Below code i used in Arduino UNO worked flawlessly.
const int pwmPin = 9; // OC1A = Pin 9 on Arduino Uno
const float freqStart = 28000.0; // Hz
const float freqEnd = 24000.0; // Hz
const float freqStep = -10.0; // Hz
const float tonStart = 8.0; // μs
const float tonEnd = 21.0; // μs
const int delayMs = 5; // Delay per step
const int offDelayMs = 3000; // 5 sec OFF after sweep
void setup() {
 pinMode(pwmPin, OUTPUT);
 delay(2000);
 // Timer1: Phase Correct PWM, TOP = ICR1
 TCCR1A = _BV(COM1A1); // Non-inverting PWM on OC1A
 TCCR1B = _BV(WGM13) | _BV(CS10); // Mode 8: Phase-correct, no prescaler
 Serial.begin(115200);
}
void loop() {
 float freq = freqStart;
 float ton = tonStart;
 float freqRange = freqStart - freqEnd;
 float tonRange = tonEnd - tonStart;
 int steps = freqRange / -freqStep;
 for (int i = 0; i <= steps; i++) {
 freq = freqStart + i * freqStep;
 ton = tonStart + (tonRange * i / steps);
 float period_us = 1000000.0 / freq;
 uint16_t top = (16000000UL / (2 * freq)); // ICR1 value
 uint16_t duty = (ton / period_us) * top; // OCR1A value
 ICR1 = top;
 OCR1A = duty;
 Serial.print("Freq: ");
 Serial.print(freq, 1);
 Serial.print(" Hz | Ton: ");
 Serial.print(ton, 1);
 Serial.print(" us | TOP: ");
 Serial.print(top);
 Serial.print(" | OCR1A: ");
 Serial.println(duty);
 delay(delayMs);
 }
 // Turn off PWM
 OCR1A = 0;
 Serial.println("PWM OFF for 5 seconds");
 delay(offDelayMs);
}
Below code i used in ESP32-S3 but the wave is banging.
#include <Arduino.h>
#include <driver/rmt_tx.h>
#include <Ticker.h>
// --- Pin Setup ---
#define PWM_PIN 10 // Pick a reliable RMT-capable GPIO
// --- Sweep Parameters ---
const float freqStart = 28000.0;
const float freqEnd = 24000.0;
const float freqStep = -10.0;
const float tonStart = 8.0;
const float tonEnd = 21.0;
const int delayMs = 5;
const int offDelayMs = 5000;
rmt_channel_handle_t rmt_chan = nullptr;
rmt_encoder_handle_t rmt_encoder = nullptr;
void setupRMT(float freq, float ton_us) {
 if (rmt_chan) {
 rmt_disable(rmt_chan);
 rmt_del_channel(rmt_chan);
 rmt_chan = nullptr;
 }
 uint32_t period_us = 1000000.0 / freq;
 uint32_t toff_us = period_us - ton_us;
 rmt_tx_channel_config_t tx_config = {};
 tx_config.clk_src = RMT_CLK_SRC_DEFAULT;
 tx_config.gpio_num = (gpio_num_t)PWM_PIN;
 tx_config.mem_block_symbols = 64;
 tx_config.resolution_hz = 1000000; // 1 μs resolution
 tx_config.trans_queue_depth = 1;
 tx_config.flags.invert_out = false;
 tx_config.flags.with_dma = false;
 ESP_ERROR_CHECK(rmt_new_tx_channel(&tx_config, &rmt_chan));
 rmt_copy_encoder_config_t enc_config = {};
 ESP_ERROR_CHECK(rmt_new_copy_encoder(&enc_config, &rmt_encoder));
 ESP_ERROR_CHECK(rmt_enable(rmt_chan));
 rmt_symbol_word_t item;
 item.level0 = 1;
 item.duration0 = (uint16_t)ton_us;
 item.level1 = 0;
 item.duration1 = (uint16_t)toff_us;
 rmt_transmit_config_t config = {};
 config.loop_count = 1000;
 ESP_ERROR_CHECK(rmt_transmit(rmt_chan, rmt_encoder, &item, sizeof(item), &config));
}
void stopPWM() {
 if (rmt_chan) {
 rmt_disable(rmt_chan);
 gpio_reset_pin((gpio_num_t)PWM_PIN);
 gpio_set_direction((gpio_num_t)PWM_PIN, GPIO_MODE_OUTPUT);
 gpio_set_level((gpio_num_t)PWM_PIN, 0);
 rmt_del_channel(rmt_chan);
 rmt_chan = nullptr;
 }
}
void setup() {
 Serial.begin(115200);
 delay(2000);
 Serial.println("Starting PWM Sweep...");
}
void loop() {
 float freq = freqStart;
 float ton = tonStart;
 float freqRange = freqStart - freqEnd;
 float tonRange = tonEnd - tonStart;
 int steps = freqRange / -freqStep;
 for (int i = 0; i <= steps; i++) {
 freq = freqStart + i * freqStep;
 ton = tonStart + (tonRange * i / steps);
 setupRMT(freq, ton);
 float period_us = 1000000.0 / freq;
 Serial.printf("Freq: %.1f Hz | Ton: %.1f us | Period: %.1f us\n", freq, ton, period_us);
 delay(delayMs);
 }
 stopPWM();
 Serial.println("PWM OFF for 5 seconds");
 delay(offDelayMs);
}

No crash or backtrace. The issue is in waveform stability and timing.