Questions tagged [data-type]

Identifies the size and nature of information held by a variable in a program. It is language-dependent. Examples for C/C++ include: `int`, `float`, and `char`.

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4answers
4k views

Multiplication, division. What is wrong?

const unsigned long C1 = 30 * 1000; const unsigned long C2 = (300 * 1000)/C1; // must be = 10 void setup() { Serial.begin(57600); Serial.println("\n-------"); Serial.print("C1 = "); Serial....
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3answers
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What Arduino data type allows decimals?

This probably sounds dumb, but I am not getting any clear answer for this. What data type allows a reasonable amount of decimals?
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1answer
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Can't create an array of type const char*

I have something being returned as a const char* and would like to save it to an array. I've tried this: const char* book[amtBooks] = ""; and get this error: error: array must be initialized with ...
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3answers
98 views

Is the strange problem I'm having to do with comparing floats?

I have a timer interrupt that controls a stepper motor, on an UNO board. In the interrupt handler it checks the speed of the motor and compares it to the target speed. This allows the motor to ...
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3answers
195 views

How to map 6 bytes of raw data to long long type?

I'm trying to solve some problems for a contest, and I have a problem with it. I have to implement a function that has 3 arguments like this: void foo(unsigned char* A, unsigned char* B, unsigned ...
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1answer
390 views

Casting custom shared_ptr object

I am using custom shared_ptr class for some program on Arduino, and I need to do something like this: shared_ptr<Base_class> b_ptr; shared_ptr<Child_class> ptr((shared_ptr<Child_class&...
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1answer
427 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
3k views

Arduino: load variables with values read from SD card

I am having a bit of trouble loading values stored on an SD card and assigning them to variables within my program. I can achieve this as one big block of data, but would much prefer them to be saved ...
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3answers
1k views

Sending struct from Arduino to Raspberry Pi - wrong types

I'm using Raspberry Pi and Arduinos for my home automation project where Raspberry Pi is the controler of Arduino nodes. I use nRF24 wireless transceivers to communicate. My problem is that when I ...
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2answers
56 views

Comparing custom variable type definitions

In a library I am using with an OBD adapter, they define a public function to get the state of the OBD connection using some strange (and, in my opinion, useless) custom defined variable type: // ...
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3answers
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How can i get rid of the error “cannot convert 'String' to 'const char*'”

I want to get this code to recognise different commands and be able to parse the rest of the command, fore example I send "/sleep 5", and it will sleep for 5 seconds. However, I keep on getting this ...
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1answer
136 views

DS18B20 sending variable via Enthernet shield

I am trying to send temperature read from DS18B20 to a web server. I know two things: to read a temperature, and to send something to web server. What I don't know is how to convert float that ...
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1answer
5k views

Put integer and double into char array

I want to print text and numbers mixed in a table with Serial.print(); from a char array. My problem is the conversion between the different data types. My idea is to print the data of the rows in a ...
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1answer
750 views

Store values in array

I'm trying to implement the "BNO055 9 Axes Motion Shield". There is an existing Arduino sketch GitHub that reads out the Euler data, I changed it a bit to print out quaternion data. #include "...
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2answers
7k views

Converting (char*)variable to int

I have the following code: uint8_t buf[1]; uint8_t buflen = 1; if (driver.recv(buf, &buflen)) // Non-blocking { int i; // Message with a good ...
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1answer
2k views

RF receiver for integer only, how to cast uint8_t to int?

I'm using the RadioHead library with ASK Driver to transmit/receive data with generic RF modules. It works fine, but I'm lacking some knowledge in programming the code to use the data received. Most ...
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2answers
1k views

How can I write an integer to a Mifare RFID card using the RFID library?

I'm a beginner to C++ and I'm clearly missing some fundamental knowledge of data types. As such, I'm struggling to adapt the examples in the miguelbalboa/rfid library to my use case. I'm simply trying ...
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1answer
6k views

Receiving hex data from terminal [closed]

I am trying to transmit serial data from terminal to Arduino and I want to reconfirm that its the same data. But I am not able to get the right answer. I want data to be HEX. I want to check only the ...
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1answer
135 views

Determine whether a variable is of an arithmetic type

Is there a way to determine whether a variable is of an arithmetic type or not? arithmetic: integer, floating point numbers, boolean values not arithmetic: pointers, references; e.g. strings, and ...
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2answers
2k views

Const data optimisation for Arduino

I'm taking a course on Arduino Uno programming and on today's talk I heard that the const data is optimized by Arduino, so that it occupies less space than the actual data type (namely, a const int ...
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3answers
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Why char 0x80 == 0xFFFFFF80?

As far as I know a char is an 8 bit variable void setup() { Serial.begin(9600); } void loop() { char x = 0x80; if(x != 0x80){ Serial.println(x, HEX); } delay(1000); }
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Testing ID and Serial Communication (Update)

Here is my challenge: I have to create a sketch where I would have a prompt asking the user to enter an ID. If it is successful, it would turn on the green LED and response with "Hello, your name is ...
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2answers
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Unable to compare two integer values in Arduino Mega

I wrote Arduino code (code is given at the end) to compare two integer values. The steps I took was: Give input to DC motor to rotate it using serial port. Input was: G254 Then I store it in XX ...
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3answers
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Having issues with Arduino + Bluetooth

I am working with a combination of Teensy++ 2.0 and Sparkfun Bluetooth Modem. The Arduino program, inside the loop, continuously reads a sensor value. If the value read is above a threshold, the ...
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1answer
5k views

String to unsigned long conversion

I'm trying to use strtoul() to convert an Arduino String to an unsigned long (like the return of millis();) using the following code snippet: unsigned long foo (String time) { unsigned long mili; ...
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1answer
5k views

What is causing this 'narrowing conversion' warning?

