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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28 views

First sprintf-call works, second (identical) does not

In my current project I'm using an Arduino Nano, an RTC-Module, SD-Module and an OLED-Display to log time-values. I'm currently trying to implement following function: char *onString = (char*)...
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2answers
19 views

How to Sort a String with Number by Ascending

I have trouble figuring out how to sort a String that has a Number in it. The String im sending looks like 112:AAAA and 111:EEEE, how would I sort it so that the 111 will be the first in an array but ...
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86 views

How to decrease delay for String concatenation + Arduino Due

In my project I need to add a delimiter between integer numbers. In the following code. I add a "," between integer numbers obtained from inputsig matrix. The problem is that concatenation of these ...
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33 views

Have ESP8266 read 'text/event-stream` from flask in single request

I have a route in Flask which serves an event-stream: @app.route('/input/<string:blah>') def index(blah): def generate_random_data(): while True: r = random.random() * ...
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1answer
38 views

char buffer to String in Arduino UNO

String getAPIData() { char res_buffer[450]; int numdata = inet.httpGET("myserver.com", 80, "/call.php?id=1&q=1&code=1001", res_buffer, 450); String result = String(res_buffer); Serial....
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1answer
21 views

Second item in array not gets assigned from struct object, ArduinoJson

I got the below code generated this amazing tool. const size_t capacity = JSON_ARRAY_SIZE(2) + JSON_OBJECT_SIZE(1) + JSON_OBJECT_SIZE(4) + 2*JSON_OBJECT_SIZE(7); DynamicJsonDocument doc(capacity); ...
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2answers
97 views

Convert String to IPAddress

How can i convert a String to IPAddress on arduino / esp ? etc. "192.168.1.2" -> IPAddress(192, 168, 1, 2) Tried this void setup() { Serial.begin(115200); IPAddress apip; const char *...
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1answer
28 views

arduino mega multi integer values reading on other arduino mega

I need two Arduino communications. The master arduino from the slave arduino needs to read 16 signals. The sample serial port output from the slave is as follows. @ 125 @ 13 @ 874 @ 1023 & 950 @...
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2answers
113 views

How to actually concatenate two Strings?

I'm using the SPISlave library, and I have the following code snippet: String arg; SPISlave.onData([arg](uint8_t *data, size_t len) { data[len] = 0; arg += String((char *)data); // ... } The ...
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2answers
83 views

How do I implement reverse enumeration?

Basically I'm trying to output a string based upon a value in an array, the following code is what I have come up with to achieve my desired result, but I have a feeling that there is a better way to ...
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29 views

How to create parametric variable in class decleration

I hope the subject of this question if correct. in timeOUT constructor, 3 more instances of other class are defined: endTimeOUT_inFlash(key1), inCodeTimeOUT_inFlash(key2), updatedTimeOUT_inFlash(...
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1answer
29 views

Update `char* `

I have a class containing few char* variables: char* msgTopic = "myHome/MSGS"; char* groupTopic = "myHome/All"; char* errorTopic = "myHome/Err"; but, I wish to have it defined outside the ...
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1answer
54 views

From Strings to int problem

I create applications for a computer that is to be used to control the robot arm. I wanted to make the first attempt to run the application not on the motor, but on the diode and check if it will ...
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2answers
39 views

Parsing Arduino Receiving Strings

I'm currently using google geolocation to get location data to one nodemcu and sending it through serial to another Arduino. The serial command I'm getting right now is, 1.450187T103.824745 I'm ...
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1answer
54 views

How to stringtok this long string? [closed]

I have a string, "id,port,password,ssid,delay,flag,class,category" Please tell me how can stringtok this and find out the "flag" value(0 or 1)? Here is what I tried: void setup() { char input[]...
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1answer
53 views

Change data-type String

I'm currently working with an ESP8266 NodeMCU V3 and an IR transmitter breakout board. The module receives NEC IR commands trough a HTTP request and then sends them trough the IR transmitter. Getting ...
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33 views

BLE splitting string data

I am working with BLE 4.2 (ESP32) that sends IMU (accel, gyro, mag) data to my mobile app (Android). Unfortunately, I can send only 20 bytes in one packet. This is the code I have: (I am connecting ...
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39 views

Sensor to detect whether string is in tension?

I need a sensor to detect whether there is tension on a string or not. I do not need an accurate measurement of the amount of tension- just whether the string is being pulled on or is taut. ...
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2answers
80 views

Compute SHA256 of string and output to string

In my Arduino project I want to compute the SHA256 hash of a string and store the result to a string, and do this recursively many times (i.e. compute hash of hash of hash etc...). So my goal is to ...
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110 views

string.charAt() is not returning the correct value

I know this is a super basic question, and I did try debugging, but somehow I think I am missing the way variable stores value in Arduino. int enablePin = 2; // ebanble pin for slave String ...
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1answer
279 views

How to compose an HTTP GET request URL with key/value parameters

I am experimenting with some code running on an ESP8266 board to retrieve data using a web API. I would like to store the host address and key/value parameters (API key etc.) of the GET request as ...
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1answer
98 views

Send Strings via SPI both ways using two Arduino UNOs(Master to Slave & Slave to Master)

I need to create a two way String exchanger via SPI with two Arduino UNOs. Strings and their lengths are independent variables of the main loop and they can change with every iteration. I need both of ...
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81 views

Compare barcode scanner string with existed string

I have a project which is reading barcode scanner result then compare with an existed string. I have used the library USB host shield in order to read data from barcode scanner then I would like to ...
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1answer
84 views

ESP8266 crashes when trying to copy a string into a big char

I'm trying to parse with tinyxml2 a modest XML (3.4kb) to retrieve some data. My ESP8266 crashes every time I try to use the toCharArray method. here's my code // here I'm getting an http request ...
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1answer
59 views

Problem with String& argument of a function

I am trying to send SMSs using a GSM module with Arduino Mega. I have followed a tutorial and downloaded the SIM908IDE100 library. I am using the function SendSMS(String&, const char [27]);. It ...
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4answers
222 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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1answer
134 views

Mqtt not subscribe on topic that's converted from String to char array

I am still not sure what should be the exact Title for this question, because I don't know where the problem is. I am using #include <MQTTClient.h> mqtt library to subscribe on a topic. This ...
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0answers
449 views

String.format(“%i”,i) equivalent

How do I format an arduino String when I do not want to print it? I know that one can use printf() or other methods to print a formated string and unfortunately that's all I find with google. But that'...
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32 views

Problem: char string not working with SoftwareSerial.h

I am creating a program to display text on an OLED display and then have it sent to a thermal printer. The issue is my second char string: word_buffer When I try to use word_buffer for any reason it ...
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1answer
84 views

Parsing Data and Comparing two string in arduino

I am working on my final assignment. The problem is I want to make a prototype tool, with 2 string compare. If I send data "OK DISC DISCLOSED: 341513DB689AOK RSSI: -056 OK NAME: CarBT1 OK DISCE" will ...
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2answers
44 views

String Comparison Result [closed]

I've following code: char a[5] = "bang"; char b[5] = ""; void setup() { // put your setup code here, to run once: Serial.begin(9600); } void loop() { // put your main code here, to run ...
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1answer
229 views

Weird behavior with char/uint8 arrays

So I'm trying to read an 8-byte character string from an I2C device and print it to the serial console. This raw 8-char array is not terminated when it comes from the device, so I'm pretty sure I need ...
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1answer
96 views

How to parse multi line serial data with an unknown number of lines? [closed]

Here's the example data I've read in H-Term: \r\n \r\n NO:0015\r\n G: 5.97kg\r\n T: 0.00kg\r\n N: 5.97kg\r\n \r\n \r\n How to save the number including "kg" to each variable (NO, G,...
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1answer
119 views

Large(ish) strings failing to send over WiFi101 using WiFiServer

I've based a sketch off the vanilla WiFi101 server examples. If I define a const char array like this: const char HTML_index[] = "<html><head></head><body>test</body>&...
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1answer
936 views

Splitting a Serial.readString into string array

I am working on a project where I need to split incoming data from serial (time to be exact, so aa:bb:cc) and need to split it into aa then bb and cc, ideally into an array. I know I could use ...
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2answers
152 views

How to combine strings and text together?

I'm trying to combine two strings (strings/int) together with text in below code: int foo = String((char*)payload).indexOf(' '); int message1; int message2; message1 = String((char*)payload)....
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1answer
223 views

Attempting to read random string from SD card

I was wondering if anyone knew how to read in a random string from a file named "PhraseList.csv" or "PhraseList.xlsx" (whatever is easier)? There is a list of 10k. #include <SD.h> #include <...
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1answer
40 views

Assign and control Digital pin from String

Here is modified version of Blink example #define D8 13 String p = "D8"; // the setup function runs once when you press reset or power the board void setup() { // initialize digital pin ...
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109 views

append a String on ArduinoJson Object value

I've a json string request coming from server and I convert it into json object StaticJsonBuffer<500> jsonStaticBuffer; JsonObject& root = jsonStaticBuffer.parseObject(String(msg)); ...
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2answers
48 views

Command through Serial monitor does not properly work in Arduino

I am executing a function in Arduino by giving String input to the serial monitor. The issue here is when i enter "SHOW$" (without quotes) the function showData() works but when i enter the same "...
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79 views

How to store an array of doubles? As array of doubles, Strings or const char *? Then convert back to use?

This seems like an old, solved problem, but I can't find any simple answers. I'm reading latitude and longitude data as Strings from a file (about 50 points), but they are really double float numbers. ...
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1answer
47 views

Help to delimit and read specific contents of incoming HTTP string

I am sending strings to an Esp8266 via web browser. The below code returns the following in serial monitor if I send in browser: Send from browser to esp8266 - http://192.168.1.220/s1s2s3s4s5d1 ...
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2answers
330 views

String compare when using Serial

I try to detect commands given by user in Serial Monitor, but strcmp fails to flag as identical. What do I do wrong ? Is there a better way not reading as String and convert to char for comparison ? ...
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1answer
55 views

How to define and use a list/array of chars using `Serial.print` [closed]

I wish to define a list of months names and access it when printing a report. Array was defined as follows: const char months []= {'Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov',...
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1answer
423 views

Using c_str() on String for IPAddress with NTPClient provides wrong values

Libraries NTPClient Board Olimex ESP32-POE board Behaviour I have written a code that connects the board to a local NTP Server (which is an embedded board). I tried assigning the IP Address of ...
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2answers
2k views

Problems on convert byte[] to String

I'm reading a RFID Card from RC522 and send the data to my computer. My problem is the conversion of byte[] to String or std::string. #define SIZE_BUFFER 18 #define MAX_SIZE_BLOCK 16 byte ...
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3answers
267 views

Arduino IDE c++ 11 raw string literal have issues with // in http://, complier thinks // is comment

char webpage[] PROGMEM = R"=====( <html> <head> <script src="https://cdnjs.cloudflare.com/ajax/libs/svg.js/2.6.6/svg.min.js"></script> </head> <body> &...
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3answers
937 views

Why is 'n' parameter of snprintf ignored?

I have found that the n parameter of snprintf() seems to be ignored in my code. char asdf[10]; Serial1.println(snprintf(asdf, 2, "hello")); This prints 5 when I would expect it to print 2. What is ...
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2answers
110 views

ArduinoJSON: Using a reference to a reference when parsing array of arrays

I started to play around with the ArduinoJson library to parse data I got from one of my APIs (the format of the JSON data I get from my API can be improved for sure, but the software I had to ...
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3answers
2k views

formatting strings in Arduino for output

I wander what is the best option for formatting strings in Arduino for output. I mean what's a preferable way in the point of view of performance, memory usage – things like that. I see, people ...