How to Read Voltage From Digital Pin on Arduino
The Arduino Uno board has over twenty pins that y'all can utilize for many dissimilar applications. In this mail service I'll give you a complete and practical overview of the main Arduino Uno pins.
If you're starting with Arduino, or if yous're already a software developer and desire to learn more than about the bridge betwixt software and hardware on an Arduino board, and then you've come up to the correct place!
In this post y'all'll see :
- What are the pins you lot can use
- What you tin do with them
- And some tips on how to connect other devices to your Arduino pins
I'll also give you some examples of sensors/actuators that yous can use with each pin functionality.
This post is focused on Arduino Uno lath, merely well-nigh of the explanations (except for the pin numbers on the circuit board) are too valid for any other Arduino lath.
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Arduino Uno pin diagram
Here's a global visual description of all the pins you can find on an Arduino Uno board.
You lot may find that quite difficult to understand at get-go. And then, let'south suspension down each kind of pin, i by 1.
Ground pins
If in that location is one thing, and only one affair that you should remember with the ground, it's: always connect all grounds of your circuits together, and brand sure all components are correctly linked to the ground. Footing pins are often represented past GND on schematics.
The ground is essential for the Arduino board to measure and prepare any voltage. Basically a voltage is a deviation of potential between 2 points: here you take the basis and some other point.
So, if everything in your circuit is continued to the same ground, all the voltages tin can be compared and their value is relevant. If you don't take a mutual basis, then what does 3.3V mean ? Is is greater than a 5V value you measured from another point of your excursion ?
Information technology'due south similar measuring the summit difference between 2 persons: if 1 of them is standing on a box, and then the footing reference is not the aforementioned. And you can't get a valuable measurement if yous don't place the 2 persons on the same level.
Well, I won't go into more details, only you encounter the point.
Arduino Power pins
Power goes 2 ways:
- Yous have to power your Arduino Uno lath from an external source
- You can too power some components plugged to your board
Powering the Arduino Uno lath
For powering the Arduino Uno board, yous have different options. The starting time ane is simply to connect your Arduino board to your calculator using a USB cable – usually yous get i when y'all social club an Arduino board.
You can also use the DC power jack to power your Arduino board with 7-12V. If you lot are using some hobby servomotors powered past your Arduino, you lot might want to use the DC power jack. The power coming from the USB cable is lower. It's great for advice between your lath and your computer (or other Arduino boards), but might be not plenty to power some real motors.
So, you've already got 2 means to power your Arduino Uno lath. At present, if you expect at the ability pins on the circuit, you'll encounter a Vin pin.
You can use this pin to provide 7-12V to your board. Very applied when you demand to use an external ability source and connect it straight to your board. And, equally you can guess, if you use the Vin, y'all likewise demand to use the ground correctly, past connecting information technology to the ground of the external power source.
Note that the USB and DC ability jack already have the footing integrated and which connects to anything you plug on them. In fact, the metal office that you lot can bear upon around the USB connector is directly linked to the ground!
Powering components from the Arduino Uno power pins
As you can guess, whenever yous connect an external component to your Arduino Uno lath, you need to connect information technology showtime to the ground.
And so y'all tin utilize several different pins to power information technology on. Amidst them are the 3.3V and 5V ability pins.
Note – this is important – that the Arduino Uno is operating nether 5V. So, for every output pivot that nosotros'll meet in the following of this mail, be certain to remember that. If you plug a 3.3V component to a 5V ability source, y'all might damage the component.
At that place are 2 alternatives to that: employ the three.3V power source from the Arduino (integrated voltage bridge), or apply 5V with a voltage level shifter. You can easily connect a three.3V to a 5V component, provided that you transform the voltage between them, using resistors or directly a level shifter component.
Arduino Digital pins
Y'all can discover xiv digital pins on an Arduino Uno lath. They are easily recognizable, from 0 to 13 on the circuit board.
Reading/Writing on digital pins
You'll utilise digital pins to read information from some components (sensors) and write information to other components (actuators).
A digital pivot tin can take only two states: LOW or HIGH. Y'all can consider them equally binary pins.
Low ways that the voltage on the pivot is 0V. Loftier means Vcc, which is 5V here for Arduino Uno.
Before you can actually use a digital pin, yous need to configure its mode. A digital pin can either be on INPUT more or OUTPUT way. When in INPUT mode, you'll apply information technology to read information. When in OUTPUT mode, you'll utilise it to write data.
Later on y'all've set a mode for the pin – usually in the setup() function of your Arduino program with pinMode() – you'll be able to read/write the land of the pin with digitalRead()/digitalWrite().
If you accept set the pin to INPUT manner, so y'all can read its state, which will be either HIGH or LOW.
When reading, any voltage applied to the pin lower than 0.8V will be considered as Low, and any voltage greater than 2V will be considered as High. Thus, I stress over again that you lot should correctly connect all the grounds in your excursion together, or else the Arduino Uno won't exist able to read a valuable information! If you don't become reliable and stable data, e'er first bank check about the ground, it'southward very likely that the problem is coming from there.
