Recording data from two adxl345 sensors

Any recommendation regarding the visualisation of the data?

another question - Is there a way to "translate" this ADXL345 data of x y z into frequency?

ESP32S3 code:

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>
#include <WiFi.h>
#include <esp_now.h>

Adafruit_ADXL345_Unified accel1 = Adafruit_ADXL345_Unified(1);

const float THRESHOLD           = 0.01;
const float RANGE               = 2.0;
const float ALPHA               = 0.2;
const int   CALIBRATION_SAMPLES = 100;

uint8_t receiverMAC[] = {0x68, 0xEE, 0x8F, 0x46, 0x4E, 0x34};

typedef struct {
  float x;
  float y;
  float z;
} SensorData;

SensorData dataToSend;
bool sensor1ok = false;

struct SensorState {
  float centerX = 0, centerY = 0, centerZ = 9.8;
  float prevX   = 0.5, prevY = 0.5, prevZ = 0.5;
  float filtX   = 0.5, filtY = 0.5, filtZ = 0.5;
};

SensorState s1;

void onSent(const wifi_tx_info_t *info, esp_now_send_status_t status) {}

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  delay(1000);

  // Init ESP-NOW
  WiFi.mode(WIFI_STA);
  if (esp_now_init() != ESP_OK) { Serial.println("ESP-NOW init failed"); while(1); }
  esp_now_register_send_cb(onSent);

  // Add receiver peer
  esp_now_peer_info_t peerInfo = {};
  memcpy(peerInfo.peer_addr, receiverMAC, 6);
  peerInfo.channel = 0;
  peerInfo.encrypt = false;
  if (esp_now_add_peer(&peerInfo) != ESP_OK) { Serial.println("Failed to add peer"); while(1); }

  Wire.begin();
  scanI2C();
  initSensors();
  calibrate();
  blinkLED(3, 200);
  Serial.end();
}

void loop() {
  heartbeat();
  if (sensor1ok) readAndSend(accel1, s1);
  delay(20);
}

float normalize(float value, float center) {
  float n = 0.5 + (value - center) / (2.0 * RANGE);
  if (n < 0.0) n = 0.0;
  if (n > 1.0) n = 1.0;
  return n;
}

void readAndSend(Adafruit_ADXL345_Unified &accel, SensorState &s) {
  sensors_event_t event;
  accel.getEvent(&event);

  float nx = normalize(event.acceleration.x, s.centerX);
  float ny = normalize(event.acceleration.y, s.centerY);
  float nz = normalize(event.acceleration.z, s.centerZ);

  // Low pass filter
  s.filtX = ALPHA * nx + (1 - ALPHA) * s.filtX;
  s.filtY = ALPHA * ny + (1 - ALPHA) * s.filtY;
  s.filtZ = ALPHA * nz + (1 - ALPHA) * s.filtZ;

  bool changed = false;
  if (abs(s.filtX - s.prevX) > THRESHOLD) { s.prevX = s.filtX; changed = true; }
  if (abs(s.filtY - s.prevY) > THRESHOLD) { s.prevY = s.filtY; changed = true; }
  if (abs(s.filtZ - s.prevZ) > THRESHOLD) { s.prevZ = s.filtZ; changed = true; }

  if (changed) {
    // Send via ESP-NOW
    dataToSend.x = s.filtX;
    dataToSend.y = s.filtY;
    dataToSend.z = s.filtZ;
    esp_now_send(receiverMAC, (uint8_t *)&dataToSend, sizeof(dataToSend));

    // Debug print
    Serial.print("X1 "); Serial.print(s.filtX, 3);
    Serial.print(",Y1 "); Serial.print(s.filtY, 3);
    Serial.print(",Z1 "); Serial.println(s.filtZ, 3);
  }
}

void calibrate() {
  Serial.println(F("Calibrating..."));
  float sx = 0, sy = 0, sz = 0;

  for (int i = 0; i < CALIBRATION_SAMPLES; i++) {
    sensors_event_t event;
    if (sensor1ok) {
      accel1.getEvent(&event);
      sx += event.acceleration.x;
      sy += event.acceleration.y;
      sz += event.acceleration.z;
    }
    delay(20);
  }

  if (sensor1ok) {
    s1.centerX = sx / CALIBRATION_SAMPLES;
    s1.centerY = sy / CALIBRATION_SAMPLES;
    s1.centerZ = sz / CALIBRATION_SAMPLES;
    Serial.print(F("Center X:")); Serial.print(s1.centerX, 2);
    Serial.print(F(" Y:")); Serial.print(s1.centerY, 2);
    Serial.print(F(" Z:")); Serial.println(s1.centerZ, 2);
  }

  Serial.println(F("Ready."));
}

void blinkLED(int times, int ms) {
  for (int i = 0; i < times; i++) {
    digitalWrite(LED_BUILTIN, HIGH); delay(ms);
    digitalWrite(LED_BUILTIN, LOW);  delay(ms);
  }
}

void heartbeat() {
  static unsigned long last = 0;
  unsigned long now = millis();
  if (now - last >= 500) {
    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
    last = now;
  }
}

void scanI2C() {
  Serial.println(F("Scanning I2C..."));
  int found = 0;
  for (byte addr = 1; addr < 127; addr++) {
    Wire.beginTransmission(addr);
    if (Wire.endTransmission() == 0) {
      Serial.print(F("  Found: 0x"));
      Serial.println(addr, HEX);
      found++;
    }
  }
  if (found == 0) Serial.println(F("  No I2C devices found"));
  Serial.println(F("---"));
}

void initSensors() {
  sensor1ok = accel1.begin(0x53);
  if (sensor1ok) {
    accel1.setRange(ADXL345_RANGE_2_G);
    Serial.println(F("Sensor 1 OK"));
  } else {
    Serial.println(F("WARNING: Sensor 1 not found"));
  }
}