Lesson 00 - Understanding the Raspberry Pi Boards And Accessories

0.1 Raspberry Pi Hardware

Hardware Comparisons

Hardware Comparison

Family	Model	CPU	Memory	Form Factor	Network	GPIO	Power	Released
Raspberry Pi 1	B+	BCM2835 (Single-Core 700MHz)	512MB	Standard (85.60 × 56.5 mm)	100 Base Ethernet	40-Pin		2014
Raspberry Pi 1	A+	BCM2835 (Single-Core 700MHz)	512MB	Compact (65 × 56.5 mm)	None	40-Pin	via μUSB	2014
Raspberry Pi 2	B	BCM2836 / 7	1GB	Standard (85.60 × 56.5 mm)	Yes	40-Pin		2015
Raspberry Pi Zero				Ultra-Compact (65 × 30 mm)				2015
	W / WH	BCM2835 (Single-Core 1 GHz)	512MB RAM	Ultra-Compact (65 × 30 mm)	802.11 b/g/n WiFi Bluetooth 4.1/BLE			2017
	2W	RP3A0 (Arm Cortex-A53 1GHz)	512GB SDRAM	Ultra-Compact (65 × 30 mm)	2.4GHz 802.11 b/g/n WiFi Bluetooth 4.2/BLE		5.1V/2.5A DC via μUSB	2021
Raspberry Pi Pico	Pico	RP2040 Arm Cortex-M0+ (Dual-Core 133MHz)	264KB SRAM	Pico (21 × 51 mm)		40-Pin		2021
Raspberry Pi Pico	Pico W	RP2040 Arm Cortex-M0+ (Dual-Core 133MHz)	264KB SRAM	Pico (21 × 51 mm)	2.4GHz 802.11n WiFi Bluetooth 5.2			2022
Raspberry Pi 3	B	BCM2837 (Quad-Core 1.2GHz)	1GB SDRAM	Standard (85.60 × 56.5 mm)	WiFi Bluetooth BLE	40-Pin	5.1V/2.5A DC via μUSB	2016
	A+	BCM2837B0 (Quad-Core 1.4GHz)	512MB LPSSR2	Compact (65 × 56.5 mm)	Dual-band 802.11ac WiFi Bluetooth 4.3/BLE	40-Pin	5V/2.5A DC via μUSB	2018
	B+	BCM2837B0 Cortex-A53 (1.4 GHz)	1GB LPDDR2	Standard (85.60 × 56.5 mm)	Gigabit Ethernet over USB2 Dual-Band 802.11ac WiFi Bluetooth 4.2/BLE	40-Pin	5V/2.5A DC via μUSB	2018
Raspberry Pi 4	B/A	BCM2711 (Quard-Core 1.8GHz)	1GB / 2GB / 4 GB / 8GB	Standard (85.60 × 56.5 mm)	Gigabit Ethernet Dual-band 802.11ac WiFi Bluetooth 5.0/BLE	40-Pin	5V/3A DC via USB-C	2019: 1GB / 2GB / 4GB 2020: 8GB
Raspberry Pi 4	400	BCM2711 (Quard-Core 1.8GHz)	4 GB	Keyboard (285 × 122 × 23 mm)	Gigabit Ethernet Dual-band 802.11ac WiFi Bluetooth 5.0, BLE	40-Pin	5V/ DC via USB	2020
Raspberry Pi 5		BCM2712 (Quad-Cord 2.4GHz)	4GB 8GB	Standard (85.60 × 56.5 mm)	Gigabit Ethernet Dual-band 802.11ac WiFi	40-Pin	5V/5A DC via USB-C	2023

Pi Pico

Raspberry Pi Pico

There are two versions of Pi Pico W boards:

Raspberry Pi Pico WH with PRE-SOLDERED male headers by Raspberry Pi is breadboard friendly, plug and use!

Raspberry Pi Pico W without header, SMD-friendly

Specification

CPU: RP2040 Dual-core ARM Cortex-M0+ processor, flexible clock running up to 133 MHz
(microcontroller chip designed by Raspberry Pi in the UK)
RAM: 264kB on-chip SRAM
Flash: 2MB onboard Q-SPI flash
Wifi: 2.4GHz 802.11n wireless LAN (Raspberry Pi Pico W and WH only)
Bluetooth: Bluetooth 5.2 (Raspberry Pi Pico W and WH only)
26 multifunction GPIO pins, including 3 analog inputs
2 × UART, 2 × SPI controllers, 2 × I2C controllers, 16 × PWM channels
1 × USB 1.1 controller and PHY, with host and device support
8 × Programmable I/O (PIO) state machines for custom peripheral support
Supported input voltage 1.8 ~ 5.5V DC
Operating temperature -20°C to +85°C (Raspberry Pi Pico and Pico H); -20°C to +70°C (Raspberry Pi Pico W and Pico WH)
The castellated module allows soldering directly to carrier boards (Raspberry Pi Pico and Pico W only)
Drag-and-drop programming using mass storage over USB
Low-power sleep and dormant modes
Accurate on-chip clock
Temperature sensor
Accelerated integer and floating-point libraries on-chip
21 mm × 51 mm form factor

