Case study
Low-power float tracker
A compact ESP32 tracker for a remote float: the ULP coprocessor wakes the board, a GPS gives position, and a GSM modem sends the update by SMS.
ULP wake → GPS → GSM SMS
- Record
- Described in my project notes. No public repository. No client name.
- Stack
- ESP32, ULP, GPS, GSM
- Hardware
- ESP32 · ULP coprocessor · RTC · GPS · GSM modem
The problem
A float sitting offshore cannot rely on Wi-Fi, and it cannot wake a full ESP32 every few minutes if the battery has to last. The position still has to leave the device.
What I built
A compact tracker on ESP32. The ULP coprocessor, written in assembly, handles the periodic wake and the sensor check so the main CPU stays asleep. An RTC keeps the schedule. GPS provides the location. A GSM modem sends the update as SMS, so the unit does not need an internet session.
It is built for a remote marine float: no site network, and the power budget is the constraint.
Decisions
SMS instead of a data session, because the link only has to carry a position. The ULP path exists so the radio and the main core are not the thing that drains the pack between reports.