We love using chips with 'native USB' peripherals - that's the magic silicon that lets a microcontroller act like an HID keyboard or mouse or disk drive or MIDI synth. It's a standard addition on SAMD21, RP2040, and even the latest ESP32-S2 and ESP32-S3 boards. But what about when you have a classic ATmega328 Uno? or an original ESP32 or ESP8266? Maybe even a single-board computer like a Raspberry Pi? We would say "sorry...that's not possible" UNTIL NOW! The CH9328 is a funky chip that is basically a programmed microcontroller that enumerates as an every-day HID keyboard and can convert ASCII or 8-byte raw reports, read over a standard serial port UART, into keypresses. So, you can emulate a keyboard even if your chip doesn't have native USB! You do need a hardware or software serial port: some way to generate 9600 baud 3V-logic signal that the CH9328 can read.