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
Schematic Capture Status — MCU / USB / Modems
Completed in schematic
Added these main components:
- U5: STM32H757ZIY6TR MCU.
- J2: USB-C 2.0 service/programming connector.
- D2: USBLC6-2SC6 ESD protection for USB D+/D-.
- J3: 10-pin ARM SWD debug/programming connector.
- U6/U7: Quectel-compatible EC25 module symbols used as placeholders for the required EC21-AUV / approved Quectel variant.
- R21/R6: USB-C CC pull-downs.
- R7/R8: STM32 BOOT0 pull-down and NRST pull-up.
- C20/C6/C7: STM32 VCAP capacitors.
- C8: NRST filter capacitor.
- C9/C10/C21-C24: initial 3.3 V decoupling capacitors.
STM32 core wiring completed
- Main VDD/VDDLDO/VBAT/VDDA/VREF+/VDD33USB tied to 3V3_SYS.
- VSS/VSSA tied to GND.
- VCAP pins connected to local capacitors to GND.
- BOOT0 pulled down for normal boot.
- NRST pulled up with reset capacitor and connected to SWD header.
- DSI pins marked no-connect for now.
USB-C service wiring completed
- USB-C VBUS connected to USB_VBUS and STM32 VBUS-sense/USB supply pins used in this first pass.
- USB-C CC1/CC2 each has a 5.1 kΩ pull-down to GND for device-mode behavior.
- USB D+/D- routed through the ESD array to STM32 PA12/PA11.
- SBU pins marked no-connect.
SWD wiring completed
- SWDIO to STM32 PA13.
- SWCLK to STM32 PA14.
- SWO to STM32 PB3.
- NRST to STM32 NRST.
- VTref to 3V3_SYS.
- Grounds connected.
Dual modem wiring completed
- U6 modem powered from 4V0_MODEM_A.
- U7 modem powered from 4V0_MODEM_B.
- Modem grounds connected.
- UART + hardware flow-control nets connected to STM32:
- Modem A: TX/RX/RTS/CTS to PA3/PA2/PA1/PA0.
- Modem B: TX/RX/RTS/CTS to PB11/PB10/PB13/PB12.
- PWRKEY, RESET_N, STATUS, and RI signals connected from each modem to STM32 GPIOs.
- RF main antenna nets created: RF_MODEM_A_MAIN and RF_MODEM_B_MAIN.
Important caveats
- U6/U7 are EC25 library symbols used as EC21-compatible placeholders. Replace with exact EC21-AUV / final approved module before release.
- SIM sockets, SIM ESD, external antenna connectors, RF ESD, and RF matching/keepout details are not added yet.
- STM32H757 power scheme needs a datasheet-level audit before finalizing: SMPS-related pins and USB supply configuration must be verified.
- Per-pin STM32 decoupling is not complete yet; current capacitors are first-pass placeholders.
- ERC still reports many expected floating GPIO/module pins because downstream blocks are not connected yet.
Next schematic step
Add the two SIM slots, RF/u.FL antenna connectors with ESD protection, and modem support passives, then move to the eight sealed resistor-pack inputs.
Completed in schematic
STM32 core wiring completed
USB-C service wiring completed
SWD wiring completed
Dual modem wiring completed
Important caveats
Next schematic step
