SWYoon Labs

Series navigation: Episode 1: The Roadmap · Episode 7: Reading Arduino Pin-Current Specifications · Episode 9 The problem: The LCD backlight turns on, but the screen remains white. The goal: Separate display power from successful SPI communication and initialization. The result: A checklist for SCK, MOSI, MISO, CS, D/C, RESET, voltage, clock mode, and command order. AI-generated illustration of a low-voltage SPI debugging setup. Verify wiring against the exact display-controller data sheet. The backlight was on, so I assumed the LCD was working I connected a color display. It lit immediately, but the entire panel stayed white. The result is misleading. The backlight is often a separate load. It can receive power while the display controller is unpowered, held in reset, never selected, wired incorrectly, or receiving the wrong initialization. A white screen does not mean “SPI is almost working.” It only proves that light passes through the panel. What each wire does...

Series navigation: Episode 1: The Roadmap · Episode 7: Reading Arduino Pin-Current Specifications · Episode 8 The problem: A terminal shows random symbols even though both devices say “UART.” The goal: Understand what must match electrically and logically before bytes become readable text. The result: A debugging order for TX/RX, ground, voltage, baud rate, frame format, buffering, and signal capture. AI-generated illustration of a low-voltage UART bench. It is not a measurement record or exact wiring guide. The terminal opened, but the text looked broken UART is often the first communication interface I use on a board. It prints boot messages, accepts commands, connects two controllers, or talks to a GPS, modem, Bluetooth module, serial display, or USB-to-serial adapter. Then the terminal shows this: text ��H�l� The program may be sending Hello , but UART does not transmit software strings. It places timed voltage levels on a wire. The receiver must agree about vo...

Series navigation: Episode 1: The Roadmap · Episode 2: Digital Multimeter and LED Circuit · Episode 3: Voltage Divider Under Load · Episode 4: What an Oscilloscope Shows · Episode 5: How Arduino Reads Sensor Voltage · Episode 6: Why Arduino Cannot Drive a Motor Directly · Episode 7 The surprising part: The ATmega328P data sheet contains a 40 mA-per-pin number, but designing an Arduino output to operate at 40 mA is the wrong conclusion. What you will learn: How to tell a damage boundary from a usable operating specification and turn one design question into a short path through a long data sheet. What you will be able to do: Identify the exact device and package, read conditions and footnotes, and record a defensible design decision instead of copying the first number you find. AI-generated illustration of a data-sheet-reading workflow. The tables are visual placeholders, not copied specifications; use the manufacturer's current document for design values. Reader...

Series navigation: Episode 1: The Roadmap · Episode 2: Digital Multimeter and LED Circuit · Episode 3: Voltage Divider Under Load · Episode 4: What an Oscilloscope Shows · Episode 5: How Arduino Reads Sensor Voltage · Episode 6 What you will learn: Why a GPIO pin can send a command but should not supply a motor's power. What problem it solves: A motor may fail to start, reset the board, overheat an output pin, or damage the controller when connected directly. What you will be able to do: Explain a low-side N-channel MOSFET circuit, choose parts from their important ratings, and identify where motor current flows when switching on and off. AI-generated instructional image of a typical low-voltage workbench. It is not a wiring reference or a photograph of a circuit tested for this article; use the schematic below for connections. Reader guide Indicator Details Article type Power-interface concept and design checklist Reading time About 12 minutes ...

Series navigation: Episode 1: The Roadmap · Episode 2: Digital Multimeter and LED Circuit · Episode 3: Voltage Divider Under Load · Episode 4: What an Oscilloscope Shows · Episode 5 What you will learn: How a changing voltage becomes an integer inside an Arduino sketch. What problem it solves: Sensor readings often move even when the physical world appears still. What you will be able to do: Wire a potentiometer to A0, interpret a raw ADC code, estimate its input voltage, and decide whether smoothing is appropriate. AI-generated instructional image of a typical low-voltage setup. It is not a photograph of measurements performed for this article. Reader guide Indicator Details Article type Concept guide with an optional low-voltage exercise Reading time About 10 minutes Difficulty 2/5 — Beginner Hands-on time Optional; about 15 minutes Parts Arduino Uno R3 example, 10 kΩ potentiometer, breadboard, jumper wires Prerequisite Basic voltage a...