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Oscilloscope vs Logic Analyzer — this is a common dilemma faced by every embedded developer or electronics enthusiast when debugging signals. Although both tools allow you to “view signals,” their purposes are fundamentally different: one focuses on visualizing analog waveforms, while the other specializes in digital logic signal edge detection and timing decoding. Especially when developing with microcontrollers like the ESP32, the differences in application scenarios, sampling methods, and analysis capabilities become very clear.

This article will guide you through a detailed comparison of these two tools’ principles and use cases. It will also explore how to build low-cost oscilloscopes or logic analyzers on the ESP32 platform, including recommended open-source projects, sampling limitations, and selection advice. Whether you are a maker, engineer, or simply an electronics hobbyist interested in signal observation, you will find practical references here.

What is an Oscilloscope? What is a Logic Analyzer?

An Oscilloscope is an instrument used to observe analog signal changes, displaying voltage waveforms over time in real time. It is suitable for viewing continuously varying signals such as sensor outputs, PWM signals, and power supply voltage fluctuations. You can clearly see waveform shapes, amplitudes, frequencies, and even noise or glitches, which are critical for debugging analog circuits.

In contrast, a Logic Analyzer is designed specifically to capture and analyze digital signals. It can simultaneously monitor multiple digital pins’ state changes and decode communication protocols like I²C, SPI, and UART, helping you understand communication content and timing accuracy. Unlike oscilloscopes that show continuous voltage changes, logic analyzers record whether a signal is 0 or 1 and the timing of transitions.

Simply put:

• Oscilloscopes excel at viewing waveforms and analyzing voltage changes.
• Logic analyzers excel at viewing data, tracking communication protocols and digital logic.

Differences Between Oscilloscope and Logic Analyzer

Although the ESP32-S3 is not a professional oscilloscope or logic analyzer, its powerful processing capabilities and rich hardware resources allow it to implement some features of both tools. Below is a comparison of their functions based on hardware performance and practical use cases:

Oscilloscope Functions (using ADC):

• Maximum sampling rate: about 500 kSPS to 1 MSPS (single channel with I2S + DMA)
• Frequency resolution: below ~100 kHz (Nyquist theory requires sampling rate to be at least twice the signal frequency)
• ADC resolution: 12 bits (effective number of bits ~9–10 bits)
• Input voltage range: 0–3.3 V (requires voltage divider if exceeded)
• Multi-channel support: limited, simultaneous sampling reduces speed and stability
• Stability: Sampling is susceptible to interference from Wi-Fi, USB, and system interrupts, affecting data continuity and accuracy
• Suitable scenarios: low-frequency analog signal monitoring, e.g., sensor outputs, slowly changing PWM waveforms, and voltage trend monitoring

Logic Analyzer Functions (using GPIO, RMT, I2S):

• Sampling rate: can reach several MHz, depending on technical implementation and software optimization
• Multi-channel support: supports simultaneous sampling on multiple channels, highly flexible
• Digital signal decoding: can use open-source tools (such as PulseView and sigrok) for decoding I²C, SPI, UART, and timing analysis
• Advantages: excels in digital logic signal capture and debugging, greatly aiding development workflows
• Suitable scenarios: debugging digital communication protocols, analyzing PWM output, infrared decoding, and other digital signal monitoring

ESP32 Oscilloscope

For the ESP32-S3, the built-in 12-bit ADC is the core of the oscilloscope function:

• ADC: up to about 1 MSPS (single channel, combined with I2S + DMA)
• I2S: used to read data stably and quickly from ADC, improving sampling continuity
• Voltage range: 0–3.3 V, voltage divider needed if exceeded
• Limitations: simultaneous multi-channel sampling reduces speed; sampling easily affected by Wi-Fi and system interruptions
• Suitable for low-frequency analog waveform monitoring, such as sensor signals or PWM outputs

ESP32 Logic Analyzer

For digital signal analysis, the ESP32-S3 offers more hardware support:

• GPIO: multiple channels can capture digital signals
• RMT module: hardware timer captures PWM, infrared pulses, providing precise timestamps
• I2S: high-speed parallel data capture enabling synchronized multi-channel logic sampling
• Interrupt system: quickly detects digital signal state changes, improving capture efficiency
• Rich hardware resources make it suitable for digital protocol decoding, PWM analysis, and logic signal monitoring

What is the RMT Module?

