Arduino function return string array. Ask Question Asked 10 years ago.
Arduino function return string array Here is an explanation of why Strings are evil. May 3, 2013 · I have a string String the_text = "Hello" and a function for each letter. A possibility is to convert the char array into a String I would expect, but that is not memory efficient I would expect. Aug 18, 2019 · char char_array[str_len]; is local to the function - it is created on function entry and its memory is released on function exit. I have written a function to do that: String printDigits(int digits) { String str Aug 1, 2017 · I was working with the String objet on all my projects. com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon. May 19, 2020 · This program requires me to read an sd card that contains a bunch of folders, I then need to save the names of each folder into an array. With return String(baseMacChr);, baseMacChr does not go out of scope conceptually until the closing } of the function getMacAddress, so that too is safe. The function call is made: names[3] = process_keys(14, 0); //don't want user to use up the 15th position The function is structured like this: char 3 days ago · I'm new but trying to learn. It returns a binary (not decimal) floating point number. begin(9600); } // Returning Aug 26, 2012 · It depends on what else you are doing. Right now I'm having to manually count how many elements I have in each array so I can set the upper limit for the random number generator. substring (from, to) Parameters. For example: `String myStrings[3];` How do I access specific elements in an array? Elements in arrays are accessed using their index numbers. May 29, 2017 · Well, your worst misconception is thinking that C allows you to pass a complete array as parameter or return value. Nov 2, 2007 · Hi, I am new to C and am trying to write a function which accepts no input parameters, but returns either a byte array or two separate byte variables, whatever will work. But fixing them will make you a better programmer. You can have the caller provide the buffer that will be used to store the return value: while(maxBufferSize && *buf = getByteFromSerial()) { //assumes getByte returns 0 for done Apr 30, 2017 · Functions can not return arrays. May 14, 2024 · Terminate a function and return a value from a function to the calling function, if desired. I'm not sure if this is done with pointers, I wasn't sure. So I wrote the main loop which prints out a message. Regards, Ray L. println(returnButtonLetter Sep 26, 2023 · Normally I would pass a pointer to an array, have the function operate on that and have my array done if the function does not return a 0. Aug 16, 2021 · Such as integers addr. In either case, how to limit Serial. Oct 8, 2017 · If your program has 50 functions in it, a global data definition means that any one of those functions could have a statement in it that affects the content of the array. An array of chars can, if null terminated, be used as a C string, but it is not a String object. I'm looking for ideas on how to get the 'RunColors' function to return 2 values. Dec 4, 2012 · Strings are evil. You need it so you can use any number of dimensions, or any data type you want. h> // For C // or #include <cstdlib> // For C++ // Allocate memory for a single element or an array void * malloc (size_t size); Sep 24, 2022 · You can return a pointer to a static buffer, of course. I tried using this code but it doesn't convert with the "0x" at the begining, plus the array is inverted. nl, Amazon. . read() to read only 8 chars? (If loop with string. Kindly, go through my code and let me Feb 7, 2014 · Even though the return type is a string array: public String[] allWordsWith (char letter){ You need to return an array, as allWordsWith implies you want multiple values. strstr () will search for a substring and return a pointer to it (if found, null otherwise). So, your function call needs to get at least two parameters. Remember the Arduino has just 2KB of RAM! Here is a function you can use to make that conversion using the strtoul() function: Apr 17, 2021 · All types of array. You wouldn't say println(*string), right? I am not sure where you stored your array, but it wasn't in string. Here is the relevant part of the code: float ChToCoord (int ChA_T, int ChB_T, int ChA_S, int ChB_S, int ChA_Z Mar 2, 2017 · Hi! I am a beginner at Arduino Programming. Jun 30, 2016 · I would like to define an array so that I could pass that array (of 5 numbers in this instance) to a function that I have defined. If you really want an array of strings then declare an array of strings like String array[50]; There was also a a problem that sometime you split the name by comma, sometime by space, and sometime by comma+space. Apr 10, 2020 · I would avoid passing strings' array as a reference. toCharArray(char_array, str_len); Dec 5, 2019 · The user will send a text string to the interpreter and it will do stuff and return an integer (either data or a code depending on what the user requested). is between 0x80000 to 0x9ffff and also for string's addr is between 0 to 0x1ffff. ca, Amazon. Sep 1, 2012 · In a project i'm making, i need to use arrays. You are writing a pointer into the locations just after string, which will bite you in the butt someday. Jan 28, 2016 · Using Arduino F() Macro with string arrays. I thought I could use sizeof() but that just returns the number of bytes, not the number Aug 1, 2017 · If you are writing to the global