将HC-05模块连接到我的Arduino Nano（RX-TX和TX-RX，波特率9600）。模块以20 Hz的频率传输数据（手机上的RacaChrono应用程序读取的字符串）（频率可以更改）。
但是每5秒传输中有~0.3秒滞后。 数据和使用的计数器仍然传输，但有滞后。
以下是我用来从卡丁车收集数据并使用HC-05模块传输数据的所有代码：
/*
The code calculates the acceleration and brake pedals position, RPM, current gear, temperature and the laptime
*/
int rpm = 0, gear = 0, brake = 0, acceleration = 0, sensorValue1 = 0, sensorValue2 = 0;
unsigned long count = 0, lastmillis = 0;
volatile int half_revolutions = 0;
unsigned long debounceDelay = 200; // the debounce time;
unsigned long lastDebounceTime = 0; // the last time the gear was changed
unsigned long lastTransmit = 0; // the last time the $RC2 string was transmitted
int transmitRate = 50; // transmit the $RC2 string every * milliseconds
int RPMupdate = 100; // update the RPM counter every * milliseconds
String readString; // used in changing the settings with serial commands
/* variables of the laptimer */
float second = 1000; // 1000 milliseconds in a second
float lapTime = 0; // the variable that will be passed in the $RC string
long lapTimeDebounce = 1000; // how much time in milliseconds must pass before reading another pass over the line
long lapMillis = 0; // How long has it been since the last time the sensor was HIGH
long lapMillis2 = 0; // How long has it been since the last time the sensor was HIGH (for 2+ sectors)
int sectors = 1; // the number of split-lines
int line = 0; // the number of times you passed over the line
void setup(){
attachInterrupt(0, rpm_fan, RISING); // attach an interrupt on pin number 0 - physical pin No.2
Serial.begin(9600); // set the serial baudrate to 9600
pinMode(A0, INPUT); // acceleration
pinMode(A1, INPUT); // brake
pinMode(A3, INPUT); // temperature
pinMode(10, INPUT); // laptime
pinMode(11, INPUT); // gear +
pinMode(12, INPUT); // gear -
}
void loop(){
long ddd=millis();
while (Serial.available()) { // loop that runs only when serial data is receiver by the Arduino
delay(10);
if (Serial.available() > 0) {
char c = Serial.read(); //gets one byte from serial buffer
readString += c; //makes the string readString (1st byte + second byte + third byte + ...)
}
}
int a=readString[0]; // transforms the first byte received into an integer and stores it in the variable "a"
int b=readString[1];
int c=readString[2];
if (readString.length()>0) { // if there is something in the receiving serial of the Arduino
if (a==49 && b==49){gear=0;} //change the settings based on the numbers received
if (a==49 && b==50){gear=1;} // the numbers that a and b are compared to are the ASCII values of 1, 2, 3, 4 and 5
if (a==50 && b==49){sectors=1;}
if (a==50 && b==50){sectors=2;}
if (a==50 && b==51){sectors=3;}
if (a==50 && b==52){sectors=4;}
if (a==51 && b==49){RPMupdate=20;}
if (a==51 && b==50){RPMupdate=50;}
if (a==51 && b==51){RPMupdate=100;}
if (a==51 && b==52){RPMupdate=200;}
if (a==52 && b==49){transmitRate=20;}
if (a==52 && b==50){transmitRate=50;}
if (a==52 && b==51){transmitRate=100;}
if (a==52 && b==52){transmitRate=200;}
if (a==53 && b==49){debounceDelay=100;}
if (a==53 && b==50){debounceDelay=150;}
if (a==53 && b==51){debounceDelay=200;}
if (a==53 && b==52){debounceDelay=250;}
readString=""; // empties the string variable
}
if (sectors == 1){
if ((millis() - lapMillis) > lapTimeDebounce && digitalRead(10) == HIGH){ // if the lap time sensor is triggered and enough time has passed since the last trigger (for debounceing)
lapTime = time(); // calculate how many seconds have passed
lapMillis = millis(); //reset the last time the sensor was triggered
}
}
if (sectors > 1){
if ((millis() - lapMillis2) > lapTimeDebounce && digitalRead(10) == HIGH){// if the lap time sensor is triggered and enough time has passed since the last trigger (for debounceing)
line = line + 1; // a split line was crossed
if (line == (sectors +1)){ // if enough split lines have been crossed
