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Multiflexmeter 3.7.0

FAQ

Frequently Asked Questions

Section titled “Frequently Asked Questions”

Answers to common questions about Multiflexmeter 3.7.0.

General Questions

Section titled “General Questions”

What is Multiflexmeter?

Section titled “What is Multiflexmeter?”

Multiflexmeter 3.7.0 is an open-source IoT sensor platform based on ATmega1284P microcontroller and RFM95 LoRa radio. It’s designed for low-power, long-range sensor data collection using LoRaWAN networks.

What sensors are supported?

Section titled “What sensors are supported?”

The device supports SMBus/I²C sensors at address 0x36. It can read 8 channels of 16-bit signed integer data per measurement cycle. The specific sensor type depends on your application.

Is it compatible with The Things Network?

Section titled “Is it compatible with The Things Network?”

Yes! The device is fully compatible with TTN (The Things Network) using LoRaWAN 1.0.x OTAA activation.

What programming language is it written in?

Section titled “What programming language is it written in?”

The firmware is written in C++ with Arduino framework, built using PlatformIO. It is NOT a Python project.

Is it open source?

Section titled “Is it open source?”

Yes, both hardware and firmware are open source under MIT License.

Hardware Questions

Section titled “Hardware Questions”

What microcontroller does it use?

Section titled “What microcontroller does it use?”

ATmega1284P:

  • 128KB Flash
  • 16KB SRAM
  • 4KB EEPROM
  • 16MHz clock

What is the range?

Section titled “What is the range?”

Typical LoRaWAN range:

  • Urban: 2-5 km
  • Suburban: 5-10 km
  • Rural: Up to 15 km
  • Line-of-sight: Up to 20 km

Actual range depends on spreading factor, antenna, obstacles, and gateway sensitivity.

What is the power consumption?

Section titled “What is the power consumption?”

Typical power consumption:

  • Sleep: <1 mA
  • Active: ~10 mA
  • TX (max power): ~120 mA
  • Average (5 min interval): ~0.5-1 mA

Battery life with 10Ah battery: 1-2 years

Can I use solar power?

Section titled “Can I use solar power?”

Yes! A 5-10W solar panel with 10Ah battery is sufficient for most deployments.

What antenna should I use?

Section titled “What antenna should I use?”

Recommended:

  • Type: RP-SMA omnidirectional
  • Gain: 3dBi (standard) or 5dBi (longer range)
  • Frequency: 868MHz (EU) or 915MHz (US)
  • Mounting: Vertical orientation

Software Questions

Section titled “Software Questions”

What is PlatformIO?

Section titled “What is PlatformIO?”

PlatformIO is a professional build system for embedded development. It manages dependencies, compiles code, and uploads firmware.

Do I need Arduino IDE?

Section titled “Do I need Arduino IDE?”

No! PlatformIO works with VS Code, CLion, or command line. Arduino IDE is not required.

Can I use Arduino libraries?

Section titled “Can I use Arduino libraries?”

Yes, PlatformIO uses Arduino framework. Most Arduino libraries are compatible.

What LoRaWAN library is used?

Section titled “What LoRaWAN library is used?”

MCCI Arduino LoRaWAN Library (LMIC) version 0.9.2 or compatible.

How do I update the firmware?

Section titled “How do I update the firmware?”
Terminal window
# Build new firmware
pio run


# Upload via ISP
pio run --target upload

Configuration Questions

Section titled “Configuration Questions”

How do I configure LoRaWAN credentials?

Section titled “How do I configure LoRaWAN credentials?”

Write credentials to EEPROM:

  1. Register device on TTN
  2. Copy AppEUI, DevEUI, AppKey
  3. Generate EEPROM binary with Python script
  4. Upload with avrdude

See: Configuration Guide

What is the measurement interval?

Section titled “What is the measurement interval?”

Configurable from 20 seconds to 4270 seconds (~71 minutes).

Note: Interval is in SECONDS, not hours!

Can I change interval remotely?

Section titled “Can I change interval remotely?”

Yes, via LoRaWAN downlink on FPort 1:

Command: 0x0010
Value: 0x012C (300 seconds)
Payload: 00 10 01 2C

What are the fuse settings?

Section titled “What are the fuse settings?”
Low fuse:  0xFF
High fuse: 0xD1
Ext fuse:  0xFF

Set with: pio run --target fuses

LoRaWAN Questions

Section titled “LoRaWAN Questions”

What is OTAA?

Section titled “What is OTAA?”

Over-The-Air Activation. The device joins the network dynamically using AppEUI, DevEUI, and AppKey. More secure than ABP.

What is spreading factor?

Section titled “What is spreading factor?”

SF determines data rate vs range trade-off:

  • SF7: Fast, short range (~2km)
  • SF9: Medium speed, medium range (~5km)
  • SF12: Slow, long range (~15km)

Device uses ADR (Adaptive Data Rate) by default.

What is Fair Use Policy?

Section titled “What is Fair Use Policy?”

TTN free tier limits:

  • 30 seconds uplink airtime per day
  • 10 downlinks per device per day

Enable in EEPROM to enforce compliance.