str, there is no reason for the return, and in fact, I don't know what this is going to do: str[3] = text(2); since str[3] does not even exist. This doesn't answer the question either if the question is about how to implement the very same that Java would do. If you have large enough data that needs to be read as char arrays i would suggest serialization instead. Ask Question Asked 10 years ago. They are defined as: String myName; char yourName[15]; As you might guess, Strings come with a lot of methods just like C# (e. se Jun 13, 2011 · Hi! I'm writing a program for Arduino, and I have a function which takes values from a few input functions, does some math and supposed to giva an array of x, y, z coordinates. fr, Amazon. Recently, I finished an WS2821B LED string sketch and am finding that C++ doesn't return more than 1 value from a function. String rw_ssid = ""; String rw_pswd = ""; const int keys = 2; String read_ssid_pswd [keys]; if (EEPROM. I didn’t code the generic function, since here is Mar 17, 2016 · Lots of ways to parse a captured character strings. The called function will then fill the array and only return a success/fail value. The way of declaring the array of string. Also, an array of chars can be used to instantiate a String object, like this: Apr 25, 2013 · _string is already a pointer, so you don't need to dereference it. By passing the array to a function as a function parameter, as shown in westfw's first example, you remove the other 49 functions from the list of functions that can affect To pass an element of an array to a function, use the subscripted name of the array element as an argument in the function call. substring (from) myString. About six months ago, I swore off using the String class and coding exclusively with char strings. Aug 16, 2021 · I am trying to make several calls to a function that returns a char array and have the returned char array assigned to a second char array. ) Use void if no return. Either return a struct, or pass by reference and modify in the function. void loop(){ white[10 These are required for your function, assignment, and return to work: The array declared in the calling sub has to be of undeclared length. The number of strings and the size of the strings can change. and then back to an array in my void loop(). May 31, 2020 · My read function returns an array of strings. I tried using a struct, tried the array method (above), tried to pass my local struct or array as a parameter, tried to get the data as a return value nothing works. You cannot assign one to the other. But unfortunately there is an over flow. You can read more about working with C strings here. Feb 4, 2017 · Hi all, I’d basically need to develop a generic function to get the length of an array of string that is passed as parameter to a function. Jul 5, 2022 · Hello! I am trying to convert a String to an array of HEX. Nothing with a percent sign to replace means nothing in that string gets replaced and you just end up with the string "Custom". I'd prefer to do it this way, as it's going to get moved into a library, and I think it'd be "cleaned" to do it like this, as opposed to have the function modify a global array. Whenever possible, use character arrays (char *). Jul 27, 2020 · When you declare int array[50]; you declare an array of numbers so only numbers can be stored inside it. Ok so far. ) ; and i would like to create a function that returns this structure : ActualSpeed Readspeed(void) { code t May 31, 2022 · Is there a way to send a char array into a function? I made my own function in order to rearrange a 1-dimensional char array but i did it by turning the char array into a String in my void loop() and then back into an array in my own function. The problem of string corruption should be that my sketch seems to use more than 2KB of ram. I need to send that string to another function, which accepts a char Array. only up to 2 decimal places. print Aug 11, 2023 · If you want to find the character 'X' in an array of chars, by hand, you can use a for loop to see if the character at an index i is equal to the character you are looking for. Can anyone confirm that you cant pass a char array to a function except via reference (char*)? Also can you return a char array from a function or do you have to include the array you want to return through a referenced array in the parameters? so I cant do Jun 25, 2019 · PieterP: The angle bracket syntax < > is used for templates. So I wrote this small helper function: char* ConvertStringToCharArray(String S) { int ArrayLength =S. Conceptually though, the code does what you ask. For example 1:2 as time. ArduinoGetStarted. The code that I wrote is shown below: #define SIZE 10 void setup() { Serial. Example Code. In this example the data string uses a comma "," to separate the data parts and a "*" to mark the end of the total data packet. h> #define PIN 5 # Mar 29, 2013 · A String is a class. What I have works Jan 5, 2016 · I have several strings stored in char arrays. Unfortunately you are returning a pointer to a local variable in the function which means that it is a pointer to undefined data as soon as the function returns. It can be a pointer, a class instance, or a struct. I've heard that using Char Arrays uses a lot less memory than using String Arrays. What should I do: Define input as char text[8]. The following subroutine performs the conversion from String to Char array. Now i have a question: Is there a way to find a value's index just