Complete technical specifications for the Multiflexmeter 3.7.0 hardware platform.
| Specification | Value |
|---|
| Model | ATmega1284P |
| Architecture | 8-bit AVR RISC |
| Clock Speed | 8 MHz (internal oscillator) |
| Flash Memory | 128 KB |
| SRAM | 16 KB |
| EEPROM | 4 KB |
| I/O Pins | 32 programmable |
| Operating Voltage | 1.8V - 5.5V |
| Typical Operating | 3.3V - 5V |
| Arduino Core | MightyCore |
| Specification | Value |
|---|
| Model | ATmega328P |
| Architecture | 8-bit AVR RISC |
| Clock Speed | 8 MHz (internal oscillator) |
| Flash Memory | 32 KB |
| SRAM | 2 KB |
| EEPROM | 1 KB |
| I/O Pins | 23 programmable |
| Operating Voltage | 1.8V - 5.5V |
| Typical Operating | 3.3V - 5V |
| Arduino Core | MiniCore |
| Specification | Value |
|---|
| Model | HopeRF RFM95W |
| Frequency | 868 MHz (EU band) |
| Modulation | LoRa, FSK, GFSK, MSK, OOK |
| TX Power | +20 dBm (100mW) max |
| RX Sensitivity | -148 dBm (SF12, 125kHz) |
| Interface | SPI |
| Range | Up to 10 km line-of-sight |
| Parameter | Condition | Typical | Maximum | Unit |
|---|
| Supply Voltage | Operating | 3.3 - 5.0 | - | V |
| Sleep Current | Deep sleep | < 1 | 5 | mA |
| Active Current | Measuring | 20 | 30 | mA |
| TX Current | +20dBm, 868MHz | 120 | 150 | mA |
| RX Current | Receiving | 10 | 15 | mA |
| Specification | Value |
|---|
| Protocol | SMBus / I²C |
| Bus Speed | 100 kHz (standard mode) |
| Voltage Level | 3.3V or 5V (depending on supply) |
| Pull-up Resistors | 4.7kΩ on SDA and SCL |
| Default Sensor Address | 0x36 |
| Pin | Function |
|---|
| 1 | MISO |
| 2 | VCC |
| 3 | SCK |
| 4 | MOSI |
| 5 | RESET |
| 6 | GND |
Compatible Programmers:
- USBasp
- AVRISP mkII
- Atmel-ICE
- Arduino as ISP
| Pin | Function |
|---|
| 1 | GND |
| 2 | CTS (not used) |
| 3 | VCC (3.3V/5V output) |
| 4 | TX (MCU transmit) |
| 5 | RX (MCU receive) |
| 6 | RTS (not used) |
Settings:
- Baud Rate: 115200
- Data Bits: 8
- Parity: None
- Stop Bits: 1
- Flow Control: None
See Pin Mappings for complete pin assignments.
| Fuse | Value | Description |
|---|
| Low Fuse | 0xFF | External crystal oscillator, fast start-up |
| High Fuse | 0xD1 | SPI enabled, BOD 2.7V, EESAVE enabled |
| Extended Fuse | 0xFF | BOD 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)
| Parameter | Minimum | Typical | Maximum | Unit |
|---|
| Operating Temperature | -20 | 25 | +70 | °C |
| Storage Temperature | -40 | - | +85 | °C |
| Humidity | 0 | - | 95 | % RH (non-condensing) |
| Parameter | Value |
|---|
| PCB Dimensions | TBD × TBD mm |
| Mounting | 4× M3 holes |
| Antenna Connector | SMA or U.FL |
| Enclosure | Optional weatherproof case |
- 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
- 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
| Standard | Status |
|---|
| CE | Design compliant (requires testing) |
| LoRaWAN 1.0.x | Certified via LMIC library |
| ETSI EN 300 220 | EU 868MHz compliance |
| RoHS | Compliant components |
Assuming 3× AA alkaline batteries (~3000 mAh @ 4.5V):
| Interval | Est. 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
| Spreading Factor | Data Rate | Airtime (24 bytes) | Range | Battery Impact |
|---|
| SF7 | 5470 bps | ~61 ms | 2 km | Lowest |
| SF8 | 3125 bps | ~113 ms | 3 km | Low |
| SF9 | 1760 bps | ~206 ms | 4 km | Medium |
| SF10 | 980 bps | ~371 ms | 6 km | Medium-High |
| SF11 | 440 bps | ~741 ms | 8 km | High |
| SF12 | 250 bps | ~1483 ms | 10+ km | Highest |
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.
- Schematics: Available in
hardware/ directory
- PCB Layout: KiCad PCB file
- Gerber Files: For manufacturing
- 3D Models: STEP files for enclosure design
- RF Performance: Range, sensitivity, interference
- Environmental: Temperature, humidity cycling
- EMC: Emissions and immunity
- Mechanical: Vibration, shock (if applicable)
- Long-term: Battery life validation
For operation outside EU868:
- US915: Requires firmware modification
- AS923: Requires firmware modification
- AU915: Requires firmware modification
Contact maintainers for regional variants.
📄 Download Hardware Specification (PDF)