python - ESP32-S2 XBee Communication Issue - Sending Data But Raspberry Pi Not Receiving - Stack Overflow

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I've set up a Zigbee IoT network using an ESP32-S2 Feather with BME280 as the sensor node and a Raspberry Pi with XBee 3 USB adapter as the coordinator. The ESP32 appears to be successfully sending data (according to serial monitor), but the Raspberry Pi isn't receiving anything.

Hardware Setup

Sensor Node: Adafruit ESP32-S2 Feather with built-in BME280 sensor XBee Module: Connected to ESP32-S2 via SoftwareSerial Coordinator: Raspberry Pi with Digi XBee 3 USB adapter

Connections

XBee Module        ESP32-S2 Feather
-----------        -----------------
DOUT (TX)    →     GPIO38 (RX)
DIN (RX)     →     GPIO39 (TX)
VCC (3.3V)   →     3.3V
GND          →     GND

XBee Configuration Both XBee modules are configured with:

API Mode: 1 Baud Rate: 9600 PAN ID: same for both USB in the pi and the xbee One is set as Coordinator (Pi), one as End Device (ESP32)

ESP32 Code

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>
#include <Adafruit_LC709203F.h>
#include <SoftwareSerial.h>

// LED for visual feedback
#define LED_PIN 13

// XBee communication pins
#define XBEE_RX 38
#define XBEE_TX 39

// Send interval (milliseconds)
#define SEND_INTERVAL 10000

// Create SoftwareSerial for XBee
SoftwareSerial xbeeSerial;

// Initialize sensors
Adafruit_BME280 bme;
Adafruit_LC709203F lc;

void setup() {
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, HIGH);
  
  Serial.begin(9600);
  delay(1000);
  
  // Initialize SoftwareSerial for XBee
  xbeeSerial.begin(9600, SWSERIAL_8N1, XBEE_RX, XBEE_TX, false);
  
  // Initialize BME280 sensor
  if (!bme.begin(0x77)) {
    Serial.println("BME280 sensor not found!");
    while(1) {
      digitalWrite(LED_PIN, HIGH);
      delay(100);
      digitalWrite(LED_PIN, LOW);
      delay(100);
    }
  }
  
  // Initialize battery monitor
  if (!lc.begin()) {
    Serial.println("Battery monitor not found!");
    while(1) {
      digitalWrite(LED_PIN, HIGH);
      delay(100);
      digitalWrite(LED_PIN, LOW);
      delay(100);
    }
  }
  
  digitalWrite(LED_PIN, LOW);
}

void loop() {
  // Read sensor data
  bme.takeForcedMeasurement();
  float temperature = bme.readTemperature();
  float humidity = bme.readHumidity();
  float pressure = bme.readPressure() / 100.0F;
  float batteryVolt = lc.cellVoltage();
  float batteryPct = lc.cellPercent();
  
  // Display data for debugging
  Serial.println("\nSensor readings:");
  Serial.print("Temperature: "); Serial.print(temperature); Serial.println(" °C");
  Serial.print("Humidity: "); Serial.print(humidity); Serial.println(" %");
  Serial.print("Pressure: "); Serial.print(pressure); Serial.println(" hPa");
  Serial.print("Battery: "); Serial.print(batteryVolt); Serial.print("V (");
  Serial.print(batteryPct); Serial.println("%)");
  
  // Send data via XBee
  digitalWrite(LED_PIN, HIGH);  // LED on during transmission
  
  // Format data as string
  char dataString[100];
  sprintf(dataString, "T:%.2f,H:%.2f,P:%.2f,V:%.2f,B:%.2f", 
          temperature, humidity, pressure, batteryVolt, batteryPct);
  
  // Send string data
  xbeeSerial.println(dataString);
  xbeeSerial.flush();
  
  digitalWrite(LED_PIN, LOW);
  Serial.println("Data sent!");
  
  delay(SEND_INTERVAL);
}

Raspberry Pi Code

#!/usr/bin/env python3
"""
Simple XBee Serial Receiver for Raspberry Pi
Receives formatted string data from ESP32 sensor
"""

import serial
import time
import csv
import os
from datetime import datetime

# Configuration
PORT = "/dev/ttyUSB1"  # Change if needed
BAUD_RATE = 9600
DATA_FILE = "sensor_data.csv"

def timestamp():
    """Get current timestamp as string"""
    return datetime.now().strftime("%Y-%m-%d %H:%M:%S")

