Add support for bme68x sensor

[gandarez]

This PR adds support for BME68X (BME680/BME688) a low power gas, pressure, temperature & humidity sensor.

It includes the support for Sleep and Forced modes as well I2C and SPI interfaces. It introduces the Options Pattern to make the initialization of bme68x package more flexible.

Simple example:

tsensor := bme68x.NewI2C(machine.I2C0,
    bme68x.WithIIRFilter(bme68x.Coeff4),
    bme68x.WithTemperatureOversampling(bme68x.Sampling8X),
    bme68x.WithPressureOversampling(bme68x.Sampling4X),
    bme68x.WithHumidityOversampling(bme68x.Sampling2X),
    bme68x.WithHeatrDuration(150),
    bme68x.WithHeatrTemperature(320),
)
if err := tsensor.Configure(); err != nil {
     logger.Error(fmt.Sprintf("error configuring sensor: %s", err.Error()))
     return
}

connected, err := tsensor.Connected()
if err != nil {
    logger.Error(fmt.Sprintf("error checking sensor connection: %s", err.Error()))
    return
}

if !connected {
    logger.Error("sensor not connected")
    return
}

if err := tsensor.SetMode(bme68x.ModeForced); err != nil {
    logger.Error(fmt.Sprintf("error setting sensor mode: %s", err.Error()))
    return
}

for {
    if err := tsensor.Read(); err != nil {
        logger.Error(fmt.Sprintf("error reading sensor: %s", err.Error()))

	time.Sleep(2 * time.Second)
	continue
    }

     logger.Info(strings.Repeat("-", 40))

     logger.Info(fmt.Sprintf("    Temperature: %.2f°C", tsensor.Temperature))
     logger.Info(fmt.Sprintf("    Pressure: %.fhPa", tsensor.Pressure/100))
     logger.Info(fmt.Sprintf("    Gas: %.1fKOhms", tsensor.GasResistance/1000))
     logger.Info(fmt.Sprintf("    Approx. Altitude: %.1fm", bme68x.CalcAltitude(seaLevelPressurehPa, tsensor.Pressure)))
     logger.Info(fmt.Sprintf("    Humidity: %.1f%% (%s)", tsensor.Humidity, humidityDescription))
     logger.Info(strings.Repeat("-", 40))

     time.Sleep(2 * time.Second)
}

[soypat]

lots of good stuff and also some stuff to improve. hope this helps :)

[soypat]

maybe unexport

[gandarez]

This is specific to SPI but it defines the register address of SPI interface as well the other registers which are all exported. I don't think it's such a bit problem having them exported.

[soypat]

If the user already has access to the Read/Write layer, they don't really need them. They might need the registers but not this...

[soypat]

beware heap alloc here.

[gandarez]

how to avoid heap in this case?

[soypat]

Key is always pass in the spi's in-struct array to Tx. All you gotta do is fill it with the correct data.

s.bus.wbuf[0] = reg | SPI_RD_MSK
n := copy(s.bus.wbuf[:], data)
return s.bus.Tx(s.bus.wbuf[:n], s.bus.rbuf[:n])

[soypat]

Also, your driver is technically incorrect, you should always pass in equal length buffers to Tx, or one of them should be nil

[soypat]

heap

[gandarez]

how to avoid heap in this case?

[soypat]

Same rules as above. use in-struct arrays. please refer to https://deploy-preview-451--tinygo.netlify.app/docs/guides/driver-design/

If the path to avoiding heap allocations is not clear please leave a comment here with what is missing or could be improved: tinygo-org/tinygo-site#451