DD3 LoRa Bridge Raspi Debugger

Headless Raspberry Pi Zero W project:

• WiFi client or fallback AP (serial / serialserial)
• Web portal (http://192.168.4.1/ in AP mode)
• ESP32 USB serial bridge with live SSE stream and daily log files (/home/pi/xxx_YYYY-MM-DD_HH-MM-SS.log)
• Stable symlink to active log (/home/pi/xxx.log)
• RTC boot restore + NTP sync + RTC write-back
• Autostart via systemd

Current State

Current implementation status:

• Boot flow restores system time from RTC (hwclock -s) before starting logging.
• If WLAN + internet is unavailable, AP fallback starts on wlan0:
  • SSID: serial
  • Password: serialserial
  • AP IP: 192.168.4.1/24
  • DHCP range: 192.168.4.10 to 192.168.4.200
• Web portal is available on port 80:
  • / WiFi scan + connect UI
  • /serial live serial console (SSE via /events/serial)
• ESP32 serial bridge:
  • Auto-detects /dev/ttyUSB*, /dev/ttyACM*, /dev/serial/by-id/*
  • Reconnects automatically on unplug/replug
  • Daily log rollover at midnight with datetime filename
• Once internet is available, NTP sync runs and writes corrected time back to RTC (hwclock -w).

Runtime check commands:

systemctl status serial-bridge
journalctl -u serial-bridge -f
ip a show wlan0
ls -l /home/pi/xxx.log /home/pi/xxx_*.log
sudo hwclock -r

RTC GPIO Wiring (Raspberry Pi Zero W)

Use I2C1 pins on the 40-pin header:

RTC module pin	Raspberry Pi pin	BCM GPIO	Notes
VCC	Pin 1	3V3	Use 3.3V
GND	Pin 6	GND	Common ground
SDA	Pin 3	GPIO2 (SDA1)	I2C data
SCL	Pin 5	GPIO3 (SCL1)	I2C clock

Minimal pin marker (header top):

Pin 1 (3V3)   Pin 2 (5V)
Pin 3 (SDA1)  Pin 4 (5V)
Pin 5 (SCL1)  Pin 6 (GND)

Enable I2C + RTC overlay (example DS3231):

sudo raspi-config nonint do_i2c 0
echo 'dtoverlay=i2c-rtc,ds3231' | sudo tee -a /boot/firmware/config.txt
sudo reboot

Verify:

ls -l /dev/rtc0
sudo i2cdetect -y 1
sudo hwclock -r

Quick install (on Raspberry Pi)

chmod +x install.sh
sudo ./install.sh

Then reboot:

sudo reboot