by searching for the value? For example: int arrayVals[] = {2, 4, -8, 3, 5, 1}; Now for example when i input "-8" into a function, i need it to return the index of -8, which is 2. Oct 10, 2018 · I am working with a RFID scanner (RC522) and I want to store the Card and Tag UID's in an array and then when I scan the card check the array for the matching UID if there is a match it shows a message of unlocked if no match it shows message of denied. If you want to return the string array, you have to reserve it dynamically: Apr 11, 2020 · Hi everyone I have a project that generates random sentences. So I thought I would pass a pointer, allocate the size in the function and then return the length. I just want to confirm Ive read the reference and docs properly. Sep 24, 2022 · You will not need a return value then (as the return value is in the buffer argument). Nov 5, 2021 · Arduino: How to return Char Array Value in Arduino IDE Function?Helpful? Please support me on Patreon: https://www. When we say 'inside' we mean inside the curly-braces {} which come after the function name. Your code in reply #3 tried to put this function inside the loop() function and didn't correctly copy-paste the code that guix wrote. You try to return a pointer to char, which will point to a non-valid memory location. it looks easier for the people who is new to Arduino, it is however could caused Sep 19, 2013 · The following line is invalid: lat = readEEPROM(rom,0x0008); 'lat[]' is a character array. 1 Like Jan 9, 2017 · I have a GPS that is spitting out strings of data, might look something like this: String myString = "99,500,,45,W,5"; I'm trying to write a function that will extract a term from the string and return it e. Jun 10, 2011 · As the array has a maximum length of the char array is set to 255 a public variable need not to be dynamic, but as my code gets bigger I try to avoid public variables because otherwise the code gets too confusing. However, I'm having trouble with some code I wrote for myself as a proof of concept. g. If you want to use dynamic arrays please read the discussion carefully and do NOT start before reading the end. I planned on having the values passed back using a json string over serial so I added ArduinoJson to the Mar 28, 2014 · Make a global array and just have the function do whatever it does to the array. Jul 28, 2014 · I am trying to make a for loop run only for the number of strings there are in an array. g int hash(str) { return str[0]*20 + strlen(str); } // uses first and length to have a unique value silently assumes no string is longer than 20 Jan 31, 2012 · This function returns a single string separated by a predefined character at a given index. An other way would be to return a string and re-convert it into a char array, but this isnt nice either Dec 27, 2023 · A return function in Arduino, as the name suggests, is used to return a value from a function back to the calling routine. i. com May 12, 2011 · Hi all I'm trying to write some basic code where a function returns an array - or rather returns a pointer to the array. Ray In short, either declare an array of String objects: String myArray[length]; myArray[0] = String("text"); return myArray; or use an array of C-strings, i. com/roelvandepaarWith thanks & praise to God, and with th Apr 16, 2024 · Since they are not equal, the equals() function returns false and the message “Access denied!” is printed. Nov 8, 2024 · The Arduino programming language Reference, organized into Functions, Variable and Constant, and Structure keywords. h library. However, changing the function to return a char* will not really get you anywhere as returning the address of a string (char array) on the stack is a dangerous game - once the function has returned you can't rely on this pointer being valid. Oct 14, 2016 · int *function() { int array[3]; array[0] = 19; array[1] = 7; array[2] = 69; return array; } This may work, or not, depending on the surrounding code, on how the optimizer processes your program, and on how lucky you are when you test it. Use the power of C, pass a pointer to an array, which you will dynamically allocate. Nov 22, 2017 · I get an unpredicted behaviour of a program while trying to fill a dynamic array of String objects. Also: if you are using string constants you should learn about progmem. Arduino String Character Arrays, often referred to simply as character arrays or C-style strings, are sequences of characters stored in contiguous memory locations. String() - Arduino Reference This page is also available in 3 other languages May 26, 2012 · Like in how can I give a 2D array to a function which then returns a (changed) 2D array as a return value? A function can not return an array. Below is the basics of what I have so far. print(123, HEX)""" is not helping me cause I need to work with this May 16, 2016 · I'm working on a arduino mini/leonardo project to set up a USB connected Leonardo on a pi to monitor it's power source (a solar charged battery pack). lenght == 8 )? or is there a more efficient way? Dec 11, 2021 · WARNING: This is an attempt to clarify if there is any safe way to use dynamic arrays on Arduino Platform ! The recommended way often is to avoid dynamic memory allocation due to the missing memory manager who would clean up SRAM after the memory space is freed again. strcat, along with many other str* functions, returns the SAME pointer passed to it as the first argument, as a convenience, to make it easier to "chain" the