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FM Basis X - PCB

The FM Basis X PCB is plugged onto the smoke detector. A 6-pin header connects the PCB to the smoke detector.

PCB Images

  • RF Transceiver

    RF Transceiver
    Texas Instruments CC1101 with 26 MHz crystal and antenna frontend

  • Push button

    Push button
    Push button for regular functions like line test, commissioning and others

  • RF Section, EEPROM and pin header

    RF Section, EEPROM and pin header
    RF transceiver and antenna area, serial EEPROM and 6-pin header (board-to-board connector to smoke detector)

  • RF Transceiver & pin header signals

    RF Transceiver & pin header
    Pin and signal names for CC1101 and the 6-pin board-to-board connector

  • Microcontroller

    Microcontroller
    Texas instruments MSP430 low-power microcontroller with decoupling capacitors and crystal

  • Microcontroller & EEPROM signals

    Microcontroller & EEPROM signals
    Most relevant pin and signal names for MCU, EEPROM and interconnection (SPI, UART)

  • JTAG Connection

    JTAG Connection
    SMD and TH pads with JTAG signals for programming

  • JTAG Signals

    JTAG Signals
    JTAG related signal names and pin assignments

Components

Microcontroller

The PCB is equipped with a Texas Instruments MSP430F2272 ultra-low-power microcontroller.

MSP430F2272

Key features

Feature Specification
Frequency 16 MHz
Flash Memory 32KB + 256B
RAM 1KB
Supply Voltage 1.8V - 3.6V
Active Power 270 µA @ 1MHz
Standby Power 0.7 µA
Off Mode 0.1 µA
Wake-up Time < 1 µs
Package 40-pin VQFN

JTAG Access Limitation

The microcontroller offers a JTAG interface for programming and debugging.

Unfortunately I could not access the microcontroller via JTAG connection. Very likely the JTAG fuse was blown after flashing the device by the manufacturer.

RF Transceiver

The PCB is equipped with a Texas Instruments CC1101 low-power Sub-1 GHz wireless transceiver.

CC1101

Key features

Feature Specification
Protocols Proprietary, Wireless M-Bus
Modulation scheme (G)MSK, 2(G)FSK, 4(G)FSK, ASK, OOK
Frequency bands 300-348, 387-464, 779-928 MHz
TX power (max) 12 dBm
Sensitivity (best) -116 dBm
RX current (lowest) 14.3 mA
Data rate (max) 0.6 Mbps
Package 20-pin VQFN

RF Configuration Details

The specific CC1101 configuration for the Genius Plus X smoke detector network are described under FM Basis X - RF.

EEPROM

The PCB is equipped with a STMicroelectronics M95512 512 Kbit SPI bus EEPROM.

STMicroelectronics M95512

Key features

Feature Specification
Interface SPI bus compatible
Memory array 512-Kbit (64-Kbyte)
Page size 128 bytes
Write time Byte/Page Write within 5 ms
Write protect quarter array, half array, whole memory array
High-speed clock 16 MHz
Write cycles more than 4 million
Data retention more than 200-year
Package 8-pin TSSOP8

Board-to-board connection

The PCB is equipped with a standard 6-pin header (2x3) through which the connection to the smoke detector is established.

6-pin Header

Pin-# Purpose
1 GND
Ground
2 3V3
3.3 VDC power supply
3 UART-RX
Receive signal line (Radio module ← Smoke detector)
4 UART-TX
Transmit signal line (Radio module → Smoke detector)
5 Unknown
This line is connected to MSP430's pin no. 8, which is a multipurpose pin (GPIO, Analog Input, Timer related function). Its exact function is unknown, but it may possibly be used to signal a fire alarm to the radio module (in addition to or instead of via UART).
6 N.C.
No connection could be found.