Skip to content
Multiflexmeter

Hardware Specifications

Complete technical specifications for the Multiflexmeter 3.7.0 hardware platform.

Microcontroller

Section titled “Microcontroller”

MFM V3 M1284P (Primary/Current)

Section titled “MFM V3 M1284P (Primary/Current)”
SpecificationValue
ModelATmega1284P
Architecture8-bit AVR RISC
Clock Speed8 MHz (internal oscillator)
Flash Memory128 KB
SRAM16 KB
EEPROM4 KB
I/O Pins32 programmable
Operating Voltage1.8V - 5.5V
Typical Operating3.3V - 5V
Arduino CoreMightyCore

MFM V3 (Legacy)

Section titled “MFM V3 (Legacy)”
SpecificationValue
ModelATmega328P
Architecture8-bit AVR RISC
Clock Speed8 MHz (internal oscillator)
Flash Memory32 KB
SRAM2 KB
EEPROM1 KB
I/O Pins23 programmable
Operating Voltage1.8V - 5.5V
Typical Operating3.3V - 5V
Arduino CoreMiniCore

LoRa Radio Module

Section titled “LoRa Radio Module”
SpecificationValue
ModelHopeRF RFM95W
Frequency868 MHz (EU band)
ModulationLoRa, FSK, GFSK, MSK, OOK
TX Power+20 dBm (100mW) max
RX Sensitivity-148 dBm (SF12, 125kHz)
InterfaceSPI
RangeUp to 10 km line-of-sight

Power Specifications

Section titled “Power Specifications”
ParameterConditionTypicalMaximumUnit
Supply VoltageOperating3.3 - 5.0-V
Sleep CurrentDeep sleep< 15mA
Active CurrentMeasuring2030mA
TX Current+20dBm, 868MHz120150mA
RX CurrentReceiving1015mA

Sensor Interface

Section titled “Sensor Interface”
SpecificationValue
ProtocolSMBus / I²C
Bus Speed80 kHz (configured in firmware)
Voltage Level3.3V or 5V (depending on supply)
Pull-up Resistors4.7kΩ on SDA and SCL
Default Sensor Address0x36

Programming Interfaces

Section titled “Programming Interfaces”

ISP (In-System Programming)

Section titled “ISP (In-System Programming)”
PinFunction
1MISO
2VCC
3SCK
4MOSI
5RESET
6GND

Compatible Programmers:

  • USBasp
  • AVRISP mkII
  • Atmel-ICE
  • Arduino as ISP

UART Debug Header

Section titled “UART Debug Header”
PinFunction
1GND
2CTS (not used)
3VCC (3.3V/5V output)
4TX (MCU transmit)
5RX (MCU receive)
6RTS (not used)

Settings:

  • Baud Rate: 115200
  • Data Bits: 8
  • Parity: None
  • Stop Bits: 1
  • Flow Control: None

Pin Assignments

Section titled “Pin Assignments”

See Pin Mappings for complete pin assignments.

Fuse Settings

Section titled “Fuse Settings”
FuseValueDescription
Low Fuse0xFFExternal crystal oscillator, fast start-up
High Fuse0xD1SPI enabled, BOD 2.7V, EESAVE enabled
Extended Fuse0xFFBOD enabled

Critical Fuse Bits:

  • SPIEN: Enabled (allows ISP programming)
  • BOOTRST: Application reset (not bootloader)
  • EESAVE: EEPROM preserved during chip erase
  • BODLEVEL: 2.7V (prevents brownout issues)

Environmental Specifications

Section titled “Environmental Specifications”
ParameterMinimumTypicalMaximumUnit
Operating Temperature-2025+70°C
Storage Temperature-40-+85°C
Humidity0-95% RH (non-condensing)

Mechanical Specifications

Section titled “Mechanical Specifications”
ParameterValue
PCB DimensionsTBD × TBD mm
Mounting4× M3 holes
Antenna ConnectorSMA or U.FL
EnclosureOptional weatherproof case

Board Variants

Section titled “Board Variants”
Section titled “MFM V3 M1284P (Recommended)”
  • Board ID: mfm_v3_m1284p
  • MCU: ATmega1284P
  • Memory: 128KB Flash, 16KB RAM, 4KB EEPROM
  • Clock: 8MHz internal oscillator
  • Arduino Core: MightyCore
  • Features: Full feature set, production-ready
  • Upload Protocol: stk500 at 115200 baud
  • Status: Current/active variant

MFM V3 (Legacy)

Section titled “MFM V3 (Legacy)”
  • Board ID: mfm_v3
  • MCU: ATmega328P
  • Memory: 32KB Flash, 2KB RAM, 1KB EEPROM
  • Clock: 8MHz internal oscillator
  • Arduino Core: MiniCore
  • Features: Reduced I/O pins, limited memory
  • Upload Protocol: stk500v2 at 115200 baud
  • Status: Legacy support only

Compliance

Section titled “Compliance”
StandardStatus
CEDesign compliant (requires testing)
LoRaWAN 1.0.xCertified via LMIC library
ETSI EN 300 220EU 868MHz compliance
RoHSCompliant components

Performance Characteristics

Section titled “Performance Characteristics”

Battery Life Estimates

Section titled “Battery Life Estimates”

Assuming 3× AA alkaline batteries (~3000 mAh @ 4.5V):

IntervalEst. Battery Life
15 min (900s)9-12 months
30 min (1800s)12-18 months
1 hour (3600s)18-24 months

Factors affecting battery life:

  • Measurement interval
  • Spreading factor (SF7 vs SF12)
  • Sensor power consumption
  • Temperature
  • Number of join attempts

LoRaWAN Performance

Section titled “LoRaWAN Performance”
Spreading FactorData RateAirtime (24 bytes)RangeBattery Impact
SF75470 bps~61 ms2 kmLowest
SF83125 bps~113 ms3 kmLow
SF91760 bps~206 ms4 kmMedium
SF10980 bps~371 ms6 kmMedium-High
SF11440 bps~741 ms8 kmHigh
SF12250 bps~1483 ms10+ kmHighest

Bill of Materials

Section titled “Bill of Materials”

Key components:

  • ATmega1284P-AU (TQFP-44)
  • RFM95W-868S2 (LoRa module)
  • 16 MHz crystal
  • Voltage regulator (3.3V or 5V)
  • Passive components (resistors, capacitors)
  • Headers (ISP, UART, sensor)
  • Antenna (868MHz)

Full BOM available in KiCad project files.

Design Files

Section titled “Design Files”
  • Schematics: Available in hardware/ directory
  • PCB Layout: KiCad PCB file
  • Gerber Files: For manufacturing
  • 3D Models: STEP files for enclosure design

Certifications & Testing

Section titled “Certifications & Testing”

Required Testing for Deployment

Section titled “Required Testing for Deployment”
  1. RF Performance: Range, sensitivity, interference
  2. Environmental: Temperature, humidity cycling
  3. EMC: Emissions and immunity
  4. Mechanical: Vibration, shock (if applicable)
  5. Long-term: Battery life validation

Regional Variants

Section titled “Regional Variants”

For operation outside EU868:

  • US915: Requires firmware modification
  • AS923: Requires firmware modification
  • AU915: Requires firmware modification

Contact maintainers for regional variants.

Next Steps

Section titled “Next Steps”

Legacy Documentation

Section titled “Legacy Documentation”

MFM v2.0 Hardware Specification (Reference)

Section titled “MFM v2.0 Hardware Specification (Reference)”

📄 Download Hardware Specification (PDF)