IoT Fire Alarm Device Design
Thought for 8 sec
You should ask Quectel / supplier for the EC25MXGA hardware design package, not just the marketing datasheet.
Ask for:
-
EC25MXGA Hardware Design Guide
- Full pin descriptions
- Power supply requirements
- PWRKEY / RESET timing
- UART / USB / SIM / RF reference circuits
- VDD_SDIO usage guidance
-
Recommended PCB land pattern / footprint
- Pad dimensions
- Pad numbering
- Paste mask / solder mask recommendations
- Keepout zones under/around the module
- Assembly notes
-
Reference schematic
- VBAT_RF / VBAT_BB decoupling
- SIM socket wiring
- Antenna matching / ESD
- Status pins
- Power-on/off sequence
-
RF layout guidelines
- 50 Ω antenna routing
- Ground stitching via recommendations
- Antenna connector/matching network placement
- Diversity/GNSS pins if used or unused
-
Certification documents
- RCM / ACMA / AS/CA S042 relevance
- Carrier approval info for Australia
- LTE band support for AU carriers
- Test reports if available
-
Lifecycle / supply confirmation
- Active production status
- Recommended replacement if EC25MXGA is not preferred
- Minimum order / lead time
Short message you can send:
We are designing a dual-modem Australian fire alarm signalling device using 2 × EC25MXGA. Please provide the EC25MXGA hardware design guide, recommended PCB land pattern/footprint, reference schematic, RF layout guide, SIM interface recommendations, VDD_SDIO connection guidance, Australian carrier/certification documentation, and lifecycle/supply status.
Ok I’ll contact them
Thought for 14 sec
Good plan. Ask them specifically for the hardware design guide + recommended PCB land pattern for EC25MXGA-128-SNNS.
Until we get that, the safest path is:
- Keep EC25MXGA in the design.
- Do not send the PCB to manufacture yet.
- Continue with placement/routing cleanup only as a draft.
- Finalize modem footprint, SIM wiring, RF layout, and
VDD_SDIOtreatment once Quectel confirms the official guidance.
Clean draft layout
Review EC25 wiring
Check power budget
Update factory checklist
Run current checks
Refine this doc
Ask about this doc
Project Specification — UL / Australian Fire Alarm IoT Signaling Device
Purpose
Design an IoT fire alarm signalling device / Alarm Signalling Equipment (ASE)-class product for fire alarm monitoring.
Current locked baseline
- Main MCU: STM32H757-class MCU, recommended STM32H757ZI family.
- Cellular: 2 × Quectel modules, both always active / hot redundant.
- SIMs: 2 × SIM slots, one per modem.
- Server polling/check-in: every 20 seconds from both modem paths.
- Antennas: 2 × external cellular antennas via PCB u.FL/IPEX connectors and pigtails to external panel connectors.
- Programming/service: USB-C device-mode programming/service port, not main power.
- Service/isolate key: Dallas/iButton-style key.
- Display: SPI LCD-style front display.
- Buttons: 4 front navigation buttons — Up, Down, Left, Right.
- Inputs: 8 supervised FAS/FDCIE inputs using a custom sealed resistor-pack architecture.
- Dedicated power-fail input: yes.
- Outputs: 3 programmable relay outputs.
- Input power: 12–24 VDC nominal, with protected front end designed to handle incorrect voltage, reverse polarity, surges/transients, and brownout.
8-input behavior target
Each of the 8 supervised inputs will use a sealed external resistor-pack / EOL module at the FDCIE side.
Each sealed resistor pack may accept voltage-free contacts for:
- Alarm
- Fault
- Isolate / Disabled
The pack converts those contact states into one supervised two-wire analog input to the ASE.
Each input should decode:
- Short circuit / line fault
- Normal
- Isolate
- Fault
- Isolate + Fault
- Alarm
- Alarm + Isolate
- Alarm + Fault
- Alarm + Fault + Isolate
- Open circuit / line fault
The exact resistor values and final voltage bands remain to be designed.
Power-fail input
A separate power-fail input is required for the FDCIE/panel power-supply failure signal. This is separate from the ASE’s own input-voltage monitoring.
3 programmable relays
The board shall include 3 firmware-programmable relay outputs. Candidate functions include alarm repeat, fault/trouble, communications fail, isolate active, test/service active, or site-specific control.
Safety and compliance assumptions
- AS4428.6 should drive ASE equipment requirements.
- AS1670.3 should drive fire alarm monitoring/network performance requirements.
- AS/CA S042 and ACMA requirements apply to the cellular subsystem.
- Cellular/radio module approvals, antenna selection, RF layout, and enclosure labeling must be tracked for compliance review.
Power architecture baseline
- Protected 12–24 VDC input terminal.
- Fuse/eFuse or hot-swap/surge-stopper controller.
- Reverse-polarity protection.
- TVS and EMI filtering.
- Over-voltage cutoff for incorrect input voltage.
- Under-voltage/brownout detection.
- Two independent ~4.0 V high-current modem rails.
- 3.3 V system logic rail.
- Power-good/fault monitoring into STM32.
Compliance-driven requirements to carry forward
- Detect and locally indicate telecommunications path loss within required standard timing.
- Support event-initiated alarm/fault/isolate/test reporting.
- Support cyclic/heartbeat reporting or equivalent communications integrity check.
- Support acknowledgement, retry, and event buffering during communications outage.
- Maintain clock/time reference suitable for timestamps and synchronization.
- Provide LCD/local indication for ALM, FLT, DIS/ISO, PWR, line fault, modem path status, and test/isolate mode.
- Provide installation/user documentation with power requirements, input/output ratings, fuse ratings, cable parameters, communication parameters, and environmental suitability.
Required decisions before schematic capture
- Confirm exact orderable MCU part number/package.
- Confirm exact Quectel module part number.
- Confirm STM32-to-Quectel interface: recommended UART per modem plus PWRKEY/RESET/STATUS GPIO.
- Confirm exact sealed resistor-pack resistor values and voltage bands.
- Confirm whether every one of the 8 inputs needs Alarm/Fault/Isolate decoding, or whether some inputs are simpler alarm-only channels.
- Confirm relay contact rating and default functions.
- Confirm LCD module/backlight requirements.
- Confirm final input protection controller and buck regulator choices.
Notes
Do not treat this document as certification evidence. It is the engineering starting point for requirements capture and schematic planning. Detailed standard clauses, resistor-pack values, and certification assumptions must be verified before production/certification work.
Purpose
Current locked baseline
8-input behavior target
Power-fail input
3 programmable relays
Safety and compliance assumptions
Power architecture baseline
Compliance-driven requirements to carry forward
Required decisions before schematic capture
Notes