The Raspberry Pi Pico series is a range of tiny, fast, and versatile boards built using RP2040, the flagship microcontroller chip designed by Raspberry Pi in the UK.

Pi Zero

Pi 3

Pi 4

Pi 5

0.2 Pi Board Pinout

Pi Pico Pinout

Pi 3/4/5 Pinout

BCM	wPi	Name	Mode	Pin Header	wPi
		3.3V		1	2	5V
2	8	GPIO 2 / I2C1.SDA	Pull-up Resistor	3	4	5V
3	9	GPIO 3 / I2C1.SCL	Pull-up Resistor	5	6	GND
4	7	GPIO 4 / GPCLK0		7	8	UART.TxD / GPIO 14	15	14
		GND		9	10	UART.RxD / GPIO 15	16	15
17	0	GPIO 17 / SPI1.CE1		11	12	SPI1.CE0 / PCM CLK / GPIO 18	1	18
27	2	GPIO 27		13	14	GND
22	3	GPIO 22		15	16	GPIO 23	4	23
		3.3V		17	18	GPIO 24	5	24
10	12	GPIO 10 / SPI0.MOSI		19	20	GND
9	13	GPIO 9 / SPI0.MISO		21	22	GPIO 25	6	25
11	14	GPIO 11 / SPI0.SCLK		23	24	SPI.CE0 / GPIO 8	10	8
		GND		25	26	SPI.CE1 / GPIO 7	11	7
0	30	GPIO 0 / EEPROM I2C0.SDA		27	28	EEPROM I2C0.SCL / GPIO 1	31	1
5	21	GPIO 5 / GPCLK1		29	30	GND
6	22	GPIO 6 / GPCLK2		31	32	PWM0 / GPIO 12	26	12
13	23	GPIO 13 / PWM 1		33	34	GND
19	24	GPIO19 / PCM FS / SPI1.MISO		35	36	SPI1.CE2 / GPIO 16	27	16
26	25	GPIO 26		37	38	SPI1.MOSI / PCM DIN / GPIO 20	28	20
		GND		39	40	SPI1.SCLK / PCM DOUT / GPIO 21	29	21

5V Power

5V Power

The 5V power pins on the Raspberry Pi board are directly linked to the Pi's power input and can deliver the full supply current of your mains adapter minus the amount used by the Pi itself.

Using a reliable power supply, like the official Pi adapter, you can typically draw about 1.5A. However, this may vary depending on the Pi model and adapter. An external power supply is recommended for high-current devices, such as LED panels, long LED strips, or motors.

3.3 V Power

Ground

I2C

I2C — Inter-Integrated Circuit

GPIO 2 and GPIO 3: These pins on the Raspberry Pi are designated as I2C1 pins, enabling two-wire communication with a variety of external sensors and devices. This makes them essential for interfacing with components that require I2C communication.

Pull-up Resistors: The I2C pins (GPIO 2 and GPIO 3) include fixed 1.8 kΩ pull-up resistors to 3.3V. Due to these built-in pull-ups, these pins are not suitable for general-purpose I/O where the pull-up might interfere with the operation.

Multi-Drop Bus: I2C is a multi-drop bus, meaning that multiple devices can be connected to the same two I2C pins. Each device must have a unique I2C address to communicate properly on the bus.

Verifying I2C Addresses: You can verify the addresses of connected I2C peripherals with the following commands:

sudo apt-get install i2c-tools
sudo i2cdetect -y 1

These commands will scan the I2C bus and display the addresses of any connected devices.

Accessing I2C in Python: To interact with I2C devices in Python, you can use the smbus library. Here's an example of how to write data to a device:

import smbus

DEVICE_BUS = 1
DEVICE_ADDR = 0x15
bus = smbus.SMBus(DEVICE_BUS)
bus.write_byte_data(DEVICE_ADDR, 0x00, 0x01)

GPIO 0 and GPIO 1 (Pin 27 & 28): These pins can be used as an alternate I2C bus (I2C0). However, they are typically reserved by the system for reading the HAT EEPROM, which contains configuration information for add-on boards.

