Questions tagged [variables]

Variables are used to store data in a sketch/program.

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1answer
60 views

Change/declare a constant in setup and use it in loop

I want to change or declare a constant in the setup() and then, I want to access it in the loop(). I have searched a lot, but the only questions I found could be solved by declaring the constant in ...
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3answers
110 views

variable name standards, e.g best method to send motion_detect=true

I am working with some sensors and sending data to a public web server via http, I was thinking this server can be possibly used by more people to send their data and server displays a chart. I was ...
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1answer
134 views

I want to create 10 levels with one button but this code shows only level 1?

#include <Adafruit_NeoPixel.h> const int PIN = 4; const int NUMPIXELS = 10; const int BUTTONPIN = 6; int buttonState = 0; int PINState = 0; int level = 1; int dt = 100; Adafruit_NeoPixel pixels(...
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2answers
2k views

Can you use Serial Port as a variable?

I am doing a project where, for troubleshooting reasons, I find myself often swapping components to different serial ports. Maybe one time it's in Serial, then in Serial1, maybe I need to try if ...
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1answer
233 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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0answers
38 views

Having a bunch of global variables or calculate them on the go on an Arduino, as far as memory is concerned

So I'm new in the arduino world but I have a grasp of object oriented programming, and decided to write a little library for running games on an arduino mega using a display. My question is, I'm ...
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2answers
92 views

Convert character to Integer while leaving encoded

I have two characters, that I get by Bluetooth. char a = SerialBT.read(); char b = SerialBT.read(); According to the Arduino Reference, decoded data stored in a char gets encoded to ASCII text. I ...
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1answer
50 views

Global variable changes its value when loop starts again

I have a problem with the global variable calibrationValue. It is initially set with the correct value and is also displayed correctly in the output. As soon as the loop function is restarted, the ...
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1answer
36 views

Storing IR Sensor value not working

This is my first time working on Arduino for my project and I ran into an issue. I'm trying to make a very simple Vending Machine. Coin or any obstacle passes in front of the IR sensor and based on ...
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1answer
32 views

What does display.setSegments(&segto, 1, 1); do?

I am using a TM1637 display for my Arduino Uno. The goal was to just light up one point of the colon in the middle - what seems to be kind of impossible to accomplish. During research I stumbled over ...
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1answer
64 views

Getting enum name from enum instance [closed]

Hello Arduino Stack Exchange, I have an an enum instance called state: enum States { SLEEP, AWAKE, CRAZY } state; States state = SLEEP; I would like to convert the value of state to a String so ...
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1answer
153 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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1answer
109 views

Scope of RtcDateTime object when declared outside of a function

I'm trying to merge 2 Arduino samples, in order to be able to use DS3231 RTC module with ESP8266 WiFi simple web server. My RTC library is this: https://github.com/Makuna/Rtc/wiki Generally, to code ...
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2answers
150 views

Using the same variable between if-statements within loop()

I wonder if there is a good way to use the same variable value between two different if-statements within the loop(). Within the Servomotor section of the code, I want to use the value from the first ...
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1answer
31 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
60 views

Variable sets to 32767 - MATLAB Arduino

I am running out of ideas of what may be causing this problem, and I would appreciate some help identifying anything I am overlooking. Quick Problem Summary A variable gets set to 32767 quite often ...
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1answer
51 views

How to merge two GPS coordinates without losing decimals

I want to take the GPS coordinates like 42.1234 per 22.1234 and merge them as a string, with a separator character: 42.1234 x 22.1234 But using this code: gps_string = (String)gps.location.lat()+' ...
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4answers
406 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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2answers
28 views

How to make procedures triggered remotely

I am installing lights in a model train and there are multiple prototypical lighting procedures that need to be activated. The lights are connected as follows: Headlight Top - Pin 1 Headlight Bottom - ...
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2answers
2k views

How to display float variables on oled display (0.96'')

I have a similar problem than the discussed here : How to display variables on 0.96" OLED with u8glib library? I'd like to know how can I show float variables in place of int variables. What ...
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1answer
36 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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0answers
32 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
622 views

Accelstepper - how to switch from fullstep to halfstep in loop?

I am using Accelstepper library to control a unipolar stepper motor. In my project, I would like to run the stepper in full-step mode when I need speed and in half-step mode when I need precision. As ...
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0answers
616 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
432 views

what is the difference between array of uint16_t data versus an array of uint16_t variables?

I've been struggling with weird behavior, crashes and general problems when trying to use an array of four uint16_t groups of data. When I create four separate variables and load that into an array, ...
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3answers
634 views

I want to reset a variable after each 1 second on an Arduino

I want to reset this counter variable which I created after each 1 second, but I don't want to disturb the if statement. Here is the code: int button=A0; int val; int count=0; int presss; void ...
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3answers
636 views

Global or local

I'm new to Arduino and embedded, but understand that it is often better to use global instead of local variables (such as here or here). I have this simple code (from here): //Libraries #include <...
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1answer
83 views

What is the easiest way to count how many global variables are in your sketch code?

