I'm able to send some characters in blue tooth to my android device.
But after scanning my finger and send the finger.fingerID value to android device,
Only a special character was sent.
So it came to me that the value is Integer and tried to convert it to character but still getting some error.
When I run my code here, I immediately getting back to void setup();
int getFingerprintIDez() {
uint8_t p = finger.getImage();
if (p != FINGERPRINT_OK) return -1;
p = finger.image2Tz();
if (p != FINGERPRINT_OK) return -1;
p = finger.fingerFastSearch();
if (p != FINGERPRINT_OK) return -1;
// found a match!
Serial.print("Found ID #"); Serial.print(finger.fingerID);
Serial.print(" with confidence of "); Serial.println(finger.confidence);
String toStr;
char toChar[2];
toStr=String(finger.fingerID);
toStr.toCharArray(toChar, toStr.length());
BTSerial.write(toChar);
Serial.print(toChar);
return finger.fingerID;
}
Your toChar buffer is too small for a string that could possibly be 5 characters long. You should allocate 10 bytes instead, more than enough to hold any result.
toCharArray does not null-terminate the string so even if write() accepts null-terminated strings alone (it doesn't), it would run off the end of the string looking for a null. write() accepts either a single character or a pointer to a char array and the number of characters to be written.
You don't need to go through all this hassle; merely call:
BT.print(finger.fingerID);
And the built-in Print class will handle the conversion messiness for you.
Related
I'm desperatly trying to get arduino to divide a string from processing into two sets of variables. In the code below I've decided to just type the important parts but x and y does of course contain the correct values. Any solution would be appreciated. These are my two attempts so far:
Attempt 1 doesn't work at all.
1.Processing:
myPort.write(x + "," + y + "\n");
1.Arduino:
String tempX = Serial.readStringUntil(44);
String tempY = Serial.readStringUntil(10);
String x = tempX.substring(0,tempX.length() -1);
String y = tempY.substring(0,tempY.length() -1);
Attempt 2 where x works correctly but not y.
2.Processing:
String [] dataToSend = new String [2];
dataToSend [0] = x;
dataToSend [1] = y;
String joinedData = join(dataToSend, ":");
myPort.write(joinedData);
2.Arduino:
String x = Serial.readStringUntil(":");
Serial.read(); //next character is comma, so skip it using this
String y = Serial.readStringUntil('\0');
First, don't worry about combining them on the Processing side. Sending two strings one right after the other is the same as sending one long string. It's all being broken into bytes on the Serial line and nobody can tell where one print line stops and the next starts.
myport.write(x);
myport.write(',');
myport.write(y);
myport.write('\n')
will work just as good.
Then on the Arduino side you most likely want to shy away from the String class. Read the data character by character into a char array.
char myArray[howLongTheStringIs];
char x[howLongXIs];
char y[howLongYIs];
int index = 0;
This gets called over and over in loop and picks up serial data as it comes in:
while (Serial.available()){
char c = Serial.read();
myArray[index] = c; // add c to the string
myArray[++index] = 0; // null terminate our string
if(c == '\n'){ // if we are at the end of the string
handleString();
}
}
Then you have a function to parse your string there are lots of ways to do that:
If you don't know anything about the strings other than the separator use strtok:
void handleString(){
char* ptr = strtok(myArray, ":"); // get up to the ":" from the string
strcpy(x, ptr); // copy into x
ptr = strtok(NULL, "\n"); // get from the separator last time up to the next "\n"
strcpy(y, ptr); // copy into y
index = 0 // reset our index and
myArray[0] = 0; // and clear the string
}
That's all untested and uncompiled and written in the reply box, so if I made a little typo in there please forgive and correct. But something like this should work. If you already know the exact lengths of the strings (or can send them from the processing code) then the handleString method can be simpler. If you've got something short to do with x and y and don't need them after that then maybe you can just keep pointers to where they are in myArray. It all depends on what the larger picture goal of your code is. But something like this should get the job done.