result to another str* function. Anywho, what you are probably looking for is Serial. I have non-OOP code to capture serial strings, save them, and parse them. Then I wrote a function which gets a char argument and returns a simple string. This code doesn't provide the garbage collection Java provides, the strings are not unicode, etc. I am unable to get the correct output. What I am trying to do is write a function that will return a value. Don't use them. How to pass string to function in Arduino? ArduinoGetStarted. Better output the two strings separately thus avoiding unnecessary use of RAM. To quickly recap: strcpy() copies a source string into a destination buffer ; Watch for buffer overflows and size your destination safely; Proper use of strcpy() can optimize memory usage for string arrays Sep 14, 2020 · I am trying another bit of OOP with a class for reading and parsing serial input strings, such as GPS output. Thus you cannot simply return an array, that was created inside the function (outside of dynamic allocation). My output is supposed to show the array values mentioned as "from-to". Why is it so difficult to convert the macStr[18] to a String and Feb 5, 2016 · You might run into trouble when your programs get bigger and you start using lots of strings. Pass a pointer to an array of pointers and fill that with pointers to the portions of the string you have sliced. Regards. Pass a pointer to the array to be modified, and let the function modify the pointed-to array. Never use. es, Amazon. e ssid and password. You have to use Dec 27, 2019 · Hey Guys, i have a problem converting a string to an int array. begin(9600)… Nov 11, 2017 · Check out the functions in the string. After that, I need to display the names on a screen and allow the user to scroll through them and select them. Edit: I just tested, returning NULL/nullptr in strcmp function on Arduino does not crash, but crashes on ESP8266. ) that are easy to use, but horribly wasteful of memory. May 15, 2012 · Hi, I want to make a function that returns an array. Personally I would stay away from the String class, unless it is being used only occasionally. Feb 4, 2016 · You can't return more than one value from a function in C. Surely you'd just do return x? You have a few options. Jul 22, 2014 · Now I want this function to return this string (stored in variable x) to main function from where it has been called. The 'sizeof' preprocessor directive is handy for this. Dec 1, 2008 · Dear all, Just a quick question about passing char arrays to functions. println(F("This string will be stored in flash memory")); to be supported since Arduino 1. The string can contain any number of delimiters. The following works for me (copied and pasted from tutorial): const char string_0[] PROGMEM = "String 0"; const char string_1[] PROGMEM = "String 1"; const char string_2[] … Dec 27, 2023 · By now you should have a solid grasp of how to leverage the strcpy() function in your Arduino code for flawless string copying. Here's my code: void setup() { Serial. Mar 17, 2016 · Lots of ways to parse a captured character strings. value: Allowed data types: any variable or constant type. Either make this variable static, or use a global variable, or add another parameter to the function, which will be a char array where the result of the function can be stored. I do understand how String Arrays work. But I want to write 01:02 so it should always be 2 digits. I have tried to do this in so many ways but keep failing. You need to use heap allocation like malloc for the string in your function in order for the pointer you return to have any meaning. char* password_char() { int str_len = str_password. You can also have multiple buffers if needed. As a part of my project, I need to do segmentation on a time series. In python that would be: def func(): return "ninja" print (func) Now what I have in my Arduino code is the following: void loop() { Serial. String the_text = "Hello" void setup(){ the_text. h> // uses Ardunio pins: 11 - MOSI, 12 - MISO, 13 - CLK, 4 - CS (Chip Select user Jan 7, 2020 · Why are pointers used for C-strings? I don't know exactly, but C++ evolved from C, and C didn't have references. I have the array set up but am unsure how to check all the values in the array. loop() and setup() are just functions. malloc Syntax: #include <stdlib. Format string here is "Custom" with no format specifiers. There are three String arrays that contain words and they are printed to an LCD in a standard template. Now, I am told that I am playing with fire using Strings, so I try to understand how char[] works. it, Amazon. There are also alot of character array manipulation functions available, string is not a real good choice. e. I have been working on this simple problem for several hours over 2 days! I have seen a hundred different explanations (and tried ALL of them) and suggestions. Also, their Feb 10, 2021 · However, I cannot get it to work with a char array. begin(9600); String myString = "99,500,,45,W,5 Feb 2, 2024 · The function allocates memory using malloc and populates the array elements accordingly to return an array from a function in Arduino using dynamic memory allocation. println("setup()"); char* back = stuff(); Serial. They'd all have the same return type (String) and the same arguments (Void) and the same capture (&). A less common way is to return a pointer to the array FROM the function. Jun 11, 2022 · the name of an array is a pointer to the first element