Raspberry Pi 3 Model A+: A Compact Powerhouse for Makers
The Raspberry Pi 3 Model A+ offers a compelling blend of performance and compact size, ideal for embedded projects where space is a constraint.
The Raspberry Pi 3 Model A+ is a single-board computer (SBC) that sits within the Raspberry Pi family, released in November 2018. It represents a more compact and cost-effective iteration of the popular Raspberry Pi 3 Model B+, sharing much of its core processing power but in a smaller form factor with fewer onboard peripherals. This makes it an excellent choice for projects where space is at a premium, such as portable devices, robotics, or custom embedded systems.
At its heart, the Raspberry Pi 3 Model A+ features the Broadcom BCM2837B0 System on a Chip (SoC). This 64-bit quad-core ARM Cortex-A53 processor, clocked at 1.4GHz, provides ample computational power for a wide range of applications. While it lacks the Gigabit Ethernet port and the extensive USB connectivity of its larger sibling, the Model B+, it retains the essential features like Wi-Fi and Bluetooth, making it a versatile standalone computing platform.
Compared to earlier 'A' models, the 3 A+ significantly boosts performance with its upgraded CPU and the inclusion of dual-band 802.11ac Wi-Fi and Bluetooth 4.2/BLE. It also features 512MB of LPDDR2 SDRAM, which is sufficient for many embedded tasks and light desktop use. This board is particularly well-suited for makers, students, and embedded engineers who need a capable Linux-based computer in a small footprint, without the need for extensive wired networking or multiple USB peripherals.
The history of the 'A' models in the Raspberry Pi lineage has always been about offering a more affordable and compact option. The 3 Model A+ continues this tradition, providing a powerful yet economical entry point for those who don't require all the features of the larger 'B' models. Its reduced component count also means lower power consumption, further enhancing its appeal for battery-powered or thermally sensitive applications.
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Specifications
| Microcontroller / SoC | Broadcom BCM2837B0 |
| Architecture | 64-bit ARM Cortex-A53 (Quad-Core) |
| Clock speed | 1.4GHz |
| Flash / Storage | MicroSD card slot (up to 32GB recommended, higher possible) |
| RAM / SRAM | 512MB LPDDR2 SDRAM |
| Operating voltage | 3.3V (for I/O), 5V (for power input) |
| Digital I/O pins | 27 (GPIO) |
| Analog / ADC | — |
| PWM | Yes (via GPIO pins, software-controlled) |
| Connectivity | 2.4GHz and 5GHz IEEE 802.11.b/g/n/ac wireless LAN, Bluetooth 4.2, BLE |
| USB | 1x USB 2.0 Type-A port |
| Power input | Micro USB (5V, 2.5A recommended) |
| Dimensions | 65mm x 56.5mm |
Pinout & pin functions
| Pin | Function |
|---|---|
| 3.3V Power | 3.3V Power Output |
| 5V Power | 5V Power Output |
| GND | Ground |
| GPIO 2 | SDA (I2C Data) |
| GPIO 3 | SCL (I2C Clock) |
| GPIO 4 | General Purpose I/O |
| GPIO 17 | General Purpose I/O |
| GPIO 27 | General Purpose I/O |
| GPIO 22 | General Purpose I/O |
| GPIO 10 | SPI MOSI (Master Out Slave In) |
| GPIO 9 | SPI MISO (Master In Slave Out) |
| GPIO 11 | SPI SCK (Serial Clock) |
| GPIO 5 | General Purpose I/O |
| GPIO 6 | General Purpose I/O |
| GPIO 13 | General Purpose I/O (PWM capable) |
| GPIO 19 | General Purpose I/O (PWM capable) |
| GPIO 26 | General Purpose I/O (PWM capable) |
| GPIO 7 | SPI CE0 (Chip Enable 0) |
| GPIO 8 | SPI CE1 (Chip Enable 1) |
| GPIO 25 | General Purpose I/O |
| GPIO 24 | General Purpose I/O |
| GPIO 23 | General Purpose I/O |
| GPIO 18 | General Purpose I/O (PWM capable) |
| GPIO 15 | General Purpose I/O (PWM capable) |
| GPIO 14 | UART TXD (Transmit Data) |
| GPIO 12 | General Purpose I/O (PWM capable) |
| GPIO 16 | General Purpose I/O (PWM capable) |
| GPIO 20 | General Purpose I/O |
| GPIO 21 | General Purpose I/O |
| GPIO 28 | I2C (Alternative) |
| GPIO 29 | I2C (Alternative) |
| GPIO 30 | I2C (Alternative) |
| GPIO 31 | I2C (Alternative) |
| GND | Ground |
| RUN | System Reset (Active low) |
Wiring & circuit basics
Powering the Raspberry Pi 3 Model A+ requires a stable 5V supply, typically delivered through its Micro USB port. A high-quality power supply capable of delivering at least 2.5A is recommended to ensure reliable operation, especially when peripherals are connected or the CPU is under load. The board has onboard voltage regulators to step down the 5V input to the 3.3V required by the SoC and most peripherals. It is crucial to use a dedicated power supply and avoid powering the Pi through its USB data port, as this can lead to instability and damage.
All GPIO pins on the Raspberry Pi 3 Model A+ operate at 3.3V logic levels. Connecting a 5V device directly to a GPIO pin can permanently damage the Raspberry Pi. If you need to interface with 5V logic devices, use a level shifter. For example, to safely connect an LED, you would connect a GPIO pin to one end of a resistor (e.g., 330 Ohm), the other end of the resistor to the LED's anode (longer leg), and the LED's cathode (shorter leg) to a Ground (GND) pin. This limits the current flowing through the LED and protects the GPIO pin.
When connecting sensors, such as an I2C sensor like a BME280, you will need to connect its VCC to a 3.3V pin on the Raspberry Pi, its GND to a GND pin, its SDA pin to GPIO 2 (SDA), and its SCL pin to GPIO 3 (SCL). The Raspberry Pi 3 Model A+ does not have onboard Analog-to-Digital Converters (ADCs), so if you need to read analog sensors, you will require an external ADC module, which can also be interfaced via I2C or SPI.
Programming & getting started
The Raspberry Pi 3 Model A+ runs a full Linux operating system, typically Raspberry Pi OS (formerly Raspbian). This allows for a wide range of programming languages and development environments. For Python development, the default Python interpreter is readily available, and libraries like RPi.GPIO or gpiozero make controlling the GPIO pins straightforward. You can install and use IDEs like Thonny directly on the Raspberry Pi OS.
For more advanced embedded development or cross-compilation, you can use tools like PlatformIO within Visual Studio Code, or even utilize C/C++ with libraries like wiringPi (though less actively maintained now) or pigpio. To get started, flash Raspberry Pi OS onto a MicroSD card using a tool like Raspberry Pi Imager. Insert the card into the Pi, connect a monitor, keyboard, and mouse, and power it up. Once booted, you can open a terminal and start writing Python scripts or install other development tools.