If you’ve been following along with Curious Scientist’s blog series on the CH32V003F4P6 microcontroller, you’ll know things started simple: toggling GPIOs, chatting over USART, the usual MCU warm-up routine. But in the latest post, the author cranks things up a notch and introduces one of the most powerful—and arguably coolest—features of any microcontroller: timers and PWM.
PWM (Pulse-Width Modulation) might sound like a dry textbook term, but it’s basically the MCU equivalent of beating a drum at just the right rhythm and volume—fast enough to fool your ears, motors, or LEDs into thinking they’re hearing a smooth song. And on the CH32V003F4P6, that drum kit is the Advanced-Control Timer Module (ADTM), a 16-bit wizard that counts up, down, or both, while happily spitting out pulses, PWM signals, or even talking to encoders.
The blog walks through how this timer ties into the MCU’s 48 MHz clock (that’s a 20.83 ns heartbeat—yes, nanoseconds), and how registers like the Auto-Reload Register (ARR) and Capture-Compare Register (CCR) set the stage for PWM’s frequency and duty cycle. In practice? Want a 10 Hz PWM signal at 50% duty cycle? Just juggle the prescaler, ARR, and CCR until the math lands. Then configure your GPIO as a push-pull alternate function, and boom—you’ve got yourself a square wave that could dim an LED or make a servo twitch like it just drank too much coffee.
But before we get too cozy with the code, let’s zoom out. Because PWM didn’t just pop into existence with modern MCUs—it’s been on a bit of a journey.
A Short, Chaotic History of PWM
The idea of chopping something into pulses and calling it “control” is older than semiconductors themselves. Back in 1849, George Corliss patented his legendary steam engine design, which—believe it or not—used a PWM-ish trick to regulate valve timing. No microcontrollers, no silicon, just cast iron and industrial-era grit.
Fast-forward a century, and PWM found its way into telecommunications and space telemetry. NASA’s Explorer I in the 1950s was literally sending analog sensor data back to Earth by encoding it as variable pulse widths. Imagine your entire satellite health report being squeezed into something that looks like a jittery square wave.
By the 1960s and 70s, engineers realized PWM wasn’t just good for talking—it was fantastic for saving energy. Instead of wasting power with clunky rheostats, you could switch things on and off so quickly that motors and amplifiers thought they were getting a steady stream. Enter the era of switch-mode power supplies (SMPS). And the party really kicked off in 1976, when Silicon General released the SG1524—the first single-chip PWM controller. Suddenly, instead of wiring up half a lab bench to build a regulator, you could just drop in a neat little IC.
Of course, once engineers had their hands on this toy, things escalated quickly. By the 1980s, companies like Motorola and TI were cranking out PWM controllers (hello TL494), and Unitrode even introduced current-mode PWM, which not only responded faster but also added built-in current limiting. Translation: fewer blown transistors, more happy engineers.
Meanwhile, motor control folks weren’t about to miss out. Techniques like sine-triangle PWM popped up to make motors hum more smoothly. And in 1982, the brainy trio of Pfaff, Weschta, and Wick dropped Space Vector Modulation (SVM)—a PWM method so advanced it still sounds futuristic. Today, SVM is basically the secret sauce behind your quiet, efficient electric car motor.
By then, PWM had gone from “telemetry hack” to industrial rockstar. Variable-frequency drives (VFDs), pioneered in Finland during the 1960s, started running everything from metro trains to factory machines. And now? PWM is everywhere—your phone charger, your smart LED light, even the Class-D amplifier in your Bluetooth speaker blasting out that Friday night playlist.
