- Use only widely available, easy to source components. Right now the design has nothing more interesting than a general purpose microcontroller (STM32F042 LQFP-32), general purpose opamps, a low side driver, and passives.
- Support Bosch LSU 4.9 sensor. The LSU 4.2 requires free air calibration, and 4.9 sensors are so widespread that there's not a good reason to support the older sensors.
- Support both in-ECU use, as well as standalone. That means SPI or serial comms with an ECU, and CAN or analog for external use.
Here's the module as it exists today:
The SD-card-sized module can run either inside an ECU, or independently when stacked on the board with the big connector. The second board just provides a power supply and CAN interface, parts that are unnecessary when inside an ECU. Everything required to run the sensor is on the tiny module.