Questions tagged [arduino-uno]

The Arduino Uno is the most common of the Arduino boards. It is based on the ATmega328P microcontroller.

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97
votes
3answers
100k views

Have I bricked my Arduino Uno? Problems with uploading to board

I can't upload sketches to my Arduino Uno. Have I "bricked" it? What steps can I take to work out what is wrong? What can I do to fix it?
71
votes
9answers
150k views

How can I create multiple running threads?

Is there a way I can have multiple parts of the program running together without doing multiple things in the same code block? One thread waiting for an external device while also blinking a LED in ...
61
votes
1answer
210k views

How do you use SPI on an Arduino?

With reference to the Arduino Uno, Mega2560, Leonardo and similar boards: How does SPI work? How fast is SPI? How do I connect between a master and a slave? How do I make an SPI slave? Please note: ...
58
votes
13answers
65k views

Is there a way to have more than 14 Output pins on arduino?

Is it possible to have more than 14 output pins on the Arduino, I am working on a project in which I need to light up several LEDs individually. I only have an Arduino Uno, and I don't want to get a ...
50
votes
2answers
63k views

What happens if I power the Arduino with both the USB and external power voltage simultaneously?

I am a new Arduino user. I am not sure whether I can connect both USB and external supply through power adaptor to Arduino simultaneously. Would this burn the controller? Basically, I want to ...
46
votes
11answers
10k views

Is an Arduino capable of running 24/7?

I'm making a simple Arduino web server and I want to keep it turned on all the time. So it must endure to stay working continuously. I'm using an Arduino Uno with a Ethernet Shield. It's powered ...
45
votes
11answers
149k views

Mac OSX Yosemite no serial ports showing for Uno R3

I have a MacBook Pro running OS X Yosemite (10.10.3). I connected my Arduino UNO R3 to my computer for the first time after the Yosemite upgrade - it worked fine before this! When I opened the ...
33
votes
2answers
57k views

What are the AREF, IOREF, and the unlabeled pin next to IOREF on the Uno R3?

There are some pins on the Arduino which I haven't been able to find out anything about: IOREF AREF An unlabeled one next to IOREF What are they?
32
votes
12answers
162k views

How can I connect to an Arduino using WiFi?

I'm working on building a solar powered, Arduino based weather station. The weather station consists of a temperature sensor and a photoresistor, and I plan to add an anemometer in the future. I would ...
31
votes
14answers
54k views

Most compact method of powering Arduino from wall socket

There are a lot of methods to power an Arduino from a large range of voltages: USB cable from PC or from a phone charger or an USB hub step down converters step up converters switching power supply ...
30
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2answers
62k views

Arduino as USB HID

Is it possible to build a HID device (like a keyboard) using an Arduino uno? At the time being, I have button inputs on the Arduino giving outputs on the serial line. So, how can I transform my ...
28
votes
7answers
33k views

How can I get a unique ID for all my Arduino boards?

Once you have uploaded a sketch to one of your Arduino boards, it is hard to know exactly what source code led to that sketch. Indeed, you may change the source code of your sketch on your PC without ...
27
votes
2answers
10k views

Arduino USB Power vs External Power Supply

Why is the Arduino able to accept ~5V from the USB, but requires a min of 7V when using an external power supply?
26
votes
3answers
121k views

What is Serial.begin(9600)?

I know that this is to initialize something: Serial.begin(9600); But I want to know what it really means?
22
votes
2answers
27k views

Why do some pins have a different PWM frequency?

According to the Arduino reference for analogWrite(), the PWM frequency on most pins is ~490 Hz. However, it's ~980 Hz for pins 5 and 6 on the Uno, and for pins 3 and 11 on the Leonardo. Why are ...
22
votes
2answers
67k views

Reset an Arduino Uno in code

Is it possible to reset an Arduino (i.e., to reboot it) from code (i.e from the sketch itself)? I know that is possible with a special circuit but is there a chance to make it just with code? Below ...
21
votes
2answers
9k views

Why can't I upload a sketch while other components/devices are connected to my Uno?

