GSM / 4G Telemetry Link
Bring up a cellular modem, verify registration and send minimal telemetry with robust power handling.
Topology and objective
MCU UART → cellular modem → mobile network → HTTPS/MQTT endpoint.
Hardware and tools
- Supported development board
- USB data cable
- Current-limited supply
- Serial monitor and logic analyser when applicable
Security and RF safety
- Observe SIM and carrier terms.nDo not expose IMEI, IMSI or phone number publicly.nKeep antenna clear and use approved RF hardware.
Practical procedure
- Power modem from a supply rated for current bursts.nTest AT response and SIM status.nCheck network registration and signal quality.nAttach packet data with test APN.nSend one authenticated telemetry message and disconnect cleanly.
Telemetry / payload
ATnAT+CPIN?nAT+CREG?nAT+CSQStarter code / config
Use modem-specific HTTPS/MQTT commands and placeholders for APN credentials.Expected results
| Checkpoint | Expected | Tool |
|---|---|---|
| Registration | Registered home/roaming status | SerialnData |
Troubleshooting
| Symptom | Check | Action |
|---|---|---|
| Modem resets | Measure supply during transmit burst | Improve supply and bulk capacitancenNo network |
Local-only sandbox
Commands & telemetry simulator
Send command
Simulator ready. No network connection is used.