SPI

SPI — Serial Peripheral Interface

SPI0 Pins: The primary SPI bus (SPI0) uses the following GPIO pins:

GPIO 7 (CE1)
GPIO 8 (CE0)
GPIO 9 (MISO)
GPIO 10 (MOSI)
GPIO 11 (SCLK)

SPI1 Pins: The secondary SPI bus (SPI1) uses these GPIO pins:

GPIO 16 (CE2)
GPIO 17 (CE1)
GPIO 18 (CE0)
GPIO 19 (MISO)
GPIO 20 (MOSI)
GPIO 21 (SCLK)

Four-Wire Serial Bus: SPI is known as a four-wire serial bus, consisting of:

MISO (Master In Slave Out)
MOSI (Master Out Slave In)
SCLK (Serial Clock)
CE (Chip Enable/Chip Select)

This setup allows you to attach multiple compatible devices to a single set of pins by assigning each device a different chip-select (CE) pin.

Communication with SPI Devices: To communicate with an SPI device, you assert its corresponding chip-select pin. This selects the device and enables data transfer between the Raspberry Pi and the device.

Default SPI0 Configuration: By default, the Raspberry Pi allows the use of SPI0 with the following chip-select pins:

CE0 on GPIO 8 (Pin 24)
CE1 on GPIO 7 (Pin 26)

Enabling SPI1: To enable the secondary SPI bus (SPI1), configure a device tree overlay in the /boot/config.txt file. For example:

dtoverlay=spi1-3cs

This configuration enables SPI1 with three chip-select lines.

UART

UART — Universal Asynchronous Receiver/Transmitter

UART Pins:

In BCM mode, the UART pins are GPIO 14 (TX) and GPIO 15 (RX).
In WiringPi, the UART pins are designated as GPIO 15 (TX) and GPIO 16 (RX).

Asynchronous Serial Communication: UART is an asynchronous serial communication protocol that transmits data bytes by sending the individual bits sequentially. Unlike synchronous communication, UART does not require a shared clock signal between the sender and receiver. Instead, both ends agree on timing parameters beforehand and use special bits, known as 'start bits', to synchronize the data transmission.

Common Uses: UART is frequently used on the Raspberry Pi for various purposes:

Controlling the Pi over the GPIO.
Accessing kernel boot messages from the serial console (enabled by default).
Interfacing with other microcontrollers or devices such as Arduino, bootloaded ATmega, ESP8266, etc.

Logic Level Considerations: Be cautious about the voltage levels when interfacing the Raspberry Pi with other devices. The Pi operates at 3.3V logic, while devices like the Arduino use 5V logic. Directly connecting these without appropriate level shifting can damage the Pi, potentially releasing the "magic blue smoke."

UART Availability:

Raspberry Pi 2/3: These models have two UARTs, uart0 and uart1.
Raspberry Pi 4: This model includes four additional UARTs. However, only uart0/1 is enabled by default over GPIO pins 14 (TX) and 15 (RX). The additional UARTs can be enabled through device tree overlays in the /boot/config.txt file.

Enabling Additional UARTs:

To enable additional UARTs on the Raspberry Pi 4, you need to modify the /boot/config.txt file with appropriate device tree overlays.

Python Example with WiringPi:

If you have WiringPi-Python installed, you can use the following example to open the Pi's UART at 9600 baud and send the string 'hello world':

import wiringpi

wiringpi.wiringPiSetup()
serial = wiringpi.serialOpen('/dev/ttyAMA0', 9600)
wiringpi.serialPuts(serial, 'hello world!')

This script initializes WiringPi, opens the UART device /dev/ttyAMA0 at 9600 baud, and sends the "hello world!" string through the serial interface.

Understanding and utilizing these detailed descriptions allows you to effectively manage UART communications and connect various devices to your Raspberry Pi.

PWM

PWM — Pulse-Width Modulation

Pulse-Width Modulation (PWM): PWM is a technique used to create an analog-like voltage by rapidly toggling a digital pin on and off. The output voltage is controlled by adjusting the ratio of the time the signal is high (on) to the time it is low (off). This ratio is known as the duty cycle, which is expressed as a percentage.

Applications of PWM:

Controlling LED Brightness: By varying the duty cycle, you can control the brightness of an LED. A higher-duty cycle produces a brighter LED, while a lower-duty cycle dims it.
Motor Speed Control: PWM is commonly used to regulate the speed of DC motors. Adjusting the duty cycle allows precise control over the motor's speed.
Generating Analog Signals: PWM can simulate analog signals for audio applications or other scenarios where a true analog output is required.

