = 0;
int revolutions;
int cilinderRatio = 2;
int rpm = 0;
char * data = 0;
//---------------------------------------
//BLUETOOTH RESERVED

void setup() {
  //set up input Pin and integrated led (pin13)
  pinMode(inputPin, INPUT);
  pinMode(ledPin, OUTPUT);
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("RPM:");
  //Setup Bluetooth Serial Connection to Android
  //pinMode(bluetoothTx, OUTPUT);
  //pinMode(bluetoothRx, INPUT);
  Serial.begin(9600);

}

void loop() {
  rpm = 0;
  revolutions = 0;
  counter = 0;
  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  timeI = millis(); //get current running time
  do{
    //get current state
    inputState = digitalRead(inputPin);
    //if a pulse occurs, continues
    if(inputState == HIGH) {
    //if last state is not equal to last state, count it increasing 1 
    if(lastPinState != inputState)
    {
      counter += 1;
    }
  } 
  lastPinState = inputState; // takes current input State as last state
  timeF = millis(); //get final execution time
 }while((timeF - timeI) < resolution); //Repeat until reach resolution sample
 //lcd.print(counter); //Print how much pulses was counted
 // Revolutions is how much resolutions occured in one minute
 //since resolution is a seconds fraction, 1000mS * 60S must be
 //considered for RPMs 
 revolutions = counter * (60000 / resolution);
 //lcd.print(revolutions); //Print how much turns was counted, in fact
 //Revolutions divided by cilinderRatio is equal to RPM
 rpm = revolutions / cilinderRatio;
 rpm = rpm / 2;
 lcd.print(rpm); //Print Revolutions per minute
 lcd.print("                ");
 Serial.write(rpm);
 rpm = 0;
 counter = 0;
 digitalWrite(ledPin, LOW);
}

P.S。：我已经将接收到的字节更改为2来管理大于255的更好的整数。但是，它显示了很多垃圾超过255.

Answer 1

我通过分离每个字节来解决问题。

首先，定义了一个2字节类型的数据数组：

byte data[2];

然后在表达式中将rpm的每个字节放在一个字节中：

data[0] = (byte) rpm; //typecast of rpm integer to byte
data[0] = ((byte) rpm >> 8); //typecast and 8-bit shift

Answer 2

根据Arduino doc on Serial write http://arduino.cc/en/Serial/Write。 Serial.Write一次发送一个字节或一系列字节。因此，您需要将整数RPM转换为数字字符串使用itoa或类似的东西。

您也可以使用Serial.print（）代替直接将整数作为数字发送。

通过蓝牙+ Android + appinventor从Arduino接收大整数

2 个答案: