Questions tagged [functions]

Segmenting code into functions allows a programmer to create modular pieces of code that perform a defined task and then return to the area of code from which the function was "called". The typical case for creating a function is when one needs to perform the same action multiple times in a program.

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Using functions in header files [closed]

I want to include a function in my sketch I moved to a .h file. I did it as follows: My code: #include "header.h" void setup() { fct(); } void loop() { } My header: #include "...
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Can you create an array for functions? [closed]

Let's say I want to create 10 functions, named Function1, Function2 until 10. Each function is used if a certain variable is equal to its number. Rather than using individual functions, I was ...
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This website in Arduino lists language references like functions and structures. What makes structures there different from functions?

https://www.arduino.cc/reference/en/ Language Reference Arduino programming language can be divided in three main parts: functions, values (variables and constants), and structure. functions For ...
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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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Doing several things at the same time with functions, objects or interrupts?

First of all, thank you for taking the time to read this. I am a newbie, so apologies (done examples on arduino website, basic C++). I'm trying to get an idea of what the best way to structure a ...
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29 views

Receiver sleep mode RDA5807M

Good afternoon guys! I have a radio receiver connected to an arduino and I want it not to work all the time, but to turn on by the arduino timer for a certain time, and the rest of the time the ...
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1answer
24 views

Error Compiling for board Arduino Nano while using Adafruit GFX

Whys is this happening to me?? I have to meet a deadline please help!! Here is my code. #include <SPI.h> #include <Wire.h> #include <Adafruit_GFX.h> #include <Adafruit_SSD1306.h&...
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1answer
105 views

What is touch_pad_get_status() supposed to return?

What I want to do: I have 7 touch buttons on my board (ESP32 TTGO T-Display) and I want to attach interrupts to everyone, calling the same function. In this function I would like to use ...
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92 views

How to use this confing function

For INA3221 current sensor, I found this library, however, I don't understand how to use the INA3221SetConfig() function as defined in the .cpp file link. void SDL_Arduino_INA3221::INA3221SetConfig(...
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2answers
134 views

Problem with a function having a parameter with a default value

I've got a problem using a default value for a function parameter. This code gives "'blink' was not declared in this scope": void loop(void) { blink(12, 2, 1000); } void blink(const ...
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38 views

Peculiar relay behavior from POST

I am trying to toggle on/off between two separate HTTP request. One submit button to turn it on, and another separate submit button to turn it off. I expect the device to launch in the off/low 0V ...
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3answers
148 views

Run multiple function with different argument/return structure by one function pointer

Edit: I tried a simple code in Arduino IDE which should've done in the first place instead in doing it in a desktop compiler. Because the results are different by experiment. In the desktop C compiler,...
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2answers
44 views

How to move a servo with a function

Im currently moving a servo from one side to another by using the typical for loop like this: int lightON = 180; int lightOFF = 90; if (buttonState == HIGH) { digitalWrite(LED, HIGH); for (pos1 =...
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1answer
142 views

Serial.print skips or hangs inside a “if” statement. Trying to call a function VIA serial uart

I have two microcontrollers talking to each other using serial UART pins. Now for some reason which I can not figure out why... doing a Serial.print() does not work in an "if" statement. And ...
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1answer
33 views

Input state is stuck HIGH when function called using input also uses same input to call another function

I'm writing a choose-your-own-adventure style project for a class project. My Arduino Uno is set up with a 16-digit LCD display and two pushbuttons with pulldown resistors. I'm wanting each function ...
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1answer
22 views

Serial doesent work when calling function from timer

You can try the code on your arduino UNO to better understand what is hapening in serial monitor! I want to calculate jacobian matrix from rotation matrix! float jakMATB[3][3] = { {0, 0, 0}, {0, 0, 0},...
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243 views

How do i improve this Code? (or how to pass a Char String into a Function to behave like a Variable)

Sorry i am a beginner and amateur when it comes to coding, can somebody help me to make the code inside the loop() less "monkey-like" by using a proper function? I have tried a lot and at ...
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1answer
78 views

Passing a time_t array as a function parameter

I'm trying to log reconnections and disconnections of a network. For that I've created 2 time_t arrays to store such occurances: const int logSize = 10; time_t conLog[logSize]; time_t disconLog[...
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1answer
415 views

How to get variable from callback function?

There is a library davetcc / IoAbstraction. The only library working as expected with my rotary encoder. The problem that on rotation I can only see serial output with position data, but I cannot get ...
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1answer
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A word after function arguments braces

I'm just reading through a header files for task code in ESP8266 SDK. I found this line and wondering what does the word PRIVILEGED_FUNCTION after the function arguments braces means ? void vTaskDelay(...
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2answers
358 views

How do you remove an item from array arduino?

Is there a way that can change {3, 5, 3, 6} to {3, 5, 6} with a function? I checked all the arduino forums but they don't give the answer i need (just delete 1 item from an array with a function like ...
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3answers
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Formatting variables from a variadic function

I have a function that concatenates a print line, however I am having trouble getting some of the strings to format correctly. Using Serial.print formats the output from keypad.getKey() correctly, ...
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1answer
130 views

Error taking address of temporary array when passing compound literal array

I have an Arduino sketch that passes an array into a method as a compound literal, but for some reason I keep getting the following error: void setup() { } void printConcatLine(char chunks[][20]) { } ...
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0answers
52 views

Tapered log potentiometer to linear formula

I have a tapered log 10K potentiometer. I would like some function which returns tapered log value to linear values. The potentiometer is a slider. When connected to the Arduino the wiper displays the ...
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2answers
51 views

Why is function mentioned in global declaration?

I came accross this code for writing data into EPROM in arduino. Why is void printTemp(); void clearEEPROM(); and void writeTemp(); functions are mentioned in global declaration? How will this help? #...
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1answer
633 views

What does []() argument in function mean?

