This project delivers a network monitoring appliance that passively observes and visualizes Wi-Fi traffic in real time. By combining a Raspberry Pi configured as both a hotspot and uplink bridge to the LAN's router, with an ESP32-driven TFT display, the system can:

• Serve as a portable Wi-Fi AP for client devices
• Forward upstream traffic through an external USB Wi-Fi adapter to the main router
• Gather uplink metrics (throughput, client list, CPU temperature, signal quality, memory) on the Pi
• Stream these statistics over UDP to the ESP32
• Render intuitive graphs and status screens on a 1.44″ ST7735S LCD

This standalone solution is ideal for home network troubleshooting.

The overall architecture comprises two collaborating units:

* Raspberry Pi Zero 2 W

• Built-in Wi-Fi in AP mode (SSID “PiAP”) for local devices
• USB Wi-Fi adapter in station mode to uplink traffic to the main router
• Passive capture of 802.11 frames and system telemetry
• Computes per-second uplink throughput, active client list (IP+MAC), CPU temperature, signal strength, free memory
• Sends a compact JSON payload via UDP to the ESP32 every second

* ESP32 + TFT LCD

• Joins the Pi’s hotspot as a station client
• Listens on UDP port 4000 for incoming JSON metrics
• Maintains a 128-sample circular buffer for RX/TX history
• Dynamically autoscale graphs to current network load
• Offers three UI modes toggled by a push-button:

• Real-time throughput graph
• Connected clients list
• System info dashboard

https://github.com/robert-ercean/Network_Monitor

• ESP32 Firmware: PlatformIO (VS Code) with Arduino-ESP32 core
• Pi Scripts: Python and Bash scripts edited via Nano on Raspbian GNU/Linux

* ESP32 Side

• Core networking: `WiFi.h`, `WiFiUdp.h`
• JSON handling: ArduinoJson v6
• Display driver: TFT_eSPI (ST7735S)
• ESP IDF SOC register macros: `soc/gpio_reg.h`, `soc/ledc_struct.h`, etc.

* Raspberry Pi Side

• Python stdlib: `socket`, `time`, `pathlib`, `signal`, `sys`, `subprocess`
• System tools:
  • `iw dev <iface> station dump` → associated MAC addresses
  • `/proc/net/arp` → ARP cache for MAC→IP
  • Sysfs: network stats & temperature

* Circular buffer (size 128 i.e. max width of the LCD)

• Stores the latest second-by-second RX/TX values
• Overwrites oldest sample when full, mapping one pixel per sample

* Graph autoscaling

• Exponential smoothing adapts the Y-axis scale to recent peaks
• Keeps the plotted curves filling the display area

* Bare-metal PWM feedback

• 5 kHz, 8-bit resolution via LEDC timer0/channel0
• Red LED brightness proportional to (RX+TX) load

* Debounced button input

• Debounce interval 250 ms in interrupt routine
• Cycles UI mode on each valid press

1. Boot & Initialization

• Configure serial debug UART
• Initialize GPIO pins and PWM registers directly
• Setup TFT display and show splash screen
• Connect as Wi-Fi station to Pi’s AP (SSID=“PiAP”)
• Open UDP listener on port 4000

2. Data Acquisition (Pi Script)

• Each second:
  • Read `/sys/class/net/<uplink>/statistics/{rx,tx}_bytes` → compute bits/sec
  • List associated stations via `iw station dump`
  • Lookup each MAC in `/proc/net/arp` for its IP
  • Read CPU temp and free memory from sysfs
  • Query link RSSI via `iw dev <uplink> link`
  • Send JSON packet to ESP32

3. ESP32 Main Loop

• Wait for UDP packet → parse JSON
• Push new RX/TX into circular buffer
• Update LED PWM based on current throughput

• Renders selected view:
  • Graph: dynamic RX/TX curves + scale/peak labels
  • Clients: IP & MAC of each connected device
  • Info: CPU temperature, RSSI, available RAM

4. Mode Switching

• Push-button interrupt toggles the display mode
• Debounce logic ensures clean transitions