I want to print my string variable using printf method:
id = 6415F1BF713C
Serial.printf("id: %s\n\n", id);
Serial.print(id);
The result that I got was:
id: ⸮⸮⸮?
6415F1BF713C
is there any thing that's wrong?
Thanks.
Update :
//get device id
String getDeviceID() {
uint64_t chipid = ESP.getEfuseMac(); // The chip ID is essentially its MAC address(length: 6 bytes).
uint16_t chip = (uint16_t)(chipid >> 32);
char devID[40];
snprintf(devID, 40, "%04X%08X", chip, (uint32_t)chipid);
return devID;
}
String id = getDeviceID();
Serial.printf("id: %s\n\n", id);
Serial.print(id);
You didn't offer enough code to properly debug this, but I'm guessing what you mean is
String id = "6415F1BF713C";
Serial.printf("id: %s\n\n", id);
Serial.print(id);
The %s format in the printf() method expects to take a C/C++ char *, not a String. When you passed it a String, it printed the memory address of the String object - four characters which would appear as garbage, as you saw.
C and C++ use char * (pointers to characters) and char [] (arrays of characters) to represent strings. These are different from the Arduino String class, and people often confuse them.
To use the printf() method with a String you need to get its C string pointer, like this:
Serial.printf("id: %s\n\n", id.c_str());
The reason that this:
Serial.print(id);
works is that the print() method has a form that specifically expects to take a String object as an argument.
I'm using an android app to send values to control servos.
Code:
char inputData[4];
char buffer[3];
void loop()
{
if(Serial.available() > 3) {
for (int i = 0; i < 4; i++){
inputData[i] = Serial.read();
}
char buffer[4];
buffer[0] = inputData[1];
buffer[1] = inputData[2];
buffer[2] = inputData[3];
buffer[3] = '\0';
int angle = atoi(buffer);
Serial.write(angle);
}
}
Issue: I'm getting the values + A-F letters to address each servo - A10, A180, B30 etc. Now the trouble is turning this to an actual integer. As you can see I've declared a character array to store the integers in and as suggested in a post on the arduino forum, I added a \0 at the end of the array. Currently, the Atoi returns random characters, mostly squares and some random numbers. I've tried even assigning them to a string and then .toInt() but same issue there, mostly squares.
Any ideas?
Thanks!
Use print or println to see the number as text. write sends it as byte and Serial Monitor shows a symbol with that ASCII code.
I am trying to create a software lighting desk by using Qt and Arduino with a DMX Shield. I've been able to establish communication between these two and can send commands over to Arduino Mega (at the moment the communication goes only one way). I am periodically (every 200 ms) sending values of 11 faders to Mega as a String.
eg.: A123 B234 C050 ... J222 M255
The values in the string above are variables based on the position of the sliders and should be used to adjust the values of light intensities saved into each fader on the Mega side. The Letters in each section identify corresponding fader. A = fader1, B = fader2, ... Just for clarity: I can bring up a light/s at a specific intensity -> these intensities are then assigned to a fader and when that fader is moved I want these values to adjust and be sent out to the actual lights/dimmers. The calculations work fine but my Mega would eventually become unresponsive.
I think my problem is parsing the incoming string. I have tried the strtok() method and readStringUntil() to no avail. It is also difficult to monitor the incoming strings in Serial Monitor as this is used for the communication with Qt.
Would be happy for any kind of help. Please ask questions if anything is unclear.
Edit:
This is one of my attempts at solutions
const char delim[2] = " ";
char *token;
if(Serial.available())
{
//incomingMessage = Serial.readString();
incomingMessage = Serial.readStringUntil("\n"); // read the whole string until newline
//Serial.println(incomingMessage);
const char* str = incomingMessage.c_str(); // convert it to a C String terminated by a null character "\0"
//Serial.println(str);
token = strtok(str, delim); // first part is a first section until delimiter occurs "-space- "
//Serial.println(token);
LX_Rated.commandLineResolve(token); // resolve it
while( token != NULL ) { // continue splitting and resolving the incoming message until it reaches the end
token = strtok(NULL, delim);
LX_Rated.commandLineResolve(token);
}
}
Edit2:
I have confirmed that I receive the whole string sent by Qt. When I try to tokenise it using the strtok() function and print out the first token I get back the whole string, the other tokens are empty. I don't see any mistake in my code here. I even tried to slow down the sending of the string from Qt to one per 5 sec. Does anybody have any idea what is going on? I don't see why this standard function doesn't work as expected. Please see the amended code below.
