Like the Raspberry Pi single-board computers, the Pico has a total of 40 GPIO pins. GPIO stands for General Purpose Input Output pins. This means that they can be programmed to be used as an input or output. You can tell whether it is a GPIO pin by looking at the label, which should begin with "GP".
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The GPIO pins may also have additional features that are unique to that particular pin. For example the GPIO pins marked GP26-29 are ADC capable.
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You may notice that there may be some "missing" pins. For example, we can't see a GP29 labelled on the Pico.

Not all GPIO pins are available for use, this is because they are already in use! Specifically, there are four I/O pins that are being used by the RP2040 chip on the Pico: GP29, GP25, GP24, and GP23.

From these pins , four internal functions are provided. This includes driving the on-board LED which you will find it labelled as GP25. There is also a pin dedicated to the on-board switched mode power supply (SMPS). Then there are functions for power control and sensing the system voltages.
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There needs to also be a way to power the board. So next up, let's take a look at the 3V3, VSYS, VBUS, AGND, and GND pins.

3V3 - This is the main 3.3V supply to the Pico and it's input and output pins. So in other words, this pin can be used to power parts in your circuit like an LED.

VSYS - This is the main system input voltage. In other words, this pin is directly connected to your Pico's internal power supply. The VSYS pin is used by the on-board SMPS to generate the 3.3V required for the Pico and its GPIO pins. Let's say this was switched off. That would turn off the Pico too! It can vary between 1.8V to 5.5V.

VBUS - This is a source of 5V power taken from the Pico's micro USB port. It can be used to power other hardware which needs more than 3.3V.

AGND - This is a special ground pin or in other words, the ground reference for ADC capable pins (GPIO26-29).

GND - There are several ground pins on the Pico. It is used to complete a circuit that is connected to a power source.
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Breadboards also known as solderless breadboards are one of the most essential components. They are great for making prototypes as they require no soldering. 

If you removed the adhesive backing on the breadboard, you will see horizontal rows of metal strips. These strips are electrically connected. So that means everything in that row of the breadboard are also connected. On some breadboards, there is a dividing line in the middle of the row. 

For example, all holes from A1 to E1 are connected. But F1 to J1 are not. For example, let's say you connected one leg of a LED to E1 and the other leg to F1. That will be fine since it prevents the LED from being shorted.
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Jumper wires are another essential component for prototyping circuits. They can be used to connect the Pico to the breadboard and other components. They come in a few variations including F-F, M-F, and M-M.
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A pushbutton is sometimes known as a momentary switch. Like its name suggests, it is only engaged when it is being pushed. This is different from a typical on/off switch, which latches in its set position.

Let's take a look at the different types of momentary switches. The simplest type is a SPST momentary switch, which stands for single Pole and single Throw. The P stands for Pole, and T here stands for Throw. The number of poles on a switch defines how many separate circuits the switch can control. 

There are other variations including the DPST, and SPDT. For example, an SPST switch has only one pole, so it can only influence one single circuit. On the other hand, a switch like the DPST with two poles can separately control two different circuits.

A switch's throw defines how many positions each of the switch's pole can be connected to. So if a switch has two throws, each pole or separate circuit, can be connected to either of the two terminals.
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A Light-emitting diode or LED, is another commonly used electronic component. It is usually made of epoxy or silicone, is usually translucent and 10mm or smaller in diameter. 

It emits light in response to a small current; This is typically around 20 mA and at a voltage lower than 5VDC. 

They can be used in place of incandescent lamps, and are usually used for illumination or indication purposes. So they're found everywhere from home audio systems, smartphones and watches, battery chargers and many more electronics. 
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The resistor is a fundamental component in electronics. It is a passive component which means it only consumes and not generates power. So what is its purpose? It impedes the flow of current and imposes a voltage reduction. Why is this important?
Here's one example: Without resistors, other components like LEDs will become very hot and burn out.
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Buzzers are noise-creation devices. Inside of them are small metal discs that vibrate against each other when electricity is pulsed through it. This in turn generates a sound! There are two types of buzzers: an active buzzer and a passive buzzer. To start off, we recommend using an active buzzer as these are simpler to use.
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A potentiometer is also known as a variable resistor. You may have already seen one, as they're often found in audio systems as the volume control. It has three terminals and is non polarized, which means that you can connect either of its outer pins to 5V and the opposite pin to GND. 

When two of its three terminals are connected, it become a type of resistor whose resistance can be adjusted by twisting the knob. If all three of its terminals are connected up, it acts a voltage divider.
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A passive infrared (PIR) motion detector is another commonly used component. It monitors movement from sources that emit infrared radiation such as humans and vehicles. They're often found in security alarms since they can reliably detect people.
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An LCD display is also known as liquid-crystal display. It presents information on a small screen and talks to your Pico over a communication protocol called I2C. Through the I2C protocol, the Pico can control the display, sending it everything from alphanumeric characters, symbols, icons, dots or pixels in a bitmap (digital image). 
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A resistor comes in a wide range of values. You can quickly figure out what its value is by looking at its colour code; this is printed as  bands around the resistor body. 

First, make sure you are looking at the right orientation. Position the resistor so that the lone band is to the right. 

Then look at its first band and search for its colour in the 1st band column in the table. Next, look at its second band and look for its colour in the 2nd band column, so on and so forth. So let's say your resistor had these coloured bands: orange, orange, black, black and red. This would mean the resistor's value is 330 ohms with a tolerance of +- 2%. 

What's this about tolerance? It is the percentage of error in the actual value of the resistor. For example, a silver band for tolerance suggests a resistor with a resistance that is 10 percent higher or lower than its rating. A more accurate resistor would be a red band for its tolerance. 

Sometimes, there are also 6 bands on a resistor, the 6th band displays its temperature coefficient denoting its reliability in ppm/K.
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main.py
xxx
Terminal
screen /dev/tty.usbmodem0000000000001 115200
>>> led = Pin(25, Pin.OUT)
>>> from machine import Pin
Breadboard
Breadboard
Mark
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