Questions tagged [variables]
Variables are used to store data in a sketch/program.
162 questions
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How do I change what variable I am changing based on a separate number?
I am trying to change thing2 if I input 0, and thing3 if I input 1. I don't want to just have if/else to determine if I should be changing thing2 or thing3 because I want this to be more dynamic than ...
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1
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Declaration of global variables in separate file: compiler conflict
So I have:
1/ My myapp.ino file, that includes src.h (implemented in src.cpp). Compiled for Arduino Uno.
2/ I also have a unit-tests.cpp file that is meant to test functions in src.cpp. Compiled for ...
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1
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958
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Multiple definition error in STM32CubeIDE
How do global variable declarations work?
For example:
In file1.c I am defining:
#define volt_add 0x20
uint8_t vol[8]= {0x53, 0x35, 0x05, 0x22, volt_add,0x00,0x00,0x00};
uint16_t EM_vol;
I need to ...
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1
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2
answers
114
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converting comma delimited Serial message to 7 Unsigned Long variables
Working on a project where I get an input where its a comma delimited string like:
"255,10000000,42949672950254,12,22".
and then the numbers (no commas), would be split into 6 Long ...
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0
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1
answer
1k
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how to "skip" one parameter of a method with a default value letting it use it's default value, but change parameters after it [closed]
lets say we have a function like this(fictional):
function1(int Z, int X, bool Y=true, int Count=10, int ID=1,bool TeaTime=false);
And I want to run this function, but I want to change all parameters,...
- 254
0
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2
answers
314
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IsTimeSet library - Assign variables
i get the current time with the example code istimneforset, everything works fine.
now i want to get the current time from the function "Serial.println(timeClient.getFormattedTime());" and i ...
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1
vote
1
answer
280
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Conditional assignment of array
I have some really long global variable arrays filled with data.
There is a single function that processes the data. The function works on only one array everytime. This arrays value changes every ...
- 1,435
0
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1
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261
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What's the difference between CloudTemperature, CloudTemperatureSensor and Float data types?
I have a SHT30 sensor for Wemos and I am learning to use Arduino IOT Cloud.
I use float data type for my temperature variable but I see two more data types:
CloudTemperature
CloudTemperatureSensor
...
- 448
0
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1
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95
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Wrong use of memory?
Probably I'm doing something wrong.
I'm writing an Arduino sketch for ESP32.
Among the others I have this function:
#define HDR_MAX_LENGHT 4
#define CMD_MAX_LENGHT 5
#define ARG_MAX_LENGHT 5
#define ...
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-2
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1
answer
851
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how to save float with 3 decimal places [duplicate]
i am transmitting sensor data from my atmega328p to my esp8266. The Sensordata has 3 decimal places. The esp8266 sends this data to my pc and there I see only two digits. This is because the data is ...
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0
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1
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86
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Inconsistent behavior of include statements?
This question deals with fonts. Well, actually, singular include files with constants that form bitmap fonts or images for LCD or OLED displays, such as this one: https://github.com/ThingPulse/esp8266-...
user47164
0
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3
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2k
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How do I modify the value of a variable when I press a switch
I am new to arduino and I want to make a project where I have a motor spinning clockwise then when a button is pressed it spins anti-clockwise and if it is pressed again it goes back to clockwise etc.....
1
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1
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449
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1 global variable consuming 19% of memory
I am working on a simple project on talking to the serial monitor, and my only global variable ("int" type, named "incomingByte") is consuming a lot of memory. There is no problem ...
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1
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113
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Initializing an object as class member resulting in linking error?
I'm a little dumbfounded as to why this isn't working. I keep getting the following linker error:
In file included from src\ac.cpp:1:0:
src/ac.h:9:21: error: expected identifier before numeric ...
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2
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1
answer
3k
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Space taken by Global Variables
Using Nano's for small programmes I get compilation reports about the amount of space taken by global variables.
On a typical progamme it says something like Sketch uses 16316 bytes (53%) of program ...
1
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2
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3k
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Can bool variable be NULL
I want to know if bool variable can be null, or it must have to be true or false:
Base on Arduino description:
A bool holds one of two values, true or false. (Each bool variable occupies one byte of ...