if(Serial.available()) {
incomingMessage = Serial.readStringUntil("\n");
Serial.println("ok");
Serial.flush();
char* nullTerminatedIncomingMessage = incomingMessage.c_str();
const char delimiter = " ";
char* token;
char* token1;
char* token2;
//char* secondToken;
token = strtok(nullTerminatedIncomingMessage, delimiter);
token1 = strtok(NULL, delimiter);
token2 = strtok(NULL, delimiter);
Serial.println(token); // print the first section
//Serial.println(incomingMessage);
Serial.flush();
Serial.println(token1);
Serial.flush();
Serial.println(token2);
Serial.flush();
//while(token != NULL)
// secondToken = strtok(NULL, delimiter);
//Serial.println(secondToken);
//Serial.flush();
incomingMessage = "";
}
Your mistake - at the very least - is in assuming that all the input is available when you expect it. You need to defer processing until an entire line has been assembled. Serial.readStringUntil blocks until an entire line is available, and that's not what you expect. You essentially need to replace Serial.available() with Serial.lineAvailable(), except the latter is not implemented.
This answer contains a complete solution to your issue - including both Qt and Arduino code - and an Arudino emulation layer. It might be a good starting point, especially that you can easily co-debug both Qt and Arduino projects from within one application and using one debugger!
As for difficulty in monitoring communication, you can(in Qt) dump everything you read into console and do the same for everything you write into the serial port. It will show in the console tab of QtCreator
#include <QDebug>
...
qDebug() << "whatever" << endl;
Aso for parsing the data you read from to serial port, take a look at this to see how to easily split the sliders info into individual strings(with QRegExp)
How Can I Split a String According To Delimiters in Qt?
I can't possibly guess why your arduino would be unresponsive without the code.
EDIT:
Is it possible, when you generate the string in Qt, that you separate the tokens by something other than space? Maybe tab("\t") or something? strtok accepts multiple delimiters in the delimiter string, may be something to try.
If that is not the case, there is the unlikely possibility that something's wrong with the strtok(...) function(btw. it modifies the original string, that in itself could be a problem). Also, strtok could return a NULL pointer, you don't seem to handle that case(some wrong input - print a message). You could try this as an alternative to normal strtok:
/**
* #brief custom strtok replacement with the same interface
* It does not modify the original string
* Token length is limited to 63 characters
* #param ptr pointer to the string or NULL
* #param delim delimiting character(only the first character will be used)
*/
const char * my_strtok(const char * ptr, const char * delim) {
// Persistent variables, it will remember pointer to the processed string
static const char * src;
static char buffer[64]; // Token is limited to 63 characters
if(ptr) { // Remember the pointer, if a new one was supplied
src = ptr;
}
if(src == NULL || *src == '\0')// Invalid / empty string / no next token - return NULL
return NULL;
char i = 0;
for(i = 0; i < 63 && *src != delim[0]; i++) {// Copy token until delimiter or end of buffer
buffer[i] = *(src++);
}
if(*src == delim[0]) // Skip over the delimiter to the begining of the next token
++src;
buffer[i] = '\0'; // Any returned string must be terminated
return buffer;
}
#include <cstdlib>
#include <cstring>
#include <cassert>
void test() {
const char * str1 = "123 456 asdf jkl;";
assert(strcmp("123", my_strtok(str1, " ")) == 0);
assert(strcmp("456", my_strtok(NULL, " ")) == 0);
assert(strcmp("asdf", my_strtok(NULL, " ")) == 0);
assert(strcmp("jkl;", my_strtok(NULL, " ")) == 0);
assert(NULL == my_strtok(NULL, " "));
assert(NULL == my_strtok(NULL, " "));
assert(strcmp("123", my_strtok(str1, " ")) == 0);
}
I'm trying to read variable streams of characters and process them on the Arduino once a certain string of bytes is read on the Arduino. I have a sample sketch like the following, but I can't figure out how to compare the "readString" to process something on the Arduino. I would like the Arduino to process "commands" such as {blink}, {open_valve}, {close_valve}, etc.