lapTime = time(); // calculate how many seconds have passed since crossing the start/finish line
lapMillis = millis(); //reset the last time that the start/finish line was crossed
line = 0; // reset the split lines
}
lapMillis2 = millis(); // reset the last time that the sensor was triggered
}
}
if ((millis() - lastDebounceTime) > debounceDelay && digitalRead(11) == HIGH){ // if the gear+ sensor has been triggered and sufficient time has passed since last trigger
gear += 1;
if (gear>6){ // if you are in sixth gear and trigger the gear+ sensor the display remains 6
gear=6;
}
lastDebounceTime = millis();
}
if ((millis() - lastDebounceTime) > debounceDelay && digitalRead(12) == HIGH){
gear -= 1;
if (gear<1){ // if you are in first gear and trigger the gear- sensor the display remains 1
gear=1;
}
lastDebounceTime = millis(); // reset the time when the last gear was changed
}
/* //temperature reading
int reading = analogRead(2); // converting that reading to voltage, for 3.3v Arduino use 3.3
float voltage = reading * 5.0;
voltage /= 1024.0;
float temperatureC = (voltage - 0.5) * 100 ; //converting from 10 mv per degree wit 500 mV offset to degrees ((voltage - 500mV) times 100)
*/
sensorValue1 = analogRead(A0);
sensorValue2 = analogRead(A1);
acceleration = map(sensorValue1, 0, 1023, 0, 100); //maps the input value of 0-1023 to 0-100
brake = map(sensorValue2, 0, 1023, 0, 100); //maps the input value of 0-1023 to 0-100
if (millis() - lastmillis >= RPMupdate){ // Update every one hundredth of a second.
detachInterrupt(0); // Disable interrupt when calculating
rpm = half_revolutions * 60; // Convert frequency to RPM, note: this works for one interruption per full rotation. For two interrupts per full rotation use half_revolutions * 30.
half_revolutions = 0; // Restart the RPM counter
lastmillis = millis(); // Update lasmillis
attachInterrupt(0, rpm_fan, RISING); // enable interrupt
}
if (millis() - lastTransmit >= transmitRate) { // send the $RC2 string every *transmitRate* milliseconds
String buffer = "RC2,," + String(count) + ",,,," + rpm + "," + gear + "," + acceleration + "," + brake + /*"," + temperatureC + */"," + String(lapTime) + ",,,,,"; // construct the $RC2 string using the variables and accounting for the format RaceChrono asks for
String checksum = String (checkSum(buffer), HEX); // calculate the checksum of the RC2 string
char crc = checkSum (buffer);
String data = "$" + buffer + "*";
Serial.print (data);
if (crc<16){ // if the HEX value of the checksum is one character, add "0" in front
Serial.print ("0");
}
Serial.println (checksum);
if (count == 65535){
count = 0; // reset the counter variable when it reaches 65535 (the max value an int can hold)
}
else
count += 1; // increment the count variable
lastTransmit = millis(); // reset the time when the last $RC2 string was transmitted
}
}
/* function that calculates the NMEA checksum and returns the value */
char checkSum(String chars) {
char check = 0;
for (int c = 0; c < chars.length(); c++) {
check = char(check ^ chars.charAt(c));
}
return check;
}
/* function for the RPM counter */
void rpm_fan(){
half_revolutions++;
}
/* function for the timer */
float time(){
long timeNow = (millis() - lapMillis); // calculate how many milliseconds took to do a lap
float seconds = timeNow / second; // calculate how many seconds (with decimals) is the amount of milliseconds
return seconds; // return the value as a float
}
以下是输出的示例：
$RC2,,1,,,,0,0,83,30,0.00,,,,,*28
$RC2,,2,,,,0,0,83,30,0.00,,,,,*2b
$RC2,,3,,,,0,0,83,30,0.00,,,,,*2a
$RC2,,4,,,,0,0,83,30,0.00,,,,,*2d
$RC2,,5,,,,0,0,83,30,0.00,,,,,*2c
$RC2,,6,,,,0,0,83,30,0.00,,,,,*2f
$RC2,,7,,,,0,0,83,30,0.00,,,,,*2e
$RC2之后的第一个数字是计数器。 （每次迭代都会传输，但每隔5秒就有一些延迟）
延迟导致应用程序误读某些数据（因为传输速率从20 Hz降至19.1-19.4 Hz）
任何人都可以看到导致此延迟的问题吗？
此外，如果您有改进代码的建议，我非常乐意实施它们。