Because I'm still figuring out 'Arduino C' I leave all warnings on. Recently I got this one: narrowing conversion of '(int)(((unsigned char)bx_0) | ((unsigned char)bx_1))' from 'int' to 'const byte.....
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2answers
159 views

Arithmetic types in Arduino

I'm looking for a complete list of the arithmetic types in the Arduino framework. On the Internet I found various incomplete lists: sometimes there is short, sometimes word, but other types are ...
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2answers
253 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
107 views

character input for an integer variable? [duplicate]

Im trying out the code found here , let me quote the section of code that bothers me. // set pin numbers for switch, joystick axes, and LED: const int switchPin = 2; // switch to turn on and off ...
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1answer
503 views

What datatype is the names of the analog inputs?

I am writing a code for an automatic garden, and for this, I will use an array of sensors. I want to represent each plant as a class, and so one of the private variables will then be the sensorID, the ...
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1answer
2k views

Modbus slave data into word

I have simple code. The library downloaded from github:smarmengol/Modbus-Master-Slave-for-Arduino. I wanted to store floating point. In the code blow, I type casted to integer value. As I know ...
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2answers
1k views

Having problems with I2C - Slave is receiving “b ~ ,,,”

so I'm facing a pretty large problem. I'm experimenting with I2C and using one Arduino that acts as a countdown timer to send the current reading on the timer to another Arduino. I'm pretty new to ...
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3answers
2k views

A library for manipulate Intel Hex data?

For a project i need to extract some data from an external eeprom and then store it somewhere. Suddenly after some manipulations (not necessarly with Arduino board) i need to put them in an external ...
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2answers
5k views

Convert uint8_t array to ascii character for serial transmission

I am trying to send packets of via bluetooth data that include 6 bytes read from a sensor and stored in a uint8_t array. Instead of sending over the data as numerical digital, I would like to send the ...
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1answer
146 views

Understanding SevSeg

I need to write a library for a display I created with eight segments. So, I decided to try to use SevSeg (https://github.com/DeanIsMe/SevSeg) as a starting off point. It can't be that different, ...
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3answers
805 views

How is a local variable address retrieved/returned inside the CPU of Arduino?

How is the address of a local variable retrieved in Arduino's ATMEGA328 micro-controller? Lets say somewhere inside the main we have lines as: int x = 5; //a variable declared and value of 5 stored ...
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2answers
137 views

How does an 8bit MCU make use of data-types over 8bits?

how does an 8bit MCU handle 16bit output? How does an 8bit MCU store values higher than 8bits? I am using an attiny, on an adafruit trinket. and other 8bit MCUs. http://www.atmel.com/devices/attiny85....
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3answers
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How can I convert Arduino String to C string type?

I got a String which as I understand is an Arduino object, and got some C++ code: #include <Wire.h> #include <LiquidCrystal_I2C.h> #include <string.h> LiquidCrystal_I2C lcd(0x20,...
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1answer
434 views

What is the datatype of the pinMode function?

I just tried it, but the Arduino IDE crashed, I hope its not related. I want to declare a datatype like this: int a = pinMode(pin, OUTPUT); or something like that, but I'm not sure what datatype the ...
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2answers
197 views

How can i do something like multi threathing in arduino?

I am checking for ways to implement multi threathing in Arduino, I have also tried using the library TimerOne but it doesn't seem to work, what I'm trying to make is an Arduino application then, every ...
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1answer
3k views

What does 16u and 128u mean?

The below is a snippet of a code for operating SI4455 Rf module with Arduino. I have some doubts which I'd like to seek some help in clearing. byte numOfBytes = *pSetPropCmd++; if (numOfBytes &...
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2answers
198 views

how to use an object of a class within that same class? [duplicate]

I want to write a tree data structure made up of Nodes, but I'm having a problem with my Node.h class as each Node need to have a reference Variable to other Nodes,it's children. which ends up giving ...
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1answer
634 views

Getting RGB values from camera

I have a camera I'm planning on attaching to an arduino uno, that I want to take pictures and extract the average RGB value from each image. This is the camera I have, but I've now realized that it ...
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1answer
115 views

Simple Arduino Serial Arithmetic

I'm developing a program to calculate static margin of an aircraft through the calculations of mass,moment and arm. Essentially dealing with large numbers. I'm having difficulty in setting up my code ...
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1answer
5k views

error: invalid conversion from 'char' to 'char*' [-fpermissive]

I have written a simple code to read data from capacitive keypad and display it on LCD. I am getting the data from keypad in following data structure. char phoneNumber[PHONE_DIGITS]; and then ...
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0answers
86 views

incoming GSM data stored as variable in code [closed]

I am using an Arduino Mega board with a SIM900 GSM. My goal is to be able to text the GSM with a value of two digits (ex: 79) and then store that value as a variable in the code. I know how to set ...
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0answers
339 views

How to get Type name of a variable on Arduino [duplicate]

I found this post and implemented the code in a separate classed and then passed different variables to it in an attempt to get the type name printed to serial. The code compiled and worked fine but ...
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2answers
72 views

How to properly process large arithmetic

just a question that requires a simple answer. How do I process a large number of arithmetic steps in arduino efficiently and precisely? For example I have this code function setup: void calc() { ...
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1answer
231 views

changing analog pins data logging using sdFat library

Background: My goal is to use sdFat library, more precisely AnalogBinLogger example. I want to log data from changing analog pins for example, I want to log from pin 0 to pin 3 for 5 minutes and ...
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5answers
6k views

Serial.print() is slower than it should be

I'm trying to use Arduino as a DAQ but the Serial.print() is not working as fast as I expected. How many bits are sent if you are using a int, because if I use a uint8_t, it's taking the same amount ...