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2
votes
1
answer
362
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Global Variable not updating…
I'm building a small project to maintain a copper plating tank's temperature and filter pump duty cycle. I'm using the Adafruit Feather platform to hold an 8 segment matrix coupled with a Teensy 3.2 (...
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2
votes
2
answers
1k
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How to write nonblocking code, for polling sensor at 100 Hz
I'm using this piece of code to try to poll an IMU sensor at 100 Hz (for a AHRS sensor fusion library).
void loop(void)
{
// nonblocking code variables
static uint32_t last_ms;
uint32_t ms;
// ...
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1
answer
156
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How to deal with global variables in a program which has more than 5 functions and every function accesses them without any problem? [duplicate]
I know that using Global Variables in programming may create lots of problems in long term , like , Bugs , Lags and more . I am working on a program which has more than 5 functions which need to ...
1
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1
answer
2k
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nRF52 non-volatile storage/recall of a variable - is there a simple solution?
I have an Arduino program written for the nRF52 with which runs for a pre-set time-value (i.e. 2 minutes) before shuts off automatically. The variable time-value can be changed via BLE-write by the ...
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1
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0
answers
118
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Why does this piece of code overflow at 255?
Im having a problem where i got unsinged long variable and i need to increment it in eeprom everytime setup starts and it overflows at 255 back to 0.
unsigned long NumberOfBoots = 0UL;
#define ...
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0
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1
answer
908
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does EEPROM reset itself when a new code is uploaded?
I have a Nodemcu with which i'm doing a project. So whenever there is a power loss i want values of some of the variables to not be reset, because of that im trying to store the values in EEPROM of ...
1
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2
answers
993
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How to reset a variable just before entering a function? [closed]
I am facing a problem where the if condition in the function waterNowrun is able to execute once after the program starts as the variable v is 0 at the start, but upon starting it again the if does ...
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0
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1
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107
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How to make ultrasonic and light sensors detect whether a person moving in or out [closed]
I am trying to make a circuit that will be used for turning on a light whenever there are 1 or more people in a room. I need to add to a variable counter when someone enters and subtract when someone ...
0
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2
answers
412
views
why can Arduino variables of int type contain a value such as A2
How come the following statement is true:
int inputPin = A2;
I thought int variables can only hold integer numbers. Is the A just a representation of a number?
Thanks for any help
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0
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1
answer
54
views
non asssign variable using by for in loop() can remeber last value. what happen here?
I modify this code from my friend and it look strange.
void setup() {
Serial.begin(115200);
Serial.println("reset");
}
void loop() {
for (int d; d <= 32767; d++) {
...
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1
vote
1
answer
955
views
using a variable to index an array
I'm using the keypad library to return a number 1-9. (im fairly sure this returns an int)
I have an array (data) showing the state of each button press.
so i would like the number returned by the ...
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1
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1
answer
1k
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Printing vairable with U8GLib
I have this code that takes temperature and humidity values from a DHT11 sensor and number of faces from an external python code and prints them on an OLED screen but instead of values of variables it ...
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1
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0
answers
1k
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Nextion won't update text using data passed in Arduino Uno serial print
Q: Is it possible to send data in variables from Arduino to Nextion through SerialPrint? If so, what is the correct syntax?
I have an Arduino Uno connected to a Nextion NX4024T032 and a Sunfounder ...
1
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1
answer
528
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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1
vote
3
answers
174
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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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1
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1
answer
172
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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2
answers
3k
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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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1
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341
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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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1
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0
answers
65
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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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0
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2
answers
513
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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1
vote
1
answer
697
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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0
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1
answer
475
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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 ...
0
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1
answer
460
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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 ...
3
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1
answer
13k
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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 ...
1
vote
1
answer
745
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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0
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1
answer
499
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 ...
- 107
2
votes
2
answers
881
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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0
votes
1
answer
364
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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1
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230
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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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0
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1
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174
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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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4
answers
1k
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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(x)...
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1
vote
2
answers
55
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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 - ...
1
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2
answers
7k
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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 ...
0
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1
answer
89
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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