Questions tagged [string]

A sequence of characters -- including letters, numbers and symbols -- often used for representing information in a human-readable format.

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1answer
94 views

String Split Issue

I am getting multiple messages from a GPS device at different frequencies. After getting strings I have to save this data on the SD card. It works well when we have the same frequencies messages but ...
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1answer
33 views

What's is the best way to convert std::string to String?

Pardon me, I am a novice programmer. I was trying to use the toInt() function for a std::string but I noticed that toInt() only works for the String class. So, I have an std::string sliderValue and ...
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2answers
27k views

How to convert String to byte array

I have the code, it's purpose is to receive the string from a comport like: Set@1234567890123456@1234567890123456@1234567890123456@1234567890123456 and translate it into four byte arrays byte user1[16]...
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1answer
32 views

Join Serial Data Seperated by Newlines?

I have two Arduinos connected through Bluetooth. One sends a string of data similar to 506:507:1\r\n. The data can vary similar to 0:1000:0\r\n. I already have functions to break that string down into ...
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4answers
1k views

String to float on Arduino

I'm trying to convert a String to a float but I'm running into issues with precision, even with the Arduino's own String example I'm getting bad results. Example 0: Input string: 1.234567 After ...
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1answer
53 views

.toFloat() giving incorrect anwsers

I am broadcasting a fixed value float over a HC-12 radio which is then received by another HC-12 radio. I am then trying to convert that String to a Float which requires 6 decimal places. However, ...
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1answer
70 views

How to assign a string-variable to a StackString based on the StackString-library?

I'm trying to use the StackString-library which offers not to eat up RAM over time by re-assigning values to strings. I started from scratch and wrote a very basic democode which works. Then I added ...
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2answers
638 views

Reading from SPIFFS - What's the best way to deal with a string (or char) array with undefined length?

I've read that it's best to avoid using String in Arduino so I'm ready to use a char array if it's better. I'm reading the file names from an SD Card and my goal is to store them in an array and then ...
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1answer
1k views

Convert JSON into string for MQTT

I am trying to publish json object into string with following snippet JSONVar data; data["chipid"] = chipId; data["co2_equivalent"] = co2_equivalent.c_str(); data["tvoc"] = tvoc.c_str(); data["...
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1answer
60 views

Arduino keypad variables to serial port

I've been trying, for over a week now, to create a program that will store my keypad presses into variable, and with a press of an enter, it will switch to the next variable to store the presses. The ...
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2answers
77 views

İs that possible to a function return String OR Int depends on address

Well, I'm trying to use a HMI display and this HMI storing datas in separeta addreses. Such as integers addr. is between 0x80000 to 0x9ffff and also for string's addr is between 0 to 0x1ffff. At this ...
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2answers
5k views

Using StringStream in Arduino sketch

I learned about StringStream today at work. #include <iostream> #include <sstream> #include <stdio.h> #include <string.h> using namespace std; char* getSql() { float ...
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1answer
265 views

How to convert a String to Hex array

I am trying use a HMI display. If I want to send a data, for example I want to write "TOPWAY" to 0x00000080 address it should like that: Serial.write(0xaa); // packet head Serial....
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1answer
96 views

Using index of to search for multiple characters

In my Arduino project, a string will be received. I understand using .indexof to find the placement of a certain character in the string. My problem is that I need to find the first occurrence of any ...
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3answers
15k views

How to clear of contents of string in Arduino?

Currently I convert the characters in char received[20] to string using String randomString(received) and I am able to display it using Serial.println(randomString). After displaying the string, I ...
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1answer
66 views

Find OK or ERROR in serial string

I am trying to figure out how to capture the OK or the ERROR from a SIM800l. I have tried mySerial.println("AT"); while (mySerial.available() > 0 ) { String str = mySerial.readString(); ...
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3answers
21k views

DateTime to string

For some reason I can't use the Time.h lib. Can you guys tell me how to create a string from the datetime into a format like this: yyyy.MM.dd:hh.mm.ss 2014.10.29:07.12.33 Seems odd that I can't ...
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6answers
3k views