For examples of how to use digital pins to control a component, check out this Arduino LED tutorial.
For how to employ digital pins to read data from a sensor, check out this Arduino push button button tutorial.
And if you want to become to a more advanced level with digital pins, check out how to make digitalWrite() faster.
PWM
Some of the digital pins can exist used to write a PWM.
A PWM (Pulse Width Modulation) is basically a way to get a specific voltage (ex: 4.1V) with simply HIGH/LOW (5V/0V) states. The PWM creates a pulse running at a given frequency – 500Hz for Arduino Uno. Then, a duty cycle parameter will tell what percentage of each pulse is in the High land or LOW land.
The frequent change of HIGH/LOW states produces an boilerplate voltage output. For example, at a 50% duty bicycle (l% of the fourth dimension Loftier, 50% of the time Low), the output voltage would exist two.5V.
Of class, this explanation is really simplified, but that'southward all you demand to know to get started with the Arduino PWM.
Now, y'all can use the PWM only on some digital pins, which have a "~" adjacent to their number. The Arduino Uno pins compatible with PWM are the pins 3, 5, six, nine, x and 11. Then you have half dozen pins where you tin can create a PWM, using the analogWrite() office.
This can be quite useful to control some actuators that require a fine voltage tuning, and are not only switched on or off.
If we take the case of a LED, you tin use the analogWrite() function to alter the brightness of the LED.
Interrupt pins
And… At that place is another available functionality for the digital pins! Yous tin can use some of them as interrupt pins in your Arduino program.
For Arduino Uno, the choice for those pins is quite express. Only digital pins two and 3 tin can exist used as interrupt pins.
So, how is it working ?
When you create an Arduino programme, you have to know that your lawmaking is running line by line, with no possible multithreading.
Let'due south say you connect a push button push to an interrupt pivot (and to the ground!). In your Arduino program, you can adhere a specific function to be triggered whenever you printing the button. And so, instead of having to continuously read the button state, you can direct utilize the interrupt behavior to launch your function. Think of it equally a push notification, just like on your phone. It tells you lot when there is new content, or a specific action to do. Learn how to use Arduino Interrupts in your code.
Notwithstanding, this doesn't mean that yous have solved the multithreading issue. When the execution of the plan switches to your part called by an interrupt, it will also end the execution of the electric current program and come up back to it only later on the interrupt function has finished.
If you want to learn more than about how to multitask with Arduino, check out this complete tutorial on this field of study.
Arduino Analog pins
You lot can find 6 analog pins on an Arduino Uno board. You lot'll find them well-nigh the ability pins, and they're easily recognizable, from A0 to A5.
Read a value from an analog pin
An analog pin is useful to read values that can't be merely 0 or 1. Allow's say y'all accept a potentiometer and want to get the percentage of the potentiometer value. With a digital pivot you could know when the potentiometer is at minimum and maximum position, but nothing else. With analog pins, you take all the values in between.
Note that the analog functionality on those pins is simply for reading. Normally they are even called "Analog input pins". You can't write an analog value through those pins, don't forget that!
And so, how is an analog input pin working ?
First, it will receive an input voltage and read this voltage. Allow's say the pin reads 2.5V. Then, an ADC (Analog Digital Converter) will change that analog value into something your Arduino program tin can understand – a digital value.
The Arduino Uno board has a x bits ADC. The resolution can be different if you use other Arduino boards. And so, what does 10 bits mean ? Merely that the resolution is 2^10 = 1024. Thus, the value you go when you read data from an analog input pin is betwixt 0 and 1024.
Coming back to our 2.5V example: ii.5V is 50% of 5V (Vcc). In your Arduino program, you volition then get the value 512. From this value, you can easily opposite the computation and get the information about the voltage that was applied.
Too – and it can be quite disruptive at first – remember that the analogWrite() part for PWM is only bachelor for some of the digital pins, and not for analog pins at all.
Using an analog pin equally a digital pivot
Even if you can simply read from an analog pin, you can as well choose to apply it equally a "elementary" digital pivot. (but the opposite is non true)
If the pin tin read whatever value between 0 and 5V, then it will be able to read merely values beneath 0.8V (LOW) and values higher up 2V (HIGH).
To utilize an analog pivot as a digital pin, y'all simply accept to set the mode for the pin, every bit you would exercise for digital pins in the setup() function of your Arduino program. Then, you can use the digitalWrite() and digitalRead() functions and it will work perfectly.
Communication protocols through Arduino pins
Hither is where things showtime to get interesting. Communication protocols over Arduino Uno pins will allow you to employ more advanced sensors and actuators. You'll create more complex and useful applications.
There are 3 main communication protocols you can use with an Arduino Uno board, through the pins of the excursion: UART, I2C, and SPI.
Simply… Nothing is displayed on the excursion!
