Hardware Integration Skill

Hardware Integration Skill

Complete reference for camera, GPIO, USB, and hardware integration on Raspberry Pi 5 for the PhotoBooth application.

Quick Reference

• Camera: iPad via getUserMedia (browser-based capture)
• Printer: Canon Selphy CP1500 via USB/​CUPS
• Network: Wi-Fi AP mode (hostapd)
• Storage: 256GB microSD

Raspberry Pi 5 Specifications

Camera Integration

The PhotoBooth uses iPad Air as the camera device via browser's getUserMedia API.

Camera Constraints (Frontend)

const constraints: MediaStreamConstraints = {
  video: {
    facingMode: 'user',           // Front camera for selfies
    width: { ideal: 1920 },       // Full HD
    height: { ideal: 1080 },
    frameRate: { ideal: 30 }
  },
  audio: false
};

Camera Testing

# On iPad (Safari DevTools):
# Check getUserMedia support
navigator.mediaDevices.getUserMedia({ video: true })
  .then(stream => console.log('Camera OK'))
  .catch(err => console.error('Camera Error:', err));

USB Device Management

List USB Devices

# List all USB devices
lsusb

# Detailed info
lsusb -v | grep -A 10 "Canon"

# Check USB device tree
lsusb -t

USB Troubleshooting

# Check kernel messages for USB
dmesg | grep -i usb | tail -20

# Reset USB bus (if device not responding)
sudo usbreset /​dev/​bus/​usb/​001/​002  # Replace with actual device

Network (Wi-Fi AP Mode)

Configuration Files

• /​etc/​hostapd/​hostapd.conf - AP configuration
• /​etc/​dnsmasq.conf - DHCP configuration
• /​etc/​dhcpcd.conf - Static IP for wlan0

hostapd Configuration

interface=wlan0
driver=nl80211
ssid=photobooth
hw_mode=g
channel=7
wmm_enabled=0
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=photobooth-1998
wpa_key_mgmt=WPA-PSK
rsn_pairwise=CCMP

Network Testing

# Check Wi-Fi AP status
sudo systemctl status hostapd

# List connected clients
iw dev wlan0 station dump

# Check IP assignments
cat /​var/​lib/​misc/​dnsmasq.leases

System Diagnostics

Temperature Monitoring

# CPU temperature
vcgencmd measure_temp

# Continuous monitoring
watch -n 1 vcgencmd measure_temp

Memory and CPU

# Memory usage
free -h

# CPU usage
top -bn1 | head -20

# Disk usage
df -h

Service Status

# Check all PhotoBooth services
sudo systemctl status hostapd
sudo systemctl status dnsmasq
sudo systemctl status cups
sudo systemctl status photobooth-backend
sudo systemctl status photobooth-frontend

Common Issues & Solutions

Issue: Camera not accessible from browser

Cause: HTTPS required for getUserMedia on non-localhost Solution:

1. Use self-signed certificate for HTTPS
2. Or add exception in Safari settings
3. Or use localhost with port forwarding

Issue: USB device not detected

Cause: Power issues or driver problems Solution:

# Check USB power
vcgencmd get_throttled

# Reload USB driver
sudo modprobe -r usb_storage && sudo modprobe usb_storage

# Check dmesg for errors
dmesg | tail -50

Issue: Wi-Fi AP not starting

Cause: Interface conflict or config error Solution:

# Check for conflicts
sudo rfkill list

# Unblock if blocked
sudo rfkill unblock wifi

# Restart hostapd
sudo systemctl restart hostapd

Issue: High CPU temperature

Cause: Inadequate cooling or high load Solution:

# Check temperature
vcgencmd measure_temp

# If > 80°C, reduce CPU frequency temporarily
echo 1500000 | sudo tee /​sys/​devices/​system/​cpu/​cpu0/​cpufreq/​scaling_max_freq

Hardware Test Script

Create /​home/​pi/​scripts/​test-hardware.sh:

#!/​bin/​bash
echo "=== PhotoBooth Hardware Diagnostics ==="
echo ""
echo "CPU Temperature: $(vcgencmd measure_temp)"
echo "Memory: $(free -h | grep Mem | awk '{print $3"/"$2}')"
echo "Disk: $(df -h / | tail -1 | awk '{print $3"/"$2" ("$5" used)"}')"
echo ""
echo "=== USB Devices ==="
lsusb | grep -v "hub" || echo "No non-hub USB devices"
echo ""
echo "=== Network ==="
echo "Wi-Fi AP: $(systemctl is-active hostapd)"
echo "DHCP: $(systemctl is-active dnsmasq)"
echo "Connected clients: $(iw dev wlan0 station dump 2>/​dev/​null | grep Station | wc -l)"
echo ""
echo "=== Services ==="
echo "CUPS: $(systemctl is-active cups)"
echo "Backend: $(systemctl is-active photobooth-backend 2>/​dev/​null || echo 'not configured')"
echo ""
echo "=== Diagnostics Complete ==="

Related Documentation

• docs/​DEPLOYMENT.md - Full deployment guide
• docs/​ERROR_CODES.md - Hardware error codes (PRINTER_, STORAGE_)
• docs/​use-cases/​UC-205-health-check.md - Health monitoring