Using String instead of C string, yet another attempt to touch a loaded issue

I've been reading a lot over the years why we should not use the notorious String class and how heap fragmentation is bad practice and not professional and we should never use it in our programs or we'...
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1answer
301 views

invalid conversion from 'char' to 'const char*' [-fpermissive] on a string

I am compiling some code I didn't write, and it bombs out with the error message invalid conversion from 'char' to 'const char*' [-fpermissive] on the line if (loginPassword == '\0') loginPassword = &...
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1answer
106 views

How to properly handle the Arduino String

I've read that the Arduino String is bad as it causes memory fragmentation, so I try to avoid them mostly. But I still have some occurences where I'm not quite sure if they are ok after all. The first ...
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5answers
8k views

How to compare a string

How to compare a string coming from serial monitor with some predefined text stored as a local variable? If I say: int led = 2; String a = " abcds"; void setup(){ Serial.begin(9600); } void loop(...
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3answers
2k views

eval() function for Arduino?

I plan to do the following: void setup(){ String term = "12 + (2 * 5)"; int result = eval(term); // eval function (from Python) Serial.println(result); // expecting 22 } However there is no ...
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3answers
1k views

How to fix memory-leak code in ESP8266/NodeMCU caused by string concenation?

I have following code in loop() in NodeMCU. This part is before setup(): String serial_data_read = ""; // for incoming serial string data String serial_data = ""; // for incoming serial string ...
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1answer
107 views

Arduino Serial.readString() trouble

Hello everyone I write my code and have some troubles. When I write on in my serial monitor my buzzer condition wasn't changed. Can you help me realize the reason. I wrote code with int type and it ...
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1answer
62 views

Substring: What is causing my output to be truncated?

I suspect that I might be using too many resources, because of the strings, but I am new to Arduino, so not sure where I am going wrong. Any help would be appreciated. What it should do when complete:...
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2answers
49 views

Get a specific item from comma separated text

I use bluetooth (works like serial monitor). Let me say i send a text to my hc-05 (same as sending to serial monitor) My current code is displaying text from serial monitor/HC-05 TO LCD #include <...
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2answers
1k views

Clearing string buffer with memset after a serial read

In using the SerialTransfer.h / pySerialTransfer libraries to send commands between my laptop and an Arduino Mega, I am sending multiple sequential strings between the devices. However, I'm having ...
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1answer
647 views

Arduino - Extracting Multiple Strings from Serial Read

I am trying to write an Arduino code that reads a long string, example <11,22,33>, through the Serial Monitor and then stores the 11,22, and 33 into separate bins of a matrix array. So the user ...
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1answer
71 views

Remove unwanted characters from char type

I'm working on an ESP8266 module that needs to fetch date data from worldtimeapi, everything works fine but the problem is How do I strip of the time field off the datetime JSON response without loop. ...
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0answers
31 views

Can't test for equality with string received from bluetooth module

I am trying to keep the program within a loop until the user inputs "ok" on the Bluefruit Connect App. I use the readString() function on the bluetooth object (ble) to read from it. Before ...
51
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13answers
251k views

How do I print multiple variables in a string?

Say I have some variables that I want to print out to the terminal, what's the easiest way to print them in a string? Currently I do something like this: Serial.print("Var 1:");Serial.println(var1); ...
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2answers
447 views

How to read incoming HEX values from Serial.read() method?

Brief description about the problem History Communicating with a old VersaStat II used GPIB port but the GPIB ports PCI card stopped working but there was a another port 25 pin rs232 Serial ...
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2answers
68 views

Arduino - Function -> return Cstr instead of string

I have following function for my Arduino: String readLine() { String received = ""; char ch; while (myFile.available()) { ch = myFile.read(); if (ch == '\n' or ch == '\r') { ...
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2answers
111 views

Firmata.SendString doesn't work with specific `char` variables

I have a Firmata sketch, that accepts string messages, partitions them and sends its' parts back to a Firmata client program. My problem is certainly at the sketch's side. The problem is that Firmata....
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1answer
219 views

Error initializer-string for array of chars is too long using ESP32 Webserver

i tried to use an asynchronic webserver for a new project with friends using this tutorial. We want to run an FFT while also changing some settings via the webserver. Since the tutorial only put code ...
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1answer
75 views

Any explanation for this behavior?

