Embedded Beginner's Guide: Distinguish Chips from Development Boards in 5 Minutes, Starting with Ras
Learn to read chip specs in 5 min: RP2040 vs Pico, explained in plain English for beginners.
COMPONENTS
PROJECT DESCRIPTION
1. Introduction to Raspberry Pi Pico
The Raspberry Pi Pico is a low-cost, high-performance microcontroller development board officially designed by Raspberry Pi, featuring flexible digital interfaces. In terms of hardware, it adopts the RP2040 microcontroller chip independently developed by the Raspberry Pi official, is equipped with an ARM Cortex-M0+ dual-core processor with a running frequency of up to 133MHz, has built-in 264KB SRAM and 2MB of memory, and also comes with as many as 26 multifunctional GPIO pins on board.In terms of software, you can choose the C/C++ SDK provided by Raspberry Pi or use MicroPython for development. It is also equipped with complete development materials and tutorials, which facilitates quick entry into development and embedding applications into products.
2. Hardware Circuit of Pico Development Board
Beginners can think of the RP2040 chip as "a smartphone motherboard without a screen, battery or buttons" — it has core functions but cannot work without these accessories. These hardware circuits supplement the chip with essential functions such as "power supply, clock generator, status indicator and interfaces", turning the Pico from a "bare chip" into a "directly usable development board".
The Raspberry Pi Pico is equipped with some peripheral circuits of the RP2040 chip, including: an external Flash memory chip (W25Q16JV), a clock crystal oscillator, passive components such as power filter capacitors, a USB connector, a reset button, an LED indicator, etc. Most of the available pins of the RP2040 chip are led out on both sides of the Pico development board, and four pins are used for internal functions, including driving the onboard LED, powering the development board, and selecting the BOOT mode.
The schematic diagram of the Raspberry Pi Pico is shown below, which consists of an external clock crystal oscillator circuit, a BOOT mode selection circuit, a power supply input circuit, a power supply voltage measurement circuit, an LED indicator driving circuit, a debugging interface circuit, a pin expansion circuit and a chip peripheral circuit, and these parts will be introduced one by one as follows.
Figure 1.4 Circuit Schematic of Raspberry Pi Pico Development Board
Simply put, the peripheral circuit of a Pico development board consists of the following parts:
Clock crystal oscillator circuit: A circuit composed of a 12MHz crystal oscillator (labeled X1 in the diagram) and small components such as capacitors. It acts as the "metronome" for the chip: all operations of the chip and its communication with peripheral devices require precise "time rhythm", and this circuit provides a stable beat signal of 12 million cycles per second to ensure the timing accuracy of the chip's operations — for example, the function of flashing an LED at a 1-millisecond interval entirely relies on this beat to calculate time.
BOOT Mode Selection Circuit: Essentially, it is a small circuit equipped with a BOOTSEL button, serving as the "boot mode toggle switch" for the chip, which has two modes during startup:
Normal Mode: Launch the saved program;
BOOT Mode: The firmware flashing state is the "program loading mode" of Pico: after connecting Pico to a computer while holding down the BOOTSEL button, Pico will switch to this state (without launching the old program), and at this point it will be recognized by the computer as a storage device. You only need to drag the written program (firmware) into it to install new functions for Pico.
Power Supply Input Circuit: This is the circuit in charge of power management (such as the power chip U2 in the diagram). We can connect it to a USB (5V) power source or a battery (2-5V); this circuit will stably convert the input voltage to the 3.3V required by the chips, filter out the clutter in the voltage, and prevent the chips from being damaged by fluctuating voltage.
Power Supply Voltage Measurement Circuit: A compact circuit designed to detect the power supply voltage. It acts as the "built-in voltmeter" of the board, capable of measuring the input power voltage in real time (for example, when powered by batteries, it lets you know if the batteries are running low), making it convenient for you to monitor the power status.
LED Indicator Driver Circuit: A small circuit for controlling the onboard LED. The chip can control the on/off state of this LED via the GPIO25 pin to indicate status (e. g., blinking when the program is running, steady-on when power is connected).
Debug Interface Circuit: This refers to the DEBUG header (3-pin header) shown in the diagram, which acts as the "fault diagnosis port" of the board. If your program gets corrupted or the board stops functioning, you can connect a debugging tool to this interface to check the internal operating status of the chip and pinpoint where the program has gone wrong.
Pin Extension Circuit: A circuit that converts chip pins into header pins (labeled CON_PICO_40W in the diagram). The pins on the RP2040 chip itself are extremely small and cannot accept wires directly; this circuit extends the chip pins into standard header pins, allowing you to directly connect DuPont wires to these pins to interface with external components such as sensors and motors.
Chip peripheral circuit: A circuit composed of small components such as filter capacitors and resistors around the chip. For example, filter capacitors can filter out clutter in the power supply to make the power supply for the chip more stable; resistors can protect pins from being burned out by excessive current, and prevent the chip from malfunctioning due to external interference or current fluctuations.
