Project Description
I need a compact acquisition board that reads pressure sensors and sends data by Bluetooth and Celullar (SIM). Your job covers both the hardware and the embedded layer that will live on the board.
System Requirements :
A custom PCB (embedded system) must be designed to interface with the sensor. The system will be powered by an external battery, for which voltage and current requirements must be carefully calculated.
The PCB will receive pressure data from the sensor through front-end components directly connected to the electrode outputs. A microcontroller (MCU) will scan the matrix at high frequency by sequentially energizing one electrode (e.g., rows) and measuring responses across perpendicular electrodes (e.g., columns). This scanning process allows detection of pressure points across the grid. A target scanning frequency of up to 20 MHz is considered. The velostat supplier provides a datasheet defining the relationship between applied pressure and measured voltage.
Connectivity and Data Transmission :
The system must support both Bluetooth and SIM-based communication:
• Bluetooth will be used for initial setup and when a nearby device is available.
• SIM communication will be used as a fallback when Bluetooth is unavailable, though it consumes significantly more power.
To optimize energy usage, data may be buffered locally and transmitted in batches via SIM instead of continuously.
The device should automatically power on when actual usage is detected. It must distinguish between meaningful pressure (e.g., user interaction) and irrelevant pressure (e.g., when stored in a bag).
During first use, the user connects via Bluetooth through a mobile app, which links the device to their account. Afterward:
• If Bluetooth is available, data is transmitted via Bluetooth.
• If not, data is transmitted via SIM.
The system must also ensure proper ownership handling. For example, if the device is resold, data must no longer be sent to the previous user.
Additional Obligatory Features :
• Integration of RF components to ensure reliable communication with nearby modules.
• Support for additional sensors (e.g., traction or weight sensors), including assistance in their development and integration.
• Geolocation capability accessible through the mobile application.
• Automatic detection of the number of electrods/outputs is needed. The acquisition should board should be able to get up 30x30 or 40x40 sensor’s outputs, then adapt automatically the information to be send so the device show the right matrix of pressure.
• Remote device management via an admin platform, including:
• Firmware updates (OTA)
• Remote activation/deactivation (e.g., in case of theft)
Software and Hardware Constraints :
The embedded software must be robust and support remote updates and configuration changes.
Component options such as the ESP32 may be considered, subject to validation of performance and durability.
The PCB (excluding the battery) must not exceed dimensions of 8 × 5 cm (outside the battery).