I am working in ESP8266 AsyncWebserver library and have been using this [](parameter) as an argument to some functions as shown below but does not really know what it means. Being a neophyte I am ...
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1answer
49 views

Boolean function call with character pointer input - dont understand how to get updated pointer value

Thank you for everyone's help in trying to find a solution. This library I'm working with was prewritten and is one of the most buggy hardware libraries I've had the misfortune to use. I have now ...
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3answers
47 views

problem using one function to blink different leds

I wrote a function to blink an led using millis and want to blink multiple leds with the same function but with different delay intervals. When I call this function thrice to blink 3 different leds, ...
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1answer
100 views

Remove blocking delay() toneMelody function?

I would like to change the delay() into a nonblocking function in the code below. I've implemented it (a part of a tutorial from arduino.cc) in my code, but the delay() is blocking the rest of my code....
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How to properly pass struct as argument? [duplicate]

This is my first question! i'm sorry if i'm doing something wrong. I'm trying to write a code that blinks some leds, but i cant quite work out how to use structs as arguments. This is the code: void ...
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1answer
58 views

Running commands from string

I have a string: string s="digitalWrite(8,LOW);" Is there any way to run it as a code?
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1answer
55 views

Function pointers that call one function

I'm reading a library file timer.h for STM core library that I just installed in Arduino hardware folder. Of course, there has to be a lot of questions for me as a beginner about many approaches/...
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2answers
361 views

7-Segment Display with WS2312B and FastLED

I thought of the idea of using the WS2312B LED strip to drive a custom 7-Segment display. The project will require a large number of these displays, and driving them with a single Arduino (I'm ...
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1answer
972 views

Is there an Adafruit function to invert the colors of my screen for Arduino language?

I am trying to invert the color of my OLED display screen once a button is pushed. I have the button situation figured out but I can not find a function that inverts the color. I am using these two ...
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1answer
251 views

Function to control servos

I'm trying to control 6 servos while writing a lean code. I think the function call isn't correctly yet and I think that the variables (pos_n, open_n, servo_1) in the for loop do not get inserted, but ...
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0answers
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Get value from protected member of class

i'm really new to Arduino. I have Arduino Mega, a USB host shield and a barcode scanner. I'm using this library >> link and modified it example so barcode scanner worked (Got it from here) to read ...
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1answer
62 views

Protecting variables and functions within a library that has no class

If you want to have functions within a library that only the library itself should be able to use or variables that shouldn't be accessed from outside, you usually make them private by writing this in ...
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1answer
30 views

Compute the size of an array that was passed as a parameter to a function

When passing an array to a function, you usually pass the length of the array along with it. You can compute the size of the array with sizeof(myArray)/sizeof(myArray[0]), which works just fine. ...
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1answer
85 views

Trying to create a delay function whilst performing other functions, using Timer.h libraries. Arduino uno

I am having a compilation error saying invalid useof template-name 'Timer without an argument list.
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4answers
550 views

How do arrays work?

It's been days now I'm trying to figure out how arrays work in Arduino IDE. For better understanding, I assembled some pieces of code I found here and there to write this sketch: #define arrayLength(...
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4answers
332 views

Why do most arduino function return a -1 instead of a 0

Many arduino functions return -1 if something 'fails'. Serial.read for example returns -1 or the infamous ÿ when this function is called while the serial buffer is empty. As embedded C progammer, I ...
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1answer
37 views

How to access variables by variable? (I.e. variable variables?)

Can Arduino handle variable variables? function getLetterCode(char input) { int letter_a = 17; int letter_b = 42; int letter_c = 50; return letter_$$input$$; //pseudocode } This is ...
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676 views

How to return Char Array Value in Arduino IDE Function?

Function char* getConnectDetail(int starting){ String data; for(int i=0;i< 1024 ;i++) { if(EEPROM.read(i+starting) != 0){ data += char(EEPROM.read(i+starting)); } } int ...
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1answer
3k views

Cannot convert 'int (*)[size]' to 'int**' [closed]

Analyzing this and this answers under Arduino, which should be the proper way to pass a 2D array into a function? The function should be applicable to different sizes of 2D arrays. // NOT COMPILING ...
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2answers
1k views

How can I pass multiple variables to a function? [closed]

Using the FastLED library, I want to light up multiple lights at once. Currently I am passing in just one light to the function. spell( int LEDNumber ) { FastLED.clear(); leds[LEDNumber] = ...
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1answer
47 views

Remove Function at Preprocessor Time

I have a single function for debugging messages, used through all the project. When KEYDEBUG is defined as 1 or 0, the function is enabled or disabled as required. #define KEYDEBUG 0 void debugging(...
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2answers
533 views

can't return float value from function

I want to put a 2 seconds delay to temperature reading but the millis() delay is not applying. #include <OneWire.h> #include <LiquidCrystal_I2C.h> #include <DS3231.h> #include <...
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2answers
109 views

Fail to return int value from a function

I have created myJSON library to simplify read and write values from/ to FLASH of my ESP8266 NodeMCU/ Wemos Mini. I do not want to "mess up" the question, posting my entire code/ library - but to try ...
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1answer
58 views

Strange artifact in writing to serial while executing loop

Hope you can see this. https://gist.github.com/DevilWAH/60ad144d2858f53845ac2e80f84bb070 The main file in this is "morse-led-rfid" which is taking reading data of an RFID tag and then displaying ...
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2answers
119 views

Is it possible that function will get a parameter that can be int OR char?

I'm trying to create a function that enters a key/value into a JSON file. But, since value can be an int or char, I don't want to create 2 functions for each type. Is there a way ? void setValue(...