def find_usb_port():
    """Find available USB port"""
    import glob
    ports = glob.glob("/dev/ttyUSB*") + glob.glob("/dev/ttyACM*")
    if ports:
        return ports[0]
    return None

def save_data(data_dict):
    """Save data to CSV file"""
    file_exists = os.path.isfile(DATA_FILE)
    
    with open(DATA_FILE, 'a', newline='') as csvfile:
        fieldnames = ['timestamp', 'temperature', 'humidity', 
                     'pressure', 'battery_voltage', 'battery_percent']
        writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
        
        if not file_exists:
            writer.writeheader()
        
        writer.writerow(data_dict)

def parse_data(data_string):
    """Parse data string in format T:23.45,H:45.67,P:1013.25,V:3.82,B:94.50"""
    data_dict = {'timestamp': timestamp()}
    
    try:
        # Split parts by comma
        parts = data_string.strip().split(',')
        
        # Process each part
        for part in parts:
            key, value = part.split(':')
            if key == 'T':
                data_dict['temperature'] = float(value)
            elif key == 'H':
                data_dict['humidity'] = float(value)
            elif key == 'P':
                data_dict['pressure'] = float(value)
            elif key == 'V':
                data_dict['battery_voltage'] = float(value)
            elif key == 'B':
                data_dict['battery_percent'] = float(value)
        
        return data_dict
    except Exception as e:
        print(f"Error parsing data: {e}")
        print(f"Raw data: {data_string}")
        return None

def main():
    """Main function"""
    print(f"[{timestamp()}] Starting Simple XBee Receiver")
    
    # Find USB port if needed
    global PORT
    if not os.path.exists(PORT):
        PORT = find_usb_port()
        if not PORT:
            print("No USB device found!")
            return
    
    print(f"[{timestamp()}] Opening serial port {PORT}")
    
    try:
        # Open serial port
        ser = serial.Serial(PORT, BAUD_RATE, timeout=1)
        print(f"[{timestamp()}] Serial port opened successfully")
        print(f"[{timestamp()}] Waiting for data...")
        
        # Main loop
        buffer = ""
        while True:
            # Read data if available
            if ser.in_waiting > 0:
                char = ser.read(1).decode('utf-8', errors='ignore')
                
                # Add character to buffer
                buffer += char
                
                # Process complete line
                if char == '\n':
                    print(f"[{timestamp()}] Received: {buffer.strip()}")
                    
                    # Parse and save data
                    data = parse_data(buffer)
                    if data:
                        print(f"[{timestamp()}] Temperature: {data['temperature']}°C")
                        print(f"[{timestamp()}] Humidity: {data['humidity']}%")
                        print(f"[{timestamp()}] Pressure: {data['pressure']} hPa")
                        print(f"[{timestamp()}] Battery: {data['battery_voltage']}V ({data['battery_percent']}%)")
                        
                        # Save to CSV
                        save_data(data)
                        print(f"[{timestamp()}] Data saved to {DATA_FILE}")
                    
                    # Reset buffer
                    buffer = ""
            
            # Short delay
            time.sleep(0.01)
            
    except KeyboardInterrupt:
        print(f"[{timestamp()}] Program stopped by user")
    except Exception as e:
        print(f"[{timestamp()}] Error: {e}")
    finally:
        # Close serial port if open
        if 'ser' in locals() and ser.is_open:
            ser.close()
            print(f"[{timestamp()}] Serial port closed")

if __name__ == "__main__":
    main()

What I've Observed

The ESP32 serial monitor confirms it's reading the sensor data and sending it The LED on the ESP32 blinks as expected during transmission The Raspberry Pi script is running and correctly using the USB port Nothing appears in the Raspberry Pi's receiver logs

What I've Tried

Verified XBee configurations in XCTU Confirmed the baud rates match (9600) Ensured API mode is enabled on both XBees Verified the correct pin connections (RX=GPIO38, TX=GPIO39) Tested the ESP32's ability to read sensor data (working correctly) Placed devices close to each other (~3 feet apart)

Question

How do we solve this issue and make sure that the esp32s2 is sending the data to the pi through the xbee module placed on a hat and connecting wirely to the esp32s2?

Any insights would be greatly appreciated, especially from those with experience using XBee modules with ESP32-S2 boards!

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