Pressure Sensor

Goal

To implement safety use cases in our door project, we use a pressure sensor to detect whether an obstacle keeps the door from closing.

There are a number of sensors out there. BMP280 comes with a nice breakout, it looks like a good candidate to try.

How

I2C devices speak a protocol over SDA/SCL which is documented in the device’s data sheet. Lets use /dev/i2c-1 (a software representation of Raspberry’s I2C pins) to implement that protocol in userspace - inside a class which looks roughly like so …

class BMP280
{
public:
    BMP280(const std::string& i2c_dev, unsigned address);
};

  • i2c_dev: the I2C device node, e.g. /dev/i2c-1

  • address: the device’s address on the bus

Testing

This is not easily unit tested. Write a test program in tests/ that uses an object of type BMP280 to communicate with the device.