majiayu000 Dual-Controller Synchronization Guide
When to Use This Skill
Apply this skill when the user:
- Has issues with I2C communication between main and camera controllers
- Needs to debug the dual-ESP32 robocar architecture
- Wants to monitor both controllers simultaneously
- Experiences timing or synchronization issues
Architecture Overview
┌─────────────────────┐ I2C ┌─────────────────────┐
│ Main Controller │◄────────────►│ Camera Module │
│ Heltec WiFi LoRa │ │ ESP32-CAM │
│ │ │ │
│ - AI decisions │ │ - Image capture │
│ - Motor control │ │ - Vision analysis │
│ - LoRa comms │ │ - I2C slave │
└─────────────────────┘ └─────────────────────┘
Build Both Controllers
# Build main controller
make robocar-build-main
# Build camera module
make robocar-build-cam
# Or build both
make robocar-build-all
Monitor Both Controllers
Two Terminal Setup
Open two terminals and monitor both:
Terminal 1 - Main Controller:
make robocar-monitor-main PORT=/dev/cu.usbserial-0001
Terminal 2 - Camera Module:
make robocar-monitor-cam PORT=/dev/cu.usbserial-0002
Identifying Ports
If unsure which device is which:
ls -la /dev/cu.usbserial-* /dev/ttyUSB*
Look for:
- Device that appears first after connecting main controller
- Device that appears after connecting camera module
I2C Communication Debugging
Common I2C Issues
| Symptom | Possible Cause | Solution |
|---|---|---|
| No response | Wrong address | Verify 7-bit address format |
| Timeout | Missing pull-ups | Add 4.7K resistors on SDA/SCL |
| Corrupted data | Speed too fast | Reduce I2C clock frequency |
| Intermittent | Loose connection | Check wiring |
I2C Address Configuration
Ensure both controllers use the same address:
Main controller (master):
#define CAMERA_I2C_ADDR 0x55 // 7-bit address
Camera module (slave):
#define I2C_SLAVE_ADDR 0x55 // Must match master
Verify I2C Wiring
Main Controller Camera Module
SDA (21) ◄──────────► SDA (GPIO)
SCL (22) ◄──────────► SCL (GPIO)
GND ◄──────────► GND
Pull-up resistors (4.7K) on SDA and SCL to 3.3V.
Protocol Debugging
Expected Communication Pattern
- Main sends command byte
- Camera processes command
- Camera sends response
- Main reads response
Debug Logging
Enable verbose I2C logging in both projects:
esp_log_level_set("i2c", ESP_LOG_DEBUG);
Look for matching transactions:
- Main: "Sent command 0x01 to 0x55"
- Camera: "Received command 0x01"
Timing Issues
If commands arrive too fast:
Add delay between commands:
i2c_master_cmd_begin(I2C_NUM, cmd, pdMS_TO_TICKS(100));
vTaskDelay(pdMS_TO_TICKS(10)); // Wait for slave to process
Flash Workflow
Flash Both Controllers
# Flash main controller first
make robocar-flash-main PORT=/dev/cu.usbserial-0001
# Then flash camera (requires GPIO0 to GND)
# Connect GPIO0 to GND on ESP32-CAM
make robocar-flash-cam PORT=/dev/cu.usbserial-0002
# Disconnect GPIO0 from GND and reset
Development Cycle
For rapid iteration:
- Make code changes
- Build:
make robocar-build-all - Flash main:
make robocar-flash-main - Flash camera (GPIO0→GND):
make robocar-flash-cam - Monitor both in separate terminals
Common Synchronization Issues
Issue: Camera Not Responding
Symptoms:
- Main reports I2C timeout
- Camera not in monitor output
Debug Steps:
- Verify camera is powered and running
- Check I2C address matches
- Verify GPIO pins for I2C slave
- Check clock speed compatibility
Issue: Corrupted Data
Symptoms:
- Data received but values wrong
- Checksum failures
Debug Steps:
- Reduce I2C speed (try 100kHz)
- Add pull-up resistors
- Check for noise on long wires
- Verify endianness of multi-byte data
Issue: Timing Mismatch
Symptoms:
- Works sometimes, fails other times
- Camera not ready when main sends command
Debug Steps:
- Add handshake mechanism
- Increase timeout values
- Use interrupt-based I2C on camera
- Add ready signal GPIO
Tools and Commands
# Show system info
make robocar-info
# Check environment
make check-environment
# Clean and rebuild
make robocar-clean
make robocar-build-all
# Full dev cycle for main
make robocar-develop-main PORT=/dev/xxx
# Full dev cycle for camera
make robocar-develop-cam PORT=/dev/xxx