How many messages can I send per day?

Section titled “How many messages can I send per day?”

Depends on spreading factor:

SFAirtime/msgMax messages/day (30s limit)
SF7~60ms~500
SF9~200ms~150
SF12~1.3s~23

What are FPorts used for?

Section titled “What are FPorts used for?”
  • FPort 1: Sensor measurements (16 bytes)
  • FPort 2: Firmware version (2 bytes)

Deployment Questions

Section titled “Deployment Questions”

What enclosure rating do I need?

Section titled “What enclosure rating do I need?”

Minimum IP65 (dust-tight, water jet resistant). IP67 or IP68 recommended for outdoor use.

How high should I mount the device?

Section titled “How high should I mount the device?”

Recommended: 2-5 meters

  • High enough for good signal
  • Low enough for maintenance access
  • Out of reach of tampering

How do I check gateway coverage?

Section titled “How do I check gateway coverage?”
  1. Use TTN Mapper: https://ttnmapper.org/
  2. Check TTN Console for nearby gateways
  3. Perform site survey with test device

What temperature range is supported?

Section titled “What temperature range is supported?”

Operating: -20°C to +60°C

For extreme temperatures:

  • Use insulation
  • Avoid direct sunlight
  • Consider temperature-compensated components

Troubleshooting Questions

Section titled “Troubleshooting Questions”

Device won’t join TTN, what do I check?

Section titled “Device won’t join TTN, what do I check?”
  1. Verify credentials match TTN Console exactly
  2. Check byte order (MSB first)
  3. Verify frequency plan (CFG_eu868)
  4. Check gateway coverage
  5. Enable serial debug output

See: Common Issues

How do I enable debug output?

Section titled “How do I enable debug output?”

Add to platformio.ini:

build_flags =
    -DDEBUG=1
    -DSERIAL_BAUD=115200

Connect serial console at 115200 baud.

Sensor returns all zeros?

Section titled “Sensor returns all zeros?”
  1. Check sensor power
  2. Verify I²C address (0x36)
  3. Check pullup resistors (4.7kΩ)
  4. Test with I²C scanner
  5. Verify cable connections

Upload fails with avrdude error?

Section titled “Upload fails with avrdude error?”
  1. Check ISP connections
  2. Slow down SCK clock (-B100)
  3. Verify power supply (5V)
  4. Try different programmer
  5. Check fuse settings

Development Questions

Section titled “Development Questions”

How do I add a new sensor?

Section titled “How do I add a new sensor?”
  1. Define sensor commands in sensors.h
  2. Implement driver in sensors.cpp
  3. Update measurement loop in main.cpp
  4. Modify payload format if needed

See: Development Guide

Can I add more measurement channels?

Section titled “Can I add more measurement channels?”

Yes, but limited by:

  • LoRaWAN payload size (max 51 bytes)
  • Fair Use Policy (airtime increases)
  • Memory constraints (SRAM)
Section titled “How do I add downlink commands?”
  1. Define command code
  2. Add handler in onEvent() → EV_TXCOMPLETE
  3. Update payload decoder in TTN
  4. Document in protocol specification

Can I use a different microcontroller?

Section titled “Can I use a different microcontroller?”

Yes, with porting effort:

  1. Create new board config in include/board_config/
  2. Implement board functions in src/boards/
  3. Update platformio.ini
  4. Test thoroughly

Performance Questions

Section titled “Performance Questions”

What is the maximum message rate?

Section titled “What is the maximum message rate?”

Limited by:

  • Fair Use: ~500 messages/day (SF7)
  • Duty Cycle: 1% (EU868) = ~36s/hour
  • Minimum Interval: 20 seconds

Recommended: 2-5 minute intervals for SF7

Can I reduce power consumption?

Section titled “Can I reduce power consumption?”

Yes:

  1. Enable sleep mode
  2. Reduce TX power (if close to gateway)
  3. Increase measurement interval
  4. Power off peripherals between readings
  5. Use lower spreading factor

How accurate is the timing?

Section titled “How accurate is the timing?”

Timing is based on:

  • 16MHz crystal oscillator
  • LoRaWAN network time
  • Job scheduler precision

Accuracy: ±50 ppm (crystal tolerance)

Support Questions

Section titled “Support Questions”

Where can I get help?

Section titled “Where can I get help?”
  1. Read this documentation
  2. Check Common Issues
  3. Enable debug output and analyze logs
  4. Open GitHub issue with details
  5. Contact maintainers

How do I report a bug?

Section titled “How do I report a bug?”
  1. Check if already reported (GitHub issues)
  2. Provide firmware version
  3. Include serial debug output
  4. Describe steps to reproduce
  5. Mention expected vs actual behavior

Can I contribute?

Section titled “Can I contribute?”

Yes! Contributions welcome:

  1. Fork repository
  2. Create feature branch
  3. Make changes
  4. Test thoroughly
  5. Submit pull request

Contact the project maintainers via GitHub issues for contribution opportunities.

Where is the source code?

Section titled “Where is the source code?”

GitHub: https://github.com/MrMisterMisterMister/MFM-docs

Next Steps

Section titled “Next Steps”