Audio ADC & DAC on Embedded Systems Development

ADC for Audio Capture

Mon, 01 Jan 0001 00:00:00 +0000

ADC for Audio Capture#

Most Cortex-M microcontrollers include a successive-approximation (SAR) ADC capable of sampling at rates well above audio requirements — a 12-bit ADC running at 1 MSPS is far faster than the 8–48 kHz needed for audio. The question is not whether the ADC is fast enough, but whether it is clean enough. Audio demands sustained, evenly spaced conversions with minimal noise over thousands of consecutive samples, while most MCU ADC specifications are optimized for single-shot or burst measurements of slowly changing signals. The gap between “ADC can sample at 48 kHz” and “ADC produces usable audio at 48 kHz” is measured in ENOB, noise floor, and clock jitter.

DAC Audio Output

Mon, 01 Jan 0001 00:00:00 +0000

DAC Audio Output#

An on-chip DAC converts digital audio samples back into an analog voltage waveform — the final step before an amplifier drives a speaker or headphone. Many Cortex-M MCUs include one or two 12-bit DAC channels (STM32F4, STM32H7, ESP32, RP2350), which can produce audio output without any external converter IC. The quality ceiling is set by the DAC resolution and output characteristics: a 12-bit DAC provides ~72 dB of theoretical dynamic range (10–11 ENOB in practice), sufficient for voice, notification sounds, and casual audio playback, but noticeably below CD quality for critical listening.

PWM Audio Output

Mon, 01 Jan 0001 00:00:00 +0000

PWM Audio Output#

Not every MCU has a DAC, but nearly every MCU has a PWM-capable timer. A PWM signal whose duty cycle is modulated by audio sample values, followed by a low-pass filter to remove the carrier frequency, produces an analog audio output. This technique is widely used on Cortex-M0 (no DAC), ATtiny/ATmega, RP2040 (which has PWM but no DAC), and other low-cost MCUs. The quality ceiling is lower than a dedicated DAC — limited by PWM resolution, carrier frequency harmonics, and reconstruction filter design — but for voice prompts, alarms, notification sounds, and simple music playback, PWM audio is a practical zero-cost solution.

External Audio ADCs & DACs

Mon, 01 Jan 0001 00:00:00 +0000

External Audio ADCs & DACs#

When on-chip conversion is not enough — the noise floor is too high, the resolution is too coarse, or the application demands audiophile-grade specifications — a dedicated external audio converter IC bridges the gap. These devices are purpose-built for audio: 24-bit sigma-delta converters with 100+ dB SNR, integrated anti-aliasing and reconstruction filters, ultra-low jitter clock circuitry, and precisely matched analog front-ends. The trade-off is additional board complexity (I2S bus, clock routing, power supply filtering) and cost ($1–10 per IC).