Don't panic, the communication protocols are using the existing pins on the excursion.
In fact, most of the pins are configurable to use alternate functions, sometimes up to 4 alternate functions for just one pin. Just let's go along things elementary here.
Pins for UART – Serial
UART is the well-nigh used protocol for Arduino – at least when you begin.
When you connect your Arduino Uno board to your reckoner, and communicate via the Serial library, well… You lot are using UART!
You can likewise notice the 2 required pins for UART direct on the Arduino Uno board, on pins 0 and 1: RX and TX. R stands for "reception" and T for "transmission". This is a bidirectional communication.
Note that the Serial used past USB is the same as the ane used with pins 0 and one. And so, if y'all desire to connect some other device to the RX/TX pins of your board, call up not to utilize the Serial through USB.
In some other Arduino boards, like Mega, at that place are several unlike available UARTs. But for Arduino Uno, you only take one.
If however, you lot want to utilise more UARTs, you can always exercise that with the SoftwareSerial library. This library allows you to apply whatever other digital pins for UART purpose. Although there is a big difference hither: "truthful" Serial uses hardware functionality of the Arduino Uno lath, which is very fast and doesn't consume much computation ability. The SoftwareSerial is the reverse: it compensates for hardware with computation ability. Then, start with the standard hardware UART first, and then you'll run across if you need more serial ports for your awarding (in this example I recommend y'all switch to an Arduino Mega to get many hardware UARTs).
To connect a component to the Arduino Uno pins and apply Serial communication, you'll need four cables:
- One betwixt the RX of the component and the TX of the Arduino
- One between the TX of the component and the RX of the Arduino
- If the component is not powered externally, one cable to power it from the ability pins of the Arduino
- And… One for connecting the footing
If y'all're interested in communicating betwixt a Raspberry Pi board and an Arduino board via Series, check out this Raspberry Pi Arduino Serial tutorial.
Pins for I2C
I2C is a bus protocol, with a multi-master/multi-slave architecture. Merely to continue things simple – and most of your applications will only need that – let'south only talk about the one-master/multi-slave part of the architecture.
Basically, imagine a bus of data where all the information goes through. The head of the bus is the master. Now, you lot can add whatsoever new component to the bus, configured as a slave. Likewise, each component has its own ID.
The master device will send data and requests to a slave device, by communication on the bus and providing the ID of the slave. If the master needs a response, the slave will send back the response to the motorbus. In one case the primary has received a response, it can send the next instruction/request.
Commonly, you'll apply your Arduino Uno board as the master, and you lot'll connect one or several components (ordinarily sensors) to the I2C bus, with each a unlike ID. On the software side, you'll use the open up source Arduino Wire library.
Merely, to which Arduino Uno pins should you connect all those components ?
For I2C you can't see any indication straight on the excursion board.
You lot'll need iv cables to apply an I2C bus:
- One to connect the SCL pin (clock)
- Another one for the SDA pivot (data)
- One to power on the components on the bus
- And one to make the common basis
Some examples of I2C compatible components:
- MPL3115A2 temperature sensor
- MPU6050 gyroscope + accelerometer sensor
- TCS34725 color sensor
Pins for SPI
SPI is another protocol based on a principal-slaves architecture.
Yous can utilize it to connect your Arduino board to multiple devices. Note that the communication speed is faster than for I2C and UART, just it's not suitable for mid-long distance advice (more than than a few centimeters for the cable). As for the other communication protocols, yous can direct employ the open up source SPI library on your Arduino programs.
When you're using an SPI device and want to connect it to some pins on your Arduino board, hither are the pins you need to use:
The cable organization for connecting devices with SPI pins is a little fleck more than complex. You need 6 cables minimum:
- SCK pin (clock)
- MISO pivot (Master In, Slave Out)
- MOSI pivot (Chief Out, Slave In)
- One for each CS/SS (Chip Select/Slave Select). For each boosted slave, y'all'll need to add i more connexion to an Arduino pin.
- 1 for powering the components
- And ane for the common footing
Some examples of SPI compatible devices:
- AS5047D magnetic position sensor
- MAX31855 thermocouple-to-digital sensor
Become started with Arduino Uno pins
As you saw in this post, you have a huge number of options when it comes to using Arduino Uno pins.
If you just begin with Arduino, try first to use the digital and analog basic functionalities.
So, you can start to become further with interrupts, PWM outputs, etc.
And finally, at that place's an space number of sensors/actuators y'all tin can connect to your Arduino Uno board to create your next project!
You tin besides connect several Arduino boards together, or even a Raspberry Pi board.
Well, now that yous have a better understanding of Arduino Uno pins, time to go your hands dirty!
If you don't take an idea of what to do with all those pins, cheque out the unlike devices I introduced as examples in this post, this might exist a skilful way to showtime and go more ideas.
Source: https://roboticsbackend.com/arduino-uno-pins-a-complete-practical-guide/
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