The following are the important features:

• Power:
  • Raspberry Pi is powered by a +5.0V micro USB supply
  • A 2.5 ampere power supply works well to power Pi and it uses a maximum of 1 amp
  • GPIO pins can draw 50 mA of current in total, distributed across all pins where each pin can draw 16 mA
  • The HDMI port uses a 50 mA current, whereas the camera module draws a 250 mA current
  • A USB-based mouse and keyboard can use 100 mA to 1000 mA current

• USB:
  • Raspberry Pi 3 Model B is equipped with four USB 2.0 ports. These are connected to the LAN9512 combo hub/Ethernet chip IC3.
  • USB ports enable the attachment of peripherals such as keyboard, mouse, web camera, and other such USB-based devices.
  • It is an On-the-Go (OTG) USB. The OTG feature allows Pi to work as a host and device interchangeably.
  • Pi has only one root USB bus port. Traffic from all four USB ports is funneled down to this bus, which operates at a max speed of 480 Mbps.

• GPIO:
  • General Purpose Input/Output (GPIO) are a total of 40 pins.
  • Raspberry Pi has a 26-pin header, which can be used as input and output.
  • All 26 pins can receive and transmit data only in digital format.
  • I/O pins range from GPIO02 to GPIO27. Refer to Figure 2.2.
  • There are two pins each for 3.3v DC (pin 01 and pin 17) and 5v DC (pin 02 and pin 04). These pins are used as the power source for the sensor, LEDs, and other such actuators interfaced with Raspberry Pi.
  • There are seven pins assigned as Ground, namely pins 06, 09, 14, 20, 25, 30, and 39, as shown in the following diagram:

• • GPIO pins can be configured to provide alternate functions such as SPI, PWM, I²C, and UART, which we will cover shortly.

• I²C: Since Raspberry Pi has a limited number of GPIOs, we might need more I/O pins in the case of measuring systems. To overcome this, I/O expander chips are used and interfaced with the I²C pins/bus of Raspberry Pi. I²C allows multiple devices to connect to the same bus. Refer to Figure 2.3. Two dedicated pins are provided in Pi GPIO02 and GPIO03 (refer to Figure 2.2). GPIO02 is an SDA, which is the data line, and GPIO03 is SCL, which is a signal used to synchronize all data transfers via the I²C bus:

UART stands for Universal Asynchronous Receiver/Transmitter. It is an asynchronous serial communication protocol, which receives the data in bytes and transmits the individual bits in a sequential manner. Due to its asynchronous nature, it allows users to send data without clock signals; instead, start and end bits are used to synchronize the data transfer. Two pins are defined in Pi for UART communication, GPIO14 (TXD) for transmitting data and GPIO15 (RXD) for receiving data. UART is used to interface devices such as Arduino and ESP8266, and also to get access to kernel boot messages from the serial console.

SPI stands for Serial Peripheral Interface. It is a communication protocol used to transfer data between Raspberry Pi and peripheral devices connected to it, such as sensors and actuators. Let's understand with an example how SPI communicates with analog to digital converters.

SPI uses four dedicated pins for communication. These are marked as Serial Clock (CLK, GPIO011), Master Input Slave Output (MISO, GPIO09), Master Output Slave Input (MOSI, GPIO10), and Chip Select (CS, GPIO08 ,GPIO07).

The clock pin reads the input signal at regular frequency, which is the rate at which data transfer takes place between Pi and ADC.

MISO is the data pin used by the master (Raspberry Pi) to receive data from the slave (ADC).

MOSI is used by the master to send data to the slave.

When multiple peripherals are connected to the same SPI bus chip, selective pins are used to make one peripheral active at a time and to transfer data and ignore the rest of the devices.

PWM stands for Pulse Width Modulation. It is a technique for controlling outgoing power to connected peripherals. For example, we can control the speed of the DC motor using PWM. There are two PWM channels available in Raspberry Pi, GPIO12 and GPIO19.

The following are the different ports for Raspberry Pi 3 Model B:

• Audio/video port: It has a 3.5 mm 4-pole composite audio and video port. This single port carries both audio and video signals. It is a Tip Ring Ring Sleeve (TRRS) type connector.
• HDMI port: It has a full-size HDMI port. Any monitor/TV can be connected to Pi directly.
• The 10/100 BaseT Ethernet port in Pi is used to connect to the internet through a cable. It has the capability of transmitting data at 10 and 100 Mbps.
• CSI Camera port: It also has a Mobile Industry Processor Interface (MIPI) camera serial interface. It facilitates connection to small camera modules directly on board.
• DSI Display Port: It is a high-speed serial interface. It has a very low voltage swing of up to 200mV only, which helps to curb electromagnet noise and consume less power.
• Wi-Fi and Bluetooth: It also includes Broadcom BCM43438 Wi-Fi and a Bluetooth combo chip. Both are implemented on the same chip as completely independent capabilities. The Wi-Fi adaptor is 802.11b/g standard and has a data transfer speed of up to 72.2 Mbps. The same chip has Bluetooth 4.1 and Bluetooth Low Energy.
• Memory card slot: A push-pull micro SD card slot for a memory card is included. Since Pi doesn't have any onboard storage/flash, the OS is installed on a micro SD card and is used for other storage purposes.

All of the previous descriptions should have given you a fair bit of knowledge about your Raspberry Pi hardware, technical specifications, functionalities, and other capabilities.