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Smart Cities Group Project

SIM7080G – Hardware Guide

This page documents how the SIMCom SIM7080G cellular module is powered, connected, and validated in this project. It complements the datasheet and hardware design resources from the vendor:

  • Product page: https://www.simcom.com/product/SIM7080G.html
  • Reference manuals and AT command set: see downloads on the product page.

The SIM7080G is a low‑power LTE Cat‑M1/NB‑IoT + GNSS module. In this project it is mounted on a board with an AXP2101 PMU and is controlled by an ESP32.

Module capabilities (project-relevant)

  • LTE Cat‑M1 and NB‑IoT with global bands (board/SIM dependent).
  • Packet data over IP (APN required).
  • TCP/UDP/HTTP(S) stacks on-module.
  • GNSS (GPS/GLONASS/BeiDou/Galileo/QZSS) with active antenna power rail available on the board.
  • Diagnostic AT commands for registration, signal, bearer activation, and ping.

Hardware integration

Power tree (AXP2101 PMU)

The PMU powers the modem and GNSS rails. The firmware configures:

  • DC3 = 3.0 V → main SIM7080G supply (per project code).
  • BLDO2 = 3.3 V → GNSS antenna bias (enable for GNSS use).
  • TS pin measurement disabled to allow battery charging.

These settings are applied in code:

  • DC3 enabled at 3.0 V.
  • BLDO2 enabled at 3.3 V.
  • T_SENSE measurement disabled.

Notes:

  • Ensure the 3.0 V rail can supply modem peaks (hundreds of mA during Tx bursts).
  • Keep supply decoupling capacitors close to the module as per SIMCom hardware design guide.
  • Use a good ground plane; minimize supply and RF return path impedance.

ESP32 connections (typical)

  • UART: ESP32 Serial1 (TXD/RXD) → SIM7080G UART0 (115200 8N1).
  • PWRKEY: GPIO → controls modem power-on sequence (low pulse >1 s).
  • DTR: GPIO → sleep control (optional; keep defined).
  • RI: GPIO input → ring indicator (optional).
  • I2C: SDA/SCL → AXP2101 PMU control.
  • GNSS antenna power: provided by BLDO2 (3.3 V) on the board (enable only when needed).

Exact pin numbers are board-specific. See your board header/pinmap for:

  • BOARD_MODEM_TXD_PIN / BOARD_MODEM_RXD_PIN
  • BOARD_MODEM_PWR_PIN / BOARD_MODEM_DTR_PIN / BOARD_MODEM_RI_PIN
  • I2C_SDA / I2C_SCL

Antennas

  • Main LTE antenna: required for cellular connectivity.
  • GNSS antenna: required for GNSS; enable BLDO2 to power active antennas.
  • Keep antenna connectors tight; route coax away from noisy digital lines.

SIM card

  • Use a Cat‑M1/NB‑IoT capable SIM (e.g., 1NCE).
  • APN must be set (project uses APN: iot.1nce.net).
  • Verify SIM presence with AT+CPIN? and TinyGSM getSimStatus().

Power‑on and bring‑up sequence

  1. PMU init:

    • Initialize AXP2101 over I2C.
    • Disable TS pin measurement.
    • Enable DC3 (3.0 V) for modem.
    • Enable BLDO2 (3.3 V) only if GNSS is needed.

  2. Modem start:

    • Configure UART (115200 8N1).
    • Pulse PWRKEY: low >1 s to boot the module.
    • Wait for AT responsiveness (test with AT).

  3. Network setup:

    • CFUN=0 (RF off), set network and preferred mode (Cat‑M1 by default).
    • Set APN with CGDCONT.
    • CFUN=1 (RF on), wait for registration (home or roaming).
    • Configure PDP profile with CNCFG, then activate with CNACT=0,1.
    • Optionally enable local time sync CLTS and read CCLK.

These steps are automated by SIM7080::initialize(), ::start(), ::setupNetwork().