I wanted to make a fairly simple circuit which would flash a series of LEDs in sequence, using my Arduino Uno (more specifically, a SainSmart clone). I wrote my sketch and it compiled fine. After that,...
20
votes
2answers
33k views

Is there a limit on how much current a pin can sink?

I've been experimenting with an 8x8 LED matrix controlled by an Arduino Uno. As I think is typical, the matrix uses a common anode for each row, and a common cathode for each column. At the moment, ...
19
votes
2answers
48k views

How many interrupt pins can an Uno handle?

I am looking at using a 7 channel RC receiver with the Arduino Uno R3. In the documentation, there are mentions of a maximum of 2 interrupt pins, whereas on certain other blogs I have seen mentions of ...
19
votes
3answers
23k views

Arduino program only works when run as root

Uploading simple sketches seems to work when I run the Arduino program as root (sudo). I would like to run it as a regular user. Has anyone faced the same problem before and fixed it? Here is what I ...
19
votes
4answers
24k views

Parse JSON with arduino to turn on LED

Hi i'm trying to parse JSON resposne from webserver in my arduino in order to turn on and off a LED light. I'm using the wifi client repeating example to make a get request to my server: http://...
19
votes
3answers
155k views

How to check my Arduino board is working or dead?

When you have a board in your hand but you don't know is it working or not, how to verify if it's working or dead?
19
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2answers
3k views

Does Arduino Uno R3 require cooling in a closure?

I was looking at getting an enclosure to house my Arduino Uno R3, but I'm not sure if I should also attach a fan. Does anyone have experience with this? It doesn't look like much heat is being ...
18
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6answers
19k views

Smaller and cheaper alternative to Arduino Uno for permanent projects

I have played a bit around with a Arduino Uno that came in a kit with a breadboard and components. Soon I would like to make some more permanent things. I would prefer a smaller and cheaper unit than ...
18
votes
2answers
5k views

Should all unused analog input ports be tied to ground for accurate A2D measurements?

I am using the A0 port on my Arduino Uno to read the voltage output from an LM35 temperature sensor. I observed that the reading fluctuates a lot if I leave the remaining analog input ports A1 to A5 ...
18
votes
4answers
25k views

How to get weight data from glass electronic bathroom scale sensors?

I am doing a small project with a bathroom scale but I run into some problems. I am using an Arduino Uno V3, HX711 module amp and a scale. Scale: HX711 amplifier: I disassembled the scale to get ...
17
votes
2answers
25k views

What happens when I call exit() from my program?

In either of setup or loop, if I were to add an exit(0) call, where would control be passed to? What would the next state of the microcontroller be? Would it stop execution and power down? I am using ...
17
votes
1answer
10k views

What's the 2nd ICSP header for in Arduino Uno R3?

Looking at my Arduino Uno R3 board and its reference design schematic I noticed that there's a second ICSP 6-pin header. In the schematic, the connector I'm referring to is named ICSP1. What's that ...
16
votes
7answers
118k views

How do I know the sampling frequency?

I am beginning to get a bit confused about sampling rates and baudrates etc. I have this Arduino code: #include <eHealth.h> extern volatile unsigned long timer0_overflow_count; float fanalog0;...
15
votes
1answer
22k views

How do interrupts work on the Arduino Uno and similar boards?

Please explain how interrupts work on the Arduino Uno and related boards using the ATmega328P processor. Boards such as the: Uno Mini Nano Pro Mini Lilypad In particular please discuss: What to use ...
15
votes
6answers
66k views

How do I erase the memory of the Arduino Uno?

I'm just a tinkerer learning Arduino with my son and I was surprised that when I plugged the USB cord back in to the Arduino the program was still running and I thought to myself, "it's a good thing I ...
15
votes
1answer
8k views

How many times can I upload a program or sketch to my Arduino Uno Clone Board?

I'm about to work on my very first project using arduino (I'm just about to buy one next week), and one of our professor says that we can only upload a program or sketch in an Arduino Uno Board for ...
15
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2answers
12k views

What is the difference between the revisions of the Arduino Uno board?