For the below code snippet const char* fr_fbdb(char tag[30]) // fn for retrieving data { char full_path[120]; const char *_dt ; strcpy(full_path , base_path); strcat(full_path , tag); ...
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1answer
119 views

String comparison problem

I have this callback function in my Firmata sketch. It receives a string as a character array and does something with it. The problem is, that the string is being sent to the Arduino in T\0h\0i\0s\0 ...
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0answers
49 views

Erratic behavior in String based functions

I've been working on a cipher based project, and I wanted to prep the encrypted string for use with the RF24 library. Since the payload size for the RF24 module is 32 bytes, I wanted to stick with ...
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1answer
758 views

What is the purpose of F() and FPSTR() in ESP8266WebServer -> FSBrowser?

I found this code sample from the FSBrowser (Flash File System) example in the ESP8266WebServer library: replyServerError(FPSTR(FS_INIT_ERROR)); replyBadRequest(F("DIR ARG MISSING")); I was ...
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1answer
187 views

Reading a string from Firebase and storing it as a CString

I have a mobile app (done using MIT App Inventor) storing some values to a Firebase database. App inventor stores all the values as strings (i.e. with quotes, and strings have quotes enclosed within ...
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1answer
81 views

Why are characters with value above 127 "padded" with 1s to be 16 bits long, while ones with values 0-127 aren't?

I am using the Arduino IDE to run and monitor, with an Arduino Nano clone. This code shows what I mean by the question: char foo = 127; char bar = 128; Serial.println(String(foo, BIN)); Serial.println(...
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0answers
174 views

incompatible types in assignment of 'const String' to 'char [32] using server.arg

I am trying to create a class and getting getting the error incompatible types in assignment of 'const String' to 'char [32] when I declare char inString[32]; and try to set it as inString = server....
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2answers
84 views

Is there a limitation of how many instances of the `String` class?

Platform Attiny85 with AttinyCores 1306 OLED i2c with Tiny4KDisplay Goal using a joystick for menu navigation up/down choose left enter (not finished yet) right back (not finished yet) inverse ...
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2answers
284 views

strcmp doesn't seem to work

I'm trying to compare a char array that I'm assembling to a string and I'm having trouble comparing the strings. I'm getting the data for the char array as a set of bytes and I'm compiling it into a ...
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3answers
88 views

Properly escaping very large strings

On an esp8266 I want to create a little webserver that shows me a dashboard with charts and stuff. For this I wanna include the echarts-library as it works offline. To access it the only way I can see ...
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1answer
297 views

Why use \" in arduino code?

While working with JSON parsing I noticed that the char type data string is written like this: char json[] = "{\"sensor\":\"gps\",\"time\":1351824120,\"data\&...
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1answer
181 views

Converting c string to integer to unsigned char

I'm Trying to grapple with types between two different libraries. The gist is that I'm using the ArduinoWebsockets library to receive information coming from my api that I then want to render out to ...
2
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1answer
282 views

Comparing a String after reading it from Serial fails

I have bought an Arduino starter kit online, everything seem to work but when I try for example to use ifs (and other conditional statements), the LEDs do not turn on. Here is a code for a little ...
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1answer
218 views

Converting 8 bit binary to a hexadecimal pair as unsigned char

I have a function: void Epd::SendData(unsigned char data) { digitalWrite(dc_pin, HIGH); SpiTransfer(data); } At the moment I am hardcoding data sent to it by calculating on paper and then writing ...
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2answers
726 views

Read Comma Separated String

I have a string that looks like this "10.00,20.00,-50.00," in which these are angle values and they have 2 decimals and can be negative. I want to separate them into 3 separate floats. Here ...

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