PWM Pins on Raspberry Pi:

Hardware PWM: Certain GPIO pins on the Raspberry Pi support hardware PWM, which is handled by dedicated hardware within the Pi, providing more precise control. For example, GPIO 12 and GPIO 13 are capable of hardware PWM.
Software PWM: Any GPIO pin can be used for software PWM, where the PWM signal is generated by the CPU. While this offers flexibility, it may not be as precise as hardware PWM due to CPU timing limitations.

Configuring PWM on Raspberry Pi:

To use PWM on the Raspberry Pi, you can configure the pins using various libraries such as RPi.GPIO for Python or WiringPi for C. Below is an example using RPi.GPIO:

Python Example with RPi.GPIO:


import RPi.GPIO as GPIO
import time

# Set the GPIO mode
GPIO.setmode(GPIO.BCM)

# Set up the PWM pin
PWM_PIN = 18
GPIO.setup(PWM_PIN, GPIO.OUT)

# Initialize PWM on the pin with a frequency of 1 kHz
pwm = GPIO.PWM(PWM_PIN, 1000)

# Start PWM with a duty cycle of 50%
pwm.start(50)
try:
while True:
for duty_cycle in range(0, 101, 5): # Increase duty cycle from 0% to 100%
pwm.ChangeDutyCycle(duty_cycle)
time.sleep(0.1)
for duty_cycle in range(100, -1, -5): # Decrease duty cycle from 100% to 0%
pwm.ChangeDutyCycle(duty_cycle)
time.sleep(0.1)
except KeyboardInterrupt:
pass
# Stop PWM and clean up
pwm.stop()
GPIO.cleanup()

This script sets up GPIO pin 18 for PWM, starts the PWM signal with a 50% duty cycle, and then varies the duty cycle between 0% and 100% in a loop.

PCM

PCM — Pulse-Code Modulation

Pulse-Code Modulation (PCM): PCM is a method used to represent analog signals digitally. It samples the analog signal's amplitude at regular intervals and then quantizes these samples into discrete digital values. This digital representation allows the analog signal to be stored, processed, and transmitted digitally.

PCM on the Raspberry Pi: PCM is used as digital audio output. The PCM interface provides high-quality sound output, which a Digital-to-Analog Converter (DAC) can convert to analog signals.

PCM Pins on Raspberry Pi:

BCM Mode: The primary PCM pins in BCM mode are:
- GPIO 18 (PCM_CLK) - Clock
- GPIO 19 (PCM_FS) - Frame Sync
- GPIO 20 (PCM_DIN) - Data In
- GPIO 21 (PCM_DOUT) - Data Out

Applications of PCM:

High-Quality Audio Output: PCM is commonly used to output high-quality digital audio from the Raspberry Pi to external DACs, amplifiers, or audio devices.
Digital Audio Interfacing: It connects digital audio equipment and is often used in professional audio and home theater systems.

Configuring PCM on Raspberry Pi:

To use the PCM interface on the Raspberry Pi, you may need to configure your system settings and ensure that the appropriate GPIO pins are enabled for PCM functionality. This can involve editing the /boot/config.txt file to enable the PCM interface.

Example Configuration in /boot/config.txt:

dtoverlay=pcm

This overlay ensures the PCM functionality is enabled on the specified GPIO pins.

Using PCM for High-Quality Sound:

You can achieve high-fidelity sound output from your Raspberry Pi by connecting a DAC to the PCM pins. This setup is ideal for audio projects that require precise and high-quality audio playback.

Practical Example:

When using PCM for audio output, ensure that your external DAC is compatible with the PCM signal format and is properly connected to the PCM pins on the Raspberry Pi.

GPCLK

GPCLK — General Purpose Clock

General Purpose Clock (GPCLK): GPCLK pins on the Raspberry Pi can be configured to output a fixed frequency without requiring ongoing software control. This makes them useful for applications that need a stable and precise clock signal.

Available Clock Sources:

The following clock sources are available for GPCLK pins:

0: 0 Hz (Ground)
1: 19.2 MHz oscillator
2: 0 Hz (testdebug0)
3: 0 Hz (testdebug1)
4: 0 Hz (PLLA)
5: 1000 MHz (PLLC - changes with overclock settings)
6: 500 MHz (PLLD)
7: 216 MHz (HDMI auxiliary)
8-15: 0 Hz (Ground)

Clock Divider: Other frequencies can be achieved by setting a clock divider, which is calculated using the formula:

\(Frequency = {{SOURCE} \over {DIV\_I + {{DIV\_F} \over {4096}}}}\)

Note that the BCM2835 ARM Peripherals document contains an error and incorrectly states that the denominator of the divider is 1024 instead of 4096.