therefore arrays are passed by reference (changes made to the array in a function change the array in the calling function, e. Instead you can return a bool to confirm that the function succeeded. This way you will not depend on a global buffer. At this point I want to make function which is return integer if addr is a integer addr OR it will return string if addr is String addr. se Jan 13, 2023 · Hi, I read somewhere that some standard C functions do not work as well in the Arduino interface so I decided to see if it was still possible to return an array from a function. Jan 21, 2020 · So, the convention is to create a resource in your case the array in the calling function and provide the address to the called function. length()+1; //The +1 is for the 0x00h Nov 8, 2024 · The Arduino programming language Reference, Terminate a function and return a value from a function to the calling function, if desired. For example I have a String s = "Hello World", I want a function where I can pass the string and returns an array of HEX equivalent as such, array = {0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x20, 0x57, 0x6F, 0x72, 0x6C, 0x64}. I need the fuction to return the array so that I can further use it for feature extraction. NOTES: I need the String only, to use """Serial. Then I want the void loop to print whatever value it returns. Every C++ Jan 19, 2017 · So my array is defined as: char names[8][15]; That's eight names with each one have a maximum length of 14 + null. Nov 12, 2021 · Check they are of sufficient size though - you need to consult the function documentation for that. I am trying to move this to a Class so I can have multiple types of strings to capture, with different start characters or different end characters, or different delimiter characters, but one set of methods to Mar 31, 2020 · Hi all, I have CRC32 function that returns a decimal number (I do not want to change it, it works right), What I need to do next is to convert a decimal number into a String (yes with big S, :o not string, why? I have to) that will hold the HEX representation of the number. But IMHO concatenating two strings for output is a bad idea. co. Jun 24, 2014 · I would rather advise to pass the String by reference, to avoid additional code to be executed for nothing (copy-constructor, destructor): void sendSMS(String& thisIsAString) or even better, a const reference, if the string argument is not to be modified by the function: void sendSMS(const String& thisIsAString) – Apr 14, 2020 · String library you see in Arduino is not part of C++, it gives Arduino some features such as python-like or Java-like concatenation like String myString = "This string " + this_var + " another string";, which use dynamic memory allocation malloc at heap memory. It also couldn't pass arrays to functions, C-arrays automatically decay to pointers when passed as an argument. The substring. println in the main, the message is corrupted, I Apr 28, 2014 · I am trying to compare a a received string in arduino to strings in a textfile to find a match, the text file contents are read perfectly just that the function will not accept the variable string. A function to compare a sensor input to a threshold Feb 15, 2021 · Hello, I need help. char buf[11]; String … Jul 23, 2014 · If the strings have the same char on a single spot you could hash the strings to see if you get a unique value. pl and Amazon. Feb 16, 2016 · But I just can't seem to get it to work. I thought that would be simple, but I just can't figure it out. In setup: strcpy (cSSID, get_config_value ( SSIDFilename ); Function: char * get_config_value ( ConfigFilename ) char ConfigValue; // Open file and get config data Feb 10, 2021 · However, I cannot get it to work with a char array. println(MyString); compiles well, and I guess ( comparing sketch size and mem_check() results ), that both texts really reside in flash Arduino: function returning String-ArrayHelpful? Please support me on Patreon: https://www. The code below does that: it receives a pointer to an array of C-strings. No, it doesn't. So I wrote the following program using String Arrays. myString: a variable of type String; from: the index to start the substring at; to (optional): the index to end the substring before; Returns. when term = 2 it will return a string 500. The second type of string used in Arduino programming is the String object. Both the UNO and the ESP8266 were functional. A string object is used to initialize a text value. The following example is will make clear all your doubts. That single value need not be a simple type. my current solution is so slow it takes 4 seconds to load the list so I'm looking for an alternative. First of all, you cannot do an assignment like Apr 7, 2019 · strcat does NOT return "a new pointer". Happy to provide code if necessary but I think I am just missing a syntax trick. function_name: Name given to the function Feb 4, 2012 · sizeof(my_array) = not the number of values the array stores, but the complete size of the array in memory. Example 1: struct struct ab { long a; long b; } struct ab Conv(double num) { struct ab ab_instance; ab_instance. That means, if the function is called before the next measurement time, the function will not return anything. 0 Now I have some other strings declared like prog_char MyString[] PROGMEM = "This should be in flash as well"; Serial. 