Software dependencies (project)

  • TinyGSM (SIM7080 profile): UART/AT management and helpers.
  • XPowersLib (AXP2101): PMU control for rails and charging.
  • Arduino framework on ESP32.

Validation and diagnostics

Use these checks to validate hardware wiring and the RF path:

  • Modem alive:
    • AT → OK
  • SIM ready:
    • AT+CPIN? → READY
  • Registration:
    • AT+CEREG? (LTE attach), AT+CGREG? or AT+CREG? → registered (home/roaming)
  • Operator and RAT:
    • AT+COPS? → operator, RAT (Cat‑M1/NB)
  • Signal quality:
    • AT+CSQ → RSSI BER (e.g., 10–20 typical indoors on Cat‑M1)
  • PDP/bearer:
    • AT+CNACT? → state 1 when active, show IP address
  • Ping:
    • AT+SNPING4="8.8.8.8",1,3000,32 → verify IP reachability

The project emits structured logs during these steps. Use the serial monitor at 115200 baud.

Project criteria mapping

  • “The CMB can connect to the internet using an LTE network.”

    • Achieved by SIM7080::setupNetwork() (APN, registration, bearer activation). Requires antenna and coverage.

  • “The SIM7080G module can ping 8.8.8.8.”

    • Supported via AT+SNPING4. Add a small helper in code or issue the command from a debug console after CNACT=0,1.

  • “The connection automatically re‑establishes after loss of signal or restart.”

    • Use SIM7080::ensureConnected() periodically. It re‑runs setup when GPRS/bearer is down.

  • “The connection status is visible or logged for diagnostics.”

    • Logs include SIM status, registration, bearer state, HTTPS transactions. Add periodic CSQ/CNACT logging if needed.

  • “Documentation is created on the relevant page.”

    • This page provides the hardware overview, wiring, bring‑up, and validation steps.

Quick test procedure

  1. Power and boot:

    • Observe “Power chip initialized” and “Modem started” on serial logs.

  2. SIM and registration:

    • Check “Registered, home network” or “Registered, roaming”.
    • If it times out, verify antenna/SIM and coverage.

  3. Bearer activation:

    • Confirm “GPRS status: connected” and CNACT? returns an IP.

  4. Ping test (optional):

    • Send AT+SNPING4="8.8.8.8",1,3000,32
    • Expect a response line “+SNPING4:…” with RTT and success.

  5. HTTPS test:

    • The sample app posts JSON to the configured server.
    • Check SHCONN/SHREQ logs and server-side receipt.

    A. Data queueing - Shut down the docker container or disconnect the antenna. - Observe “Failed to post data” logs and data being queued.

    B. Recovery - Restore connectivity. - Observe queued data being sent successfully.

Troubleshooting

  • No AT responses:
    • Check UART wiring, baud rate, PWRKEY timing, PMU rails (DC3 enabled at 3.0 V).
  • Not registered:
    • Verify SIM/APN, antenna, coverage for Cat‑M1/NB‑IoT. Try alternative RAT (NB) or band scan.
  • Bearer won’t activate:
    • Recheck APN (CGDCONT + CNCFG), ensure CFUN=1 and module registered. Power cycle if needed.
  • Weak signal:
    • Check CSQ; improve antenna placement, use proper ground clearance, move outdoors.
  • HTTPS failures:
    • Verify time sync (CLTS/CCLK), SNI configuration, and server TLS compatibility.

Safety and RF notes

  • Keep antennas away from users or sensitive analog circuits during Tx.
  • Follow local regulations for LTE/NB‑IoT operation and bands.
  • Use ESD precautions when handling RF connectors.

References

  • SIM7080G Product page and downloads: https://www.simcom.com/product/SIM7080G.html
  • SIMCom SIM7080 Series AT Command Manual (from product page)
  • SIMCom Hardware Design Guide for SIM7080 series
  • TinyGSM library docs (SIM7080 profile)