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Questions tagged [variables]

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

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49 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
34 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
98 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
26 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
132 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
34 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
30 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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0answers
30 views

Accel Multi Stepper - Array for timelapse operation

I am trying to run 2 cameras for timelapse. I can do this with a single stepper: void doSteps(long steps) { calcSpeedStepper(); digitalWrite(sleepPIN, HIGH); stepper1.setCurrentPosition(0); ...
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1answer
140 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
144 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
126 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
115 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
543 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
46 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
172 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
39 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
88 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
68 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
66 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
48 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
46 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
221 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
105 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
27 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
715 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
66 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
4k 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
160 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
214 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
160 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
45 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
489 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
2k 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
3k 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
29 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
95 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% ...
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2answers
3k views

Fill an Array with Values

I have a function in which I change the pinMode on many of my Arduino's pins based on a passed in mode. I first construct an array of bytes specifying each pin to be an input or an output and then I ...
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4answers
1k views

Global variable won't update inside void loop arduino

I need to update my global variable once I get a 'overdtrue' response and light up my LED but only my LED is lighting up but my global variable is not updated. Here is my code int x = 0; void loop()...
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1answer
1k views

Why using static volatile for variables and only static for arrays in TWI library?

I want to know why to declare variables with static volatile and arrays with only static in TWI library? For example; static uint8_t twi_masterBuffer[TWI_BUFFER_LENGTH]; static volatile uint8_t ...
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3answers
3k views

How to use a coma as the decimal separator?

I have a LCD that displays a float variable. I would like to show a comma instead of a dot as the decimal separator. float temp = 23.50; lcd.setCursor(0, 0); lcd.print(temp); I want to show 23,50 ...
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1answer
123 views

Error declaring two-dimensional array: 'x' was not declared in this scope

I'm trying to declare a 2-D array where each letter in the alphabet is keyed to a corresponding LED in my LED strip. But when I try to declare the array, Arduino flags the values and gives me a "not ...
0
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1answer
381 views

Space needed for local String variable

I tried to run this code on my Arduino Uno clone (which has no function so far and is a shortend version of my programm): String rules [16][5] ={ {"B0 B5", "", "", "cs S0", "", }, [...] }; ...
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1answer
151 views

Interrupt volatile variable doesn't work as expected

Please examine the following code. volatile uint8_t myVar; void setup() { attachInterrupt(digitalPinToInterrupt(2), isr, FALLING); Serial.begin(115200); } void loop() { myVar = 0; while (...
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1answer
505 views

How do I properly convert a pointer (uint8_t* or void*) to a “normal” integer?

I'm writing a program for arduino that needs dynamic memory allocation frequently, but as I don't want the memory to get fragmented, I'm also writing a "memory handler" for it. This memory handler ...
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1answer
43 views

Variables displayed incorrectly

I am making a keypad and when I try to save the buttons that were pushed they reset back to zero. int tmp = 1; int digit = 1; int a = 0; int b = 0; int c = 0; int d = 0; int code = 0; void setup() { ...
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1answer
44 views

Allocation, initialization and scope

I realized I don't fully understand how Arduino code handles variable lifetime. My tendency is to keep variables in the narrowest scope (which I realize isn't as important in Arduino code, but, habits....
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4answers
2k views

Send serial command and wait for reply

I am new to Arduino and have tried all kinds of code for attempting to achieve this. None with any luck, however. I feel that it should be a relatively easy task and therefore, figured that someone ...
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2answers
218 views

Is this assignment valid or needs casting?

I have this assignment and while i don't get any error not even warning from the compiler. uint16_t Buffer[40000]; for (int n=0; n<40000 ; n++){ Buffer[n] = (0.99 * cos(((2.0*PI)/40000)*n); } ...
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2answers
197 views

Is it ok to declare variables inside timer interrupts?

I am building a real time audio application using the Arduino DUE. This application needs big arrays like: uint16_t sDelayBuffer0[46000]; The Due has only 96kb of RAM available so this array just ...
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3answers
1k views

Sizeof variables and Due's RAM

I set out to see how much space some arrays have. I used this test code bool state = false; uint16_t BuffA[46000]; uint16_t BuffB[20000]; uint16_t BuffC[20000]; uint16_t all = 0; void setup(){ ...