6. Use it to find your "from" value and the following "," from that point. Have text() return void and call it like this: text(2); Mar 30, 2011 · May be I have understood my problem. Normally the compiler gives you at least a warning about that (maybe you have to turn the warnings on in the settings of the Arduino IDE). The below uses the String functions. Considering how complex arrays of functions are to declare, I'd imagine these aren't easy either! Thanks! Jul 27, 2016 · Sure you could. Try to learn how to use character arrays instead and you will avoid running into memory issues. return; Sep 12, 2011 · Just as a reference, below is an example of how to convert between String and char[] with a dynamic length - // Define String str = "This is my string"; // Length (with one extra character for the null terminator) int str_len = str. The thing you have to watch out for here is if the array is local to the function. etc. Nov 3, 2010 · A string array in C can be used either with char** or with char*[]. If you can use std::string rather than String then it would be even better. But when I googled for info on [arduino "array of strings"], I was astonished to find each reference taking me instead to examples of character arrays being loaded with Jan 28, 2024 · This variable numberAsChar is deleted as soon as the function returns. String Tutorials Apr 13, 2017 · Hi! I'm rather new to lambdas, and I was wondering how I could make an array of them. Very simply Jan 16, 2024 · Here is the anatomy of a return statement inside an Arduino function: return_type function_name(parameters) { // Function body return value; // Return statement } Breaking this down piece-by-piece: return_type: Data type of return value (int, float, bool, etc. But, if you follow my advice, you will get more compile errors. I'm not clear on how Char Arrays work. The function 'readEEPROM()' returns a single char. Output Feb 16, 2021 · Now you have the second problem: When defining a variable inside the function, it will become invalid, when you exit the function. length() + 1; // convert string to chat char char_password[str_len]; str_password. read(0) != 0) { for (int i = 0; i < 32; ++i) { rw_ssid += char(EEPROM. I have some default text (easy enough), but I will like to limit input to 8 character strings. Jun 28, 2012 · This code wont do if the incoming strings are of variable length though. However it uses the STL, and my recent attempts to get that working in 1. A function can return a single value. String result[NUMBER_OF_SENSORS]; should be correct. For example, I would make the following definition: int one[5]={2,3,4,5,6}; // 5-number array to pass along Then inside my loop I would pass this to the function 'myLED()' which I hdefine later: void loop() { myLED(one); // pass along the 5 numbers to the function Jun 13, 2012 · it returns first string stored in string array c. Functions of the string manipulation library often use this method. In setup: strcpy (cSSID, get_config_value ( SSIDFilename ); Function: char * get_config_value ( ConfigFilename ) char ConfigValue; // Open file and get config data Sep 24, 2019 · Hi all I am using an Arduino Function that returns a String object. ``` #include <SPI. Here is the standard syntax for a return function in Arduino: dataType functionName(parameters) { // Function code return returnValue; } Nov 17, 2013 · Many of the standard C string functions work like that - you pass pointers to character arrays, and often a length (though with strings it can compute the length a lot of the time) and the arrays are modified by the function. Currently, I read each file as a String and Apr 16, 2019 · I'm not sure where to post this but it seems like a programming question to me. But the user of your function needs to know that if they call the function a second time the data will be overwritten. On the other hand, they don't need to. Aug 7, 2010 · I want to pass an array as a parameter of a function, then have that function change the values in the array, and have those values be available to use from the original function. A string is a NULL terminated array of chars. Then it allocates the array first (sizeof(char *) * count) elements, then it allocates each string in this array and assigns a value. I use this utility Array container: Arduino Helpers: Array< T, N > Struct Template Reference It's a wrapper around standard C-style arrays with some added features, for example, you can slice it, and you can return it from functions, which is not something you can do with normal arrays. It implements some functions that replicate functionality provided by the string functions that are available on the Arduino. I use a custom "getWord" function, but similar can be done with strtok(). So if an array had 6 sentences, I would want the function to return a 6, but if it has 4 it would return a 4. For example, the function header for function modifyArray might Nov 10, 2023 · Hmm, not entirely sure how you've structured your code as I can't see the entrer_code() and your entire logic with the Serial. You could however pass the array to build_array as an argument, as well as its size, and fill that instead. Define input as String. I send a String ("1,34,300,293,2") from an html site via MQTT to my Arduino. Aug 12, 2017 · So I noticed that if the result returned is NULL, and I don't do additional checking for it first, it will crash. Here's an example of what I'm trying to do. So, they would need to strcpy (that is, copy) the data before it is overwritten. But, since C++ templates are butt-ugly (IMO), I’d just cast the array