// Serial - read bytes into string variable for string
String readString;
// Arduino serial read - example
int incomingByte;
// flow_A LED
int led = 4;
void setup() {
Serial.begin(2400); // Open serial port and set Baud rate to 2400.
Serial.write("Power on test");
}
void loop() {
while (Serial.available()) {
delay(10);
if (Serial.available() > 0) {
char c = Serial.read(); // Gets one byte from serial buffer
readString += c; // Makes the string readString
}
}
if (readString.length() > 0) {
Serial.println( readString); // See what was received
}
if (readString == '{blink_Flow_A}') {
digitalWrite(led, HIGH); // Turn the LED on (HIGH is the voltage level).
delay(1000); // Wait for one second.
digitalWrite(led, LOW); // Turn the LED off by making the voltage LOW.
delay(1000); // Wait for a second.
}
Some definitions first:
SOP = Start Of Packet (in your case, an opening brace)
EOP = End Of Packet (in your case, a closing brace)
PAYLOAD = the characters between SOP and EOP
PACKET = SOP + PAYLOAD + EOP
Example:
PACKET= {Abc}
SOP = {
EOP = }
PAYLOAD = Abc
Your code should process one character at a time, and should be structured as a state machine.
When the code starts, the parser state is "I'm waiting for the SOP character". While in this state, you throw away every character you receive unless it's equal to SOP.
When you find you received a SOP char, you change the parser state to "I'm receiving the payload". You store every character from now on into a buffer, until you either see an EOP character or exhaust the buffer (more on this in a moment). If you see the EOP char, you "close" the buffer by appending a NULL character (i.e. 0x00) so that it becomes a standard NULL-terminated C-string, and you can work on it with the standard functions (strcmp, strstr, strchr, etc.).
At this point you pass the buffer to a "process()" function, which executes the operation specified by the payload (1)
You have to specify the maximum length of a packet, and size the receive buffer accordingly. You also have to keep track of the current payload length during the "payload receive" state, so you don't accidentally try to store more payload bytes into the temporary buffer than it can hold (otherwise you get memory corruption).
If you fill the receive buffer without seeing an EOP character, then that packet is either malformed (too long) or a transmission error changed the EOP character into something else. In either case you should discard the buffer contents and go back to "Waiting for SOP" state.
Depending on the protocol design, you could send an error code to the PC so the person typing at the terminal or the software on that side knows the last command it sent was invalid or not received correctly.
Finally, the blink code in you snipped should be replaced by non-blocking "blink-without-delay"-style code (look at the example that come with the Arduino IDE).
(1) Example of a "process" function:
void process(char* cmd) {
if (strcmp(cmd, "open_valve") == 0) {
open_valve();
}
else if (strcmp(cmd, "close_valve") == 0) {
close_valve();
}
else {
print_error("Unrecognized command.");
}
}
It seems you are comparing the string in this statement:
if( readString == '{blink_Flow_A}' )
So I don't get your question re :
but I can't figure out how to compare the "readString" to process something
Are you really asking:
How do I extract the commands from an incoming stream of characters?
If that is the case then treat each command as a "packet". The packet is enclosed in brackets: {}. Knowing that the {} brackets are start and end of a packet, it is easy to write a routine to get at the command in the packet.
Once the command is extracted just go through a if-then-else statement to do what each command is supposed to do.
If I totally misunderstood your question I apologize :)
EDIT:
see http://arduino.cc/en/Tutorial/StringComparisonOperators
if( readString == "{blink_Flow_A}" ) should be correct syntax.
Since you have a statement
Serial.println( readString);
you should see the string received.