The RMT (Remote Control Peripheral) module is a hardware peripheral built into the ESP32 chip, designed to precisely generate and receive pulse signals. It operates independently from the CPU, using hardware timers to control the high and low signal durations, enabling high-resolution pulse width measurement and generation.

Main features of the RMT module:

• Accurate pulse signal capture: measures high and low durations, suitable for infrared remote controls, PWM pulse analysis, etc.
• Efficient waveform output: generates pulses with specific frequency and width, used in IR transmission or other remote control applications
• CPU resource saving: hardware operates independently without continuous CPU monitoring, reducing processing load
• Multi-channel support: simultaneously manages multiple input and output signals

Why is RMT suitable for logic analyzers?

Because it can precisely record the duration of high and low digital signal levels, capturing fast and subtle logic changes. This makes it ideal for decoding digital communication protocols (such as I2C, SPI, PWM), improving signal capture accuracy and efficiency.

ESP32-S3 RMT Module Simple Example

Initialize RMT Receiver

#define RMT_RX_CHANNEL    RMT_CHANNEL_0
#define RMT_RX_GPIO_NUM   18  // Adjust to your actual hardware GPIO pin
#define RMT_CLK_DIV       80  // Clock divider (80 division = 1us timing resolution)

void rmt_rx_init() {
    rmt_config_t rmt_rx;
    rmt_rx.channel = RMT_RX_CHANNEL;     // Select RMT channel for receiving
    rmt_rx.gpio_num = RMT_RX_GPIO_NUM;   // Assign GPIO number for RMT input
    rmt_rx.clk_div = RMT_CLK_DIV;         // Set clock divider for timing resolution
    rmt_rx.mem_block_num = 1;             // Use one memory block for RMT
    rmt_rx.rmt_mode = RMT_MODE_RX;        // Configure RMT as receiver mode
    rmt_rx.rx_config.filter_en = true;    // Enable filter to ignore short pulses
    rmt_rx.rx_config.filter_ticks_thresh = 100;  // Filter pulses shorter than this threshold (in ticks)
    rmt_rx.rx_config.idle_threshold = 10000;      // Idle threshold for end of signal detection (in ticks)
    rmt_config(&rmt_rx);                   // Apply RMT configuration
    rmt_driver_install(rmt_rx.channel, 1000, 0);  // Install RMT driver with 1KB buffer, no ISR
}

Receive and Parse Pulses

#include "esp_log.h"
static const char *TAG = "RMT_RECEIVE";

void rmt_receive_pulse() {
    rmt_item32_t items[64];
    size_t rx_size = 0;
    
    // Wait to receive data with a 100ms timeout
    esp_err_t ret = rmt_read_items(RMT_RX_CHANNEL, items, 64, 100 / portTICK_PERIOD_MS);
    if (ret == ESP_OK) {
        for (int i = 0; i < 64; i++) {
            // items[i].duration0 and items[i].duration1 represent the duration of high and low levels respectively (in units defined by clk_div)
            ESP_LOGI(TAG, "Pulse %d: high %d us, low %d us", i, items[i].duration0, items[i].duration1);
        }
    }
}

Main Program Example

void app_main() {
    rmt_rx_init();
    while (1) {
        rmt_receive_pulse();
        vTaskDelay(pdMS_TO_TICKS(500));
    }
}

Conclusion

While the ESP32-S3 is not a professional-grade oscilloscope or logic analyzer, its built-in hardware modules such as ADC and RMT allow it to perform well in low-frequency waveform monitoring and digital signal analysis.

If your main focus is on analog waveform observation, the ESP32-S3’s ADC combined with I2S DMA is a solid choice. For digital signal capture and protocol decoding, the RMT module along with multi-channel GPIO input is more suitable.

By selecting the right solution based on your application needs, you can accomplish versatile signal analysis tasks with a low-cost development board — making it ideal for DIY projects, learning, and entry-level development.

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