name as a double * and pass it to the function along with the number of rows and columns. For example, something like this: int TestArray=0; int BuildArray() {int MyArray[10]={0,1,2,3,4,5,6,7,8,9}; return MyArray;} void setup() { Serial. Here is an example of what I am talking about: void loop() { byte data[2] = getdat(); } byte getdat() { byte dat[2]; dat[0] = 'a'; dat[1] = 'b'; return dat; } I have tried some variations of declaring the array and get Jan 11, 2015 · arduino, function to return char array. How would i go about doing that? Oh and how can i get the length of an array? Would be correct if your function was correct. Feb 25, 2020 · Hi. But if I return an empty string instead, the strcmp function won't crash. the first attempt i tried converting the String Object into an std::string type then used Apr 2, 2020 · Some compilers optimize that for short strings, some dont so its up to you. But the bigger problem is that you are initializing the result array to a single element. For example: arrays; string; arduino; or ask your own question. So the natural way to pass an array of characters to a function was to use a pointer (char *). patreon. You pretty much can't return an array, neither a pointer to a local array. Return the number of entries in the array you used. String ary[] = {ss}; and thes lengths of arrays can't be changed after initialization. However, you cannot return values stored on the stack, as in your function. Heap fracture is not a big deal if you have a Gb of memory and cleaning functions as OS, but for Arduino its large chunk of memory that is now corrupted. First study char arrays, will make things more straight forward. length() + 1; // Prepare the character array (the buffer) char char_array[str_len]; // Copy it over str. toCharArray(char May 26, 2019 · The OP wanted a conversion from 'String', we know it's possible issues, (being possible fragmentation of dynamic memory over time) But that was the request, i don't know if it is a result of an external function, if so then using c-string it would need to be converted into that first for any of the c-string code to work. But it doesn't seem to be working, the 'encoded' char* seems empty. there I have a for loop to turn on leds int the int Array. The problem is that if I call the function after the Serial. Here is an example F8nxtH - Online C++ Compiler & Debugging Tool - Ideone. Sep 14, 2016 · Hello people, I'm new here but I already had a look how to implement this. is that possible to make two kind of return type for a method. Feb 13, 2011 · Peoples, I'm making a call to a function that creates an array of char and populates it. I want whole string array to be returned. an array of char pointers: char* myArray[length]; myArray[0] = "text"; return myArray; Your function will need to have a return type of "String * " or "char ** " respectively. com/roelvandepaarWith thanks & pr Feb 6, 2013 · Hi there, I'm interfacing a LCD with a consumer, prompting to enter some text via serial. toUpperCase(); } void loop(){ for Apr 6, 2016 · C++ has a class called String (note the capital 'S') while C prefers to use a char array for strings (lowercase 's'). com, Amazon. If you have an integer-array, you can take the complete array-memory-space which is reserved for the array and divide it by the size of an integer-values. If you made cti into a properly terminated string, an array of characters with a '\0' in the last index, you could use strchr(). What I want to do is simple but there is something that I do wrong. Jun 15, 2019 · Inside of it is the only return statement. An object is a construct that contains both data and function. That is the way that most string. I'd like to to some things like: char string0[10]; char string1[10]; char string2[10]; char string3[10]; char string4[10]; //somehow make an array or something of those str…. return; return value; Parameters. Any idea? Jun 6, 2022 · Ubuntu Arduino IDE ESP32 Simple, simple, simple All I want to do is return a String (big S) from a function. The contents of that memory are undefined once it has been released and its data may or may not be valid. I KNOW this is simple, but I'm just not getting it! I did have this working: Aug 16, 2010 · The combine function above purports to return a char, but in fact the return long_s is returning a char* as the comment after this line suspects. Will the arrays you pass to the function always be 5 elements in size? At present, your function is "hard coded" for this. From C language, I know that it is possible to return an array by declaring a variable as static or using malloc. Jun 22, 2015 · My project needed an "Array of Strings" to simplify the code, allowing me to manipulate several strings at once using "for" loops, instead of having to type a separate line for each string I want to read, write, or edit. Here is the simplest program that demonstrates the problem. I do something similar in my CLI library. But, it can not be an array. The number returned by parseFloat() has 24 significant digits. I need to concatenate the two strings together because the message is going out to Twitter. myString. Returning a dynamically allocated array of strings is never the correct thing to do in C++ (unless you have a proven specific case). I just want to call the build_array() function and return the array of strings. Well well now I know. readString() for the ID code part. Syntax. See also. uk, Amazon. read. Arduino String Character Arrays. I've tried to simplify