There are three different revisions of the Arduino Uno. What changed in each revision?
15
votes
2answers
22k views

Controlling Floppy Disk Drive with Arduino

I am having problems controlling a 3.5" Floppy Disk Drive with an Arduino Uno. I have the floppy disk drive powered with a computer power supply that is switched on, and the Arduino powered by my ...
15
votes
4answers
14k views

Is my Arduino dead or is it just its processor?

I have a problem with my Arduino. I can't upload any sketches to it (it gives me the error avrdude: verification error; content mismatch), but the LEDs are still blinking. Do you think that the whole ...
14
votes
1answer
44k views

What is an ICSP pin?

What is an ICSP pin? I have read that it is an AVR and a tiny programming header for the Arduino, but what is an AVR and what does an ICSP pin do?
14
votes
5answers
5k views

How to connect two Arduino without shields?

I'm planning an Arduino system that consists of several Arduino boards. The maximum distance between the boards is about 50 meters. I want to send basic data between these, like short strings or ...
14
votes
2answers
75k views

How do I convert a float into char*?

Asked this question on Electrical Engineering Stack Exchange and was directed here: Pretty self explanatory; how would I go about converting a float into a char*? I have code in which the float '...
14
votes
3answers
35k views

What are the fundemental differences of different Bluetooth modules for beginners?

I'm a beginner to microcontrollers and electronics, albeit not really to computers and programming. Starting out with the Arduino, I came to a point whereby I'm really interested in getting my ...
13
votes
5answers
20k views

Reducing lag between the arduino and a processing sketch on my computer

I'm currently on project #14 of the Arduino project book. I'm trying to control a processing sketch on my laptop using my Arduino. This is accomplished by using a potentiometer to control the ...
13
votes
4answers
33k views

What's the deal with Uno's pin 13 LED?

(I have a Sparkfun RedBoard, but this question seems to apply to R3 Unos and Uno-compatible boards.) As I was building the first circuit in my SIK guidebook (add a resistor, LED, hook it up and make ...
13
votes
4answers
2k views

Some Arduino components seem ridiculously cheap

My project is an Arduino-based device, packed into a box. It will need to use Speed, Latitude, Longitude and Altitude data to log hills it detects on to an SD. On the press of a button, it will need ...
13
votes
1answer
4k views

What happens when code is uploaded using the bootloader?

When I upload a new sketch to my Arduino Uno using the Optiboot bootloader, what really happens? What is sent to the Arduino? How does it respond? What does "not in sync mean"? What is "in sync" ...
13
votes
1answer
1k views

Cannot program two arduinos at the same time because they both use the same COM port

I am not able to program my second arduino because they both use the same com port. In other words this picture says it all: In order to upload my sketch I have to disconnect one arduino. How can I ...
13
votes
2answers
617 views

Installing a different firmware on Arduino

Is it possible to upgrade the firmware on an Arduino so that it can do more things such as change undervolting/ overvolting in order to provide more processing power. To do this you would have to most ...
13
votes
2answers
3k views

Making analog telephone calls?

How can we make the Arduino board interact with old, analog telephone, and to make phone calls? I guess it involves connecting the board to the telephone with some specific cable (how it's called?) ...
13
votes
3answers
658 views

How do I figure out if my board is approaching end of life?

I have a uno that I have been using for 3 years now. I will be using it again in a rather critical project in which failure on the part of the board could be rather expensive and dangerous. So, I ...
12
votes
5answers
4k views

Does an Arduino get worn out by too much command execution?

Excuse me if it is a silly question, but I couldn't find an answer. I've been wondering for a while whether an Arduino (or generally any other micro-controller) gets happy if the code is light and ...
12
votes
6answers
136k views

How do I resolve "avrdude: stk500_recv(): programmer is not responding"?

Whenever I try to program my Arduino UNO Rev.3, I'm seeing the following error avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00 ...
12
votes
6answers
27k views

How to output a true analog voltage at output pin

Regarding my program, it is a program that does some calculations and then outputs a voltage based on the result using analogWrite function. However my problem is that I had done my programming based ...

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