I have a fairly complicated sketch with about 1k lines of code. I should also say that I'm not a programmer by trade... As I go over my code and try to make it more efficient, it'd be good to know ...
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2answers
274 views

Make a float using integers [closed]

I want to make a floating point number that has only one decimal point. I have separate integers for both side. Ex: int n1 = 8; int n2 = 2; I want to make 8.2 as float value using separate ...
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1answer
46 views

What do the charactors “ '/2' ” mean in the variable declaration?

I'm working on an RS485 project, In the CPP file there are const variables declared in the following manner: #include <RS485_protocol.h> const byte STX = '\2'; const byte ETX = '\3'; What ...
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2answers
121 views

Assigning array variables to int variables

I need to control thousands of rgb leds.To make animations I want to assign led numbers(addressable led strip) to arrays.For example floor[2]room[14]=106 106 is the number of led,there are many floors ...
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1answer
205 views

Global Variable does not Change when Value is set within Boolean Function

I have a boolean function which contains a string. In my main project this string is extracted from a website using an ESP8266 which is compatible with the Arduino IDE. I need to convert this string ...
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1answer
85 views

Sorting voltage data from pin A0 to 3 variables (ranked)

I don't have any code for this yet but I would like some ideas on coding it. I have a directional antenna that is rotating at a slow speed and a ham radio connected to the antenna. I have an output ...
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1answer
80 views

How to deal with this array correctly?

I am using a led strip WS2812b, an ESP8266 (NodeMCU 1.0) and a gesture sensor APDS9960. I want that when I move my hand from left to right and from right to left I change the colors of the strip of ...
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1answer
47 views

Hex output although I always define integer

Code below is to read 4 thermometers and use values to turn on or off the heaters (I'm stuck at reading). I'm reading and displaying temperature very well, but it comes to the problem, where I want ...
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3answers
1k views

Do some variables not hold their value when a while loop is exited?

Sorry if i'm asking too many silly questions but i'm really stumped on this one. I understand if I set a variable inside a loop that that variable won't be within scope from the outside of the loop. ...
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2answers
114 views

Run piece of code based on a feature

I am an engineering student completely new at using Arduino so my following question might be silly but still. I do not think you'll need to get the entire code so I am only going to expose the idea. ...
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1answer
28 views

Variable that holds the users input doesn't empty itself, so the program only works once

This code seems to function, but only works once before I need to press the reset button. Otherwise, it repeats the same error message. It might have something to do with emptying the String variable. ...
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2answers
1k views

Locally declared variable takes up global variable space in dynamic memory/SRAM

I'm trying to make my Arduino Uno control the air conditioner by recording the raw IR signal of several of the AC remotes temperatures using AnalysisIR. However these IR codes are quite long (array ...
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1answer
879 views

warning: variable 'b' set but not used

I got the following error: warning: variable 'b' set but not used. I think I do a really small thing wrong but I can't figure out what it is. #define array_size(array) ((int)(sizeof(array) / sizeof(...
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1answer
5k views

Saving a .txt file to SD Card and Reading each content data to txt file then save it to a variable

I am new to arduino I am trying to create an arduino project that Saving a .txt file to SD Card and Reading the txt file then save it to a variable data type "Long" named 'savednum'. I had ...
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1answer
325 views

Arduino variables loaded from SD card

I am trying to load some variables from an SD card on the start up of my arduino Uno. I have been given some advice but am unable to communicate at the same hours. Using this advice, I have the ...
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1answer
455 views

Is there any way to group variables like group.variable as you can in Java/Delphi

I'm writing a sketch which does some calculations on measured variables, and it's based on a similar program written in Java like c = A.Ux + B.Uz; Where A&B have various parameters Ux,Uy,Uz etc In ...
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1answer
243 views

Arduino - use print(.., DEC) to save into variable

I am using: Serial.print(rawCodes[i - 1], DEC); to print into serial monitor, but how can I save (rawCodes[i - 1], DEC) to save into variable?
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2answers
46 views

Question about Variables [closed]

is there a way to use a previous assigned value to variable to adjust the step motor? what i mean is: example: Sensor reads 100 degrees so Adjust the step motor to 100 degrees and hold, then after ...
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2answers
822 views

How can I declare global array with its length stored in EEPROM?

I am working with Arduino UNO connected with BV4612 display. I am working on a simple code that controls several water pumps. Each pump has several modes it can run in. I store these modes in an array....
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1answer
3k views

Arduino resets variable every loop

im new to arduino and have a problem currently with my project on sun tracking. The problem is that every loop it resets my variable back to 1 or whatever i set it. I have 4 photodiodes working ...
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1answer
6k views

Call by reference

I am trying to learn 'call by reference'. I want to call a function fcn1 from the main loop and pass a reference of the local variable var to the function fcn1. Next step is to call a second function ...
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1answer
31 views

variable doesnt have a type name

Why can't i assign the value to a variable outside the function? void setup(){} int a; a=12; // WHY IS THIS GIVING ME ERROR void loop(){ } Why the line a=12 gives me an error? Thanks!
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3answers
143 views

Is there a way to put multiple integers in a method? [closed]

I'm working on a project that has 3 RGB LEDs. I want to make a simple method that I can call to control the LEDs for example: showColor(left, 255, 0, 50); Which would light up the left LED at 100% ...