When I use the Serial.read() function and obtain a character "a" or "s" from the serial monitor I can verify that the stored character is indeed the one I typed. Next the char is converted to string which I verified is still the same letter I typed by printing in the serial monitor. Then, when I try to use an if statement to check whether the string is "a" or "s" for some reason it never goes into either of the if statements. I added Serial print in the two if statements but they never get displayed. Please help, thank you!
I changed the code a bit for simplicity and removed irrelevant parts to the question.
#include<Servo.h>
String readString;
void setup()
{
Serial.begin(9600);
}
void loop()
{
while (Serial.available()) {
char c = Serial.read(); //gets one byte from serial buffer
readString += c; //makes the string readString
delay(2); //slow looping to allow buffer to fill with next character
Serial.print("readstring value:");
Serial.print(readString);
}
if (readString.length() >0) {
if(readString == "a"){
Serial.print("equal a ");
//increment motor
}
if (readString == "s"){
Serial.print("equal s ");
//decrement motor
}
}
readString=""; //empty for next input
}
//https://forum.arduino.cc/index.php?topic=733454.0
// modified from
// readOneChar.ino
// Reads one char cmds from Serial
// https://www.forward.com.au/pfod/ArduinoProgramming/SoftwareSolutions/index.html
// Pros: Extremely Simple, Non-blocking and Robust
// Cons: Nothing really. You can do a lot with 52 one char cmds (A..Z,a..z)
void setup() {
Serial.begin(9600);
for (int i = 10; i > 0; i--) {
Serial.print(' '); Serial.print(i);
delay(500);
}
Serial.println();
}
void loop() {
char c = Serial.read(); // note read() returns an int, char c = converts it to a char
if (c != -1) { // read() return -1 if there is nothing to be read.
// got a char handle it
Serial.println(c);
if (c == 'a') {
Serial.println("inc");
//increment motor
} else if (c == 's') {
//decrement motor
Serial.println("dec");
}
}
}
For reading a String try this code
This will return the input line when '\n' found OR if no more input for 1sec (non-blocking)
so works with \r\n and \n line endings and also No line ending
// readStringUntilLimitedTimeout.ino
// Reads chars into a String until newline '\n'
// https://www.forward.com.au/pfod/ArduinoProgramming/SoftwareSolutions/index.html
// Pros: Simple. Non-Blocking, Robust against unexpectedly long input lines and missing termination, until_c char
// Cons: Nothing really.
String input;
void setup() {
Serial.begin(9600);
for (int i = 10; i > 0; i--) {
Serial.print(' '); Serial.print(i);
delay(500);
}
Serial.println();
Serial.println(F("readStringUntilLimitedTimeout.ino"));
input.reserve(20); // expected line size
}
// read Serial until until_c char found or limit char read or timeout, returns true when found/limited else false
// non-blocking, until_c, if found, is returned as last char in String, updates input String with chars read
bool readStringUntil(String& input, char until_c, size_t char_limit) { // call with char_limit == 0 for no limit
static bool timerRunning; static unsigned long timerStart; // timeout static variables
static const unsigned long timeout_mS = 1000; // 1sec set to 0 for no timeout
while (Serial.available()) {
timerRunning = false; // set true below if don't return first
char c = Serial.read();
input += c;
if (c == until_c) {
return true;
}
if (char_limit && (input.length() >= char_limit)) {
return true;
}
// restart timer running
if (timeout_mS > 0) { // only start if we have a non-zero timeout
timerRunning = true;
timerStart = millis();
}
}
if (timerRunning && ((millis() - timerStart) > timeout_mS)) {
timerRunning = false;
return true;
}
return false;
}
char terminatingChar = '\n';
void loop() {
if (readStringUntil(input, terminatingChar, 20)) { // read until find newline or have read 20 chars, use 0 for unlimited no chars
if (input.lastIndexOf(terminatingChar) >= 0) { // could also use check if (input[input.length()-1] == terminatingChar) {
Serial.print(F(" got a line of input '")); Serial.print(input); Serial.println("'");
} else {
Serial.print(F(" reached limit or timeout without newline '")); Serial.print(input); Serial.println("'");
}
input = ""; // clear after processing for next line
}
}
