Cellular modem

[038] BLDC MOTOR CONTROL

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This project is all about embedded BLDC motor control on an STM32 platform. Two different approaches were explored.

The first one: driving motors over a CAN bus. That means dealing with CAN communication, command framing, coordinating several motor controllers on a shared network, and handling basic fault conditions without things falling apart.

The second approach is more involved: direct three-phase control, with a custom motor driver built to handle 200 W at 24 V and 7 A. That includes designing the MOSFET power stage, PWM generation, commutation logic, current and voltage sensing, plus overcurrent and thermal protection.

Distance sensors and IMUs were also integrated to keep the system stable on sloped or uneven surfaces. The main thread running through all of it: getting power electronics, motor control, and sensor feedback to work together as one coherent system — not just as separate blocks bolted together.

[013] EMBEDDED 4G TRACKING DEVICE

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GPS, 9-axis IMU, 4G modem with 2G fallback, BLE, Li-Ion battery — all on one compact platform built around an STM32L152.

4G is the primary communication path, with 2G taking over if coverage degrades. BLE provides a local interaction layer through a smartphone — configuration and status access without going through the cellular network. The IMU adds motion awareness on top of positioning: not just where the device is, but how it’s moving.

In a product like this, energy management is its own engineering challenge. The cellular modem, GNSS receiver, and IMU all have very different power profiles, and the whole thing has to run on battery in unpredictable field conditions. A real system architecture problem from start to finish.

[012] CUSTOM 868 MHz TO CELLULAR GATEWAY

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Connecting remote radio nodes to a distant server, with no wired infrastructure — that’s what this gateway is built for.

On one side, a 868 MHz radio interface handles links with multiple remote nodes. On the other, a cellular modem (4G primary, 2G fallback) forwards the data to the outside world. The STM32L152 supervises communication, power management, and overall system behavior.

Power comes from a battery combined with a solar panel, which means energy management is directly tied to communication strategy. In standby, you conserve. When it’s time to transmit, you spend. Finding the right balance between those two modes in real field conditions — that’s where the design actually gets interesting.