GPCLK Pins on Raspberry Pi:

BCM Mode: The primary GPCLK pins in BCM mode are:
- GPIO 4 (GPCLK0)
- GPIO 5 (GPCLK1)
- GPIO 6 (GPCLK2)

Applications of GPCLK:

Clock Signals for Peripherals: GPCLK can provide clock signals to peripherals and other hardware components that require a stable frequency.
Timing and Synchronization: It is useful for applications requiring precise timing and synchronization, such as communication protocols and data acquisition systems.

Configuring GPCLK on Raspberry Pi:

To configure the GPCLK pins, you can use the gpio utility or other software libraries that allow low-level hardware control.

Example Configuration:

Using the gpio utility in a Linux environment, you can set up a GPCLK pin with a specific frequency. For example:

gpio -g mode 4 ALT0
gpio -g clock 4 19200000

This command configures GPIO 4 to ALT0 mode (GPCLK0) to output a 19.2 MHz clock signal.

1-Wire

1 Wire — One-Wire Interface

One-Wire Communication Bus: The One-Wire (1-Wire) interface is a single-wire communication bus typically used to connect sensors and other devices to the Raspberry Pi. It allows for data exchange between the Pi and connected devices over a single data line, simplifying the wiring.

Default and Custom GPIO Pins: While the Raspberry Pi supports the One-Wire interface on any GPIO pin, the default pin is GPIO 4. You can also configure it to use a custom GPIO pin if needed.

Enabling One-Wire Interface:

To enable the One-Wire interface, add the following line to /boot/config.txt and then reboot your Raspberry Pi:

dtoverlay=w1-gpio

For a custom GPIO pin, use:

dtoverlay=w1-gpio,gpiopin=<pin_number>

Replace <pin_number> with the desired GPIO PIN.

Enabling One-Wire via Command Line:

Alternatively, you can enable the One-Wire interface on demand using raspi-config or the following command:

sudo modprobe w1-gpio

Dynamic Overlay Loading:

With newer kernels (4.9.28 and later), you can use dynamic overlay loading to create multiple One-Wire buses simultaneously:

sudo dtoverlay w1-gpio gpiopin=4 pullup=0 # GPIO 4 (header pin 7)
sudo dtoverlay w1-gpio gpiopin=17 pullup=0 # GPIO 17 (header pin 11)
sudo dtoverlay w1-gpio gpiopin=27 pullup=0 # GPIO 27 (header pin 13)

These commands configure the specified GPIO pins for One-Wire communication without enabling the internal pull-up resistor.

Listing Discovered Devices:

Once the One-Wire interface is enabled and device discovery is complete, you can list the devices discovered by the Raspberry Pi on all One-Wire buses (default is GPIO 4) using:

ls /sys/bus/w1/devices/

Pull-Up Resistor Requirement:

When using the One-Wire interface on the Raspberry Pi, a 4.7 kΩ pull-up resistor is typically required. This resistor should connect the GPIO pin and the 3.3V supply (e.g., header pin 1 or 17).

Alternative Connection Methods:

Other methods for connecting One-Wire devices to the Raspberry Pi include using I2C to One-Wire bridge chips, which can facilitate communication between the Pi and One-Wire devices via the I2C bus.

Lesson 00 - Understanding the Raspberry Pi Boards And Accessories

0.1 Raspberry Pi Hardware

Hardware Comparisons

Pi Pico

Pi Zero

Pi 3

Pi 4

Pi 5

0.2 Pi Board Pinout

Pi Pico Pinout

Pi 3/4/5 Pinout

5V Power

3.3 V Power

Ground

I2C

SPI

UART

PWM

PCM

GPCLK

1-Wire

1.3 Power Modules for Pi Boards

Waveshare UPS Module, 3S 5V/5A

Geekworm X1202 UPS 5.1V/5A HAT for Pi 5

Geekworm X-UPS1 12V/5V/3A Dual Output Universal SBC Stackable UPS Shield

1.4 HAT Boards for Pi 5

Geekworm X1001 PCIe to M.2 Key-M NVMe Adapter

Geekworm X1004 PCIe to Dual 2280 NVMe Shield for Pi 5

GeeekPi Dual FPC PCIe HAT

GeeekPi Quad FPC PCIe HAT

Coral M.2 Accelerator with Dual Edge TPU