the program, but couldn't figure out the cause. e. 0. Any C book will have a whole chapter on strings, or I'd leave it on the May 14, 2024 · If the ending index is omitted, the substring continues to the end of the String. The following code works: void setup() { // put your setup code here, to run once: Serial. a = floor(num); ab_instance. I come from a python background so forgive me if I am missing some essentials here. Also your code was missing Jun 16, 2012 · I found in Arduino Playground - Memory Serial. Here is the code : Jan 15, 2015 · At the moment, your function is expecting one string: void myFunction(String items) Try changing it to an array: void myFunction(String items[5]) You will also need to fix some problems with your serial printing . but I couldtn figure out how to convert the string to my int array. The function returns a pointer to the newly created array. I need to use an arduino mega for testing the system. Even if you declare the array in the sub as a Variant and the function returns an Integer array that will not work either. h functions work btw. The key processing and display is handled in a function. Mar 23, 2015 · The function which guix wrote for you belongs OUTSIDE any other function. The problem is the functions to get the time and date return an int. For a function to receive an array through a function call, the function’s parameter list must specify that the function expects to receive an array. As my script runs, the user enters his/her name via buttons and an LCD. When I used: C++, function to return array as string. The value Dir is deeded to determine direction of the LEDs The sketch runs great, but when you un comment line 75 and comment out the lines below it, the sketch Aug 27, 2015 · I want to create a structure called CarSpeed it has 4 int FR,FL,BR,BL (FrontRight,. But I want to expand the interpreter and allow the user to get an array of data or other structure in response to their query. The return value from the function is often either one of the pointers that is passed (why, I don't know) or something Arduino String Object. print("rPASSWORD: "); Jun 1, 2014 · Hello I have a question of how can I write a function that returns a string? I have an arduino mega with an lcd connected an want to write a time and date on it. read(i)); Serial. Does anyone know how to do this? Please let me know if this is not clear and thanks for your help. Then other functions, or code in loop, can access the array also. FYI: debug() and debugLn() Aug 5, 2015 · I wrote an expression parser a while back that does what you ask. The string and the array address to put the data in. One of the things I want to do is have running averages set up for each reading so I can see the average for the last minute/hour/day. I am trying to get it where I have a function for each letter and depending on the string, it calls the functions in order for each letter. , Substring, IndexOf, etc. Unfortunately I ran into the "cannot convert float* to float" problem, and I'm not too good with pointers. I tried simply sending the String object, in the hope that some implicit conversion will happen, but none did. When the pointer is received by the calling function, the data has been junked and no longer contains the expected characters. The function that returns an array has to be of EXACTLY same type. I included in the following code 2 functions: the first one returns the length of a specific array and works correctly, the second one should return the length of the array that is passed as parameter. begin(115200); Serial. Ask Question Asked 10 years, The strcpy_P function copies a string from program space to a string in RAM ("buffer"). After using for ESP, the translation does not report any error, but the conversion does not work. I tried to use sizeof but it doesn't really work. String = "This is some text"; Instead, use: the parseFloat() function returns decimal numbers. Apr 30, 2018 · I am trying to write a function that takes just two parameters (A string and a delimiter) The function splits the string at the delimiter(s) and returns an array with the substrings as the values. That class performs dynamic memory allocation to create space to hold characters. read(i)); for (int i = 32; i < 96; ++i) { rw_pswd += char(EEPROM. de, Amazon. This is my code without the MQTT part Could you help me pls? Best Marvin 🙂 #include <Adafruit_NeoPixel. Suppose that get data just puts a string "ABC" in the result array it would look like. However Apr 5, 2022 · I am following along with this tutorial here. b = num * pow(10,6) - a * pow(10,6); return ab_instance; } Dec 29, 2020 · Don't use String class. On the page for printf it says of the format string: C string that contains the text to be written to stdout. Nov 18, 2014 · The variable data, passed to the function process_data(), is declared as a pointer to char, which will be used to iterate an array of chars. I know that Strings take up a lot of storage so I was looking for a workaround. How do I declare an array of strings in Arduino? To declare an array of strings in Arduino, you can use the `String` data type followed by square brackets and the number of elements in the array. 4 have failed. I am trying to extract a subString from a main string in a function. May 25, 2019 · Unless the array is a c-string (null-terminated char array), you will probably need to also pass its size into the function. pmigyik xeazu jsnvfvz csvyrn ksu gxjxeq wyq rpeqphl vdwhpx yipc