+ * See also: https://www.pololu.com/file/download/LPS25H.pdf?file_id=0J761
+ *Source code referenced: https://github.com/tkurbad/mipSIE/blob/master/python/AltIMU-10v5/i2c.py
+ */ +public class BaroTemp implements AutoCloseable { + private I2cDevice mDevice; + // Register addresses + private final int LPS_REF_P_XL = 0x08; // Reference pressure, lowest byte + private final int LPS_REF_P_L = 0x09; // Reference pressure, low byte + private final int LPS_REF_P_H = 0x0A; // Reference pressure, high byte + + private final int LPS_WHO_AM_I = 0x0F; // Returns 0xbd (read only) + + private final int LPS_RES_CONF = 0x10; // Set pressure and temperature resolution + + private final int LPS_CTRL_REG1 = 0x20; // Set device power mode / ODR / BDU + private final int LPS_CTRL_REG2 = 0x21; // FIFO / I2C configuration + private final int LPS_CTRL_REG3 = 0x22; // Interrupt configuration + private final int LPS_CTRL_REG4 = 0x23; // Interrupt configuration + + private final int LPS_INTERRUPT_CFG = 0x24;// Interrupt configuration + private final int LPS_INT_SOURCE = 0x25; // Interrupt source configuration + + private final int LPS_STATUS_REG = 0x27; // Status (new pressure/temperature data available) + + private final int LPS_PRESS_OUT_XL = 0x28; // Pressure output, loweste byte + private final int LPS_PRESS_OUT_L = 0x29; // Pressure output, low byte + private final int LPS_PRESS_OUT_H = 0x2A; // Pressure output, high byte + + private final int LPS_TEMP_OUT_L = 0x2B; // Temperature output, low byte + private final int LPS_TEMP_OUT_H = 0x2C; // Temperature output, high byte + + private final int LPS_FIFO_CTRL = 0x2E; // FIFO control / mode selection + private final int LPS_FIFO_STATUS = 0x2F; // FIFO status + + private final int LPS_THS_P_L = 0x30; // Pressure interrupt threshold, low byte + private final int LPS_THS_P_H = 0x31; // Pressure interrupt threshold, high byte + + // The next two registers need special soldering + private final int LPS_RPDS_L = 0x39;// Pressure offset for differential pressure computing, low byte + private final int LPS_RPDS_H = 0x3A; // Differential offset, high byte + private int mMillibarAdjust = 0; + + /** + * Create a new barometric pressure and temperature sensor driver connected on the given I2C bus. + * + * @param bus I2C bus the sensor is connected to. + * @throws IOException when a lower level does + */ + public BaroTemp(String bus) throws IOException { + PeripheralManager pioService = PeripheralManager.getInstance(); + mDevice = pioService.openI2cDevice(bus, SenseHat.I2C_LPS25H_ADDRESS); + // power down first + mDevice.writeRegByte(LPS_CTRL_REG1, (byte) 0); + // power up, data rate 12.5Hz (10110000) + mDevice.writeRegByte(LPS_CTRL_REG1, (byte) 0xb0); + if (0xBD != (mDevice.readRegByte(LPS_WHO_AM_I) & 0xFF)) { + throw new IOException("This does not seem to be a LPS25H"); + } + } + + @Override + public void close() throws IOException { + if (mDevice != null) { + try { + // power down device + mDevice.writeRegByte(LPS_CTRL_REG1, (byte) 0); + } catch (Exception any) { + // we tried + } + try { + mDevice.close(); + } finally { + mDevice = null; + } + } + } + + private int readSigned24(int a0, int a1, int a2) throws IOException { + int ret = (mDevice.readRegByte(a0) & 0xFF); + ret += ((int) mDevice.readRegByte(a1) & 0xFF) << 8; + ret += ((int) mDevice.readRegByte(a2) & 0xFF) << 16; + if (ret < 8388608) return ret; + else return ret - 16777216; + } + + private int readSigned16(int a0, int a1) throws IOException { + int ret = (mDevice.readRegByte(a0) & 0xFF); + ret += (mDevice.readRegByte(a1) & 0xFF) << 8; + if (ret < 32768) return ret; + else return ret - 65536; + } + + /** + * The sensor seems to have an offset to the actual pressure. You can find your local "real" + * pressure quite easily on the web. Get the measured value from the sensor and compute the + * difference. The value obtained can be passed to this method to "calibrate" your board's + * sensor. In the author's case the difference was 6.2 hPa which is quite significant. This + * error was confirmed with another (unrelated) sensor. + * + * @param hPa difference to actual air pressure in hectoPascal (hPa) or millibar. + * @throws IOException from I2cDevice + */ + public void setBarometerOffset(double hPa) throws IOException { + this.mMillibarAdjust = (int) Math.round(hPa * 4096); + } + + /** + * Fetch raw value, see the data sheet.Note that this call waits for data to be available. + * From the data sheet the (selected) refresh rate is 12.5 Hz so the max wait could be + * 1000/12.5 = 80 milliseconds with an average of 40 milliseconds. Call from asynchronous code + * if this is an issue. If your code calls this method less frequently then 12.5 times per + * second there will be no wait.
+ * + * @return The raw sensor value, adjusted by the given offset (if any). + * @throws IOException from I2cDevice + */ + public int getBarometerRaw() throws IOException { + // wait for data available + while (0 == (mDevice.readRegByte(LPS_STATUS_REG) & 2)) { + try { + Thread.sleep(1); + } catch (InterruptedException e) { + throw new IOException(e); + } + } + return readSigned24(LPS_PRESS_OUT_XL, LPS_PRESS_OUT_L, LPS_PRESS_OUT_H) + mMillibarAdjust; + } + + /** + * Fetch raw value, see the data sheet.Note that this call waits for data to be available. + * From the data sheet the (selected) refresh rate is 12.5 Hz so the max wait could be + * 1000/12.5 = 80 milliseconds with an average of 40 milliseconds. Call from asynchronous code + * if this is an issue. If your code calls this method less frequently then 12.5 times per + * second there will be no wait.
+ * + * @return The raw sensor value. + * @throws IOException from I2cDevice + */ + public int getTemperatureRaw() throws IOException { + // wait for data available + while (0 == (mDevice.readRegByte(LPS_STATUS_REG) & 1)) { + try { + Thread.sleep(1); + } catch (InterruptedException e) { + throw new IOException(e); + } + } + return readSigned16(LPS_TEMP_OUT_L, LPS_TEMP_OUT_H); + } + + /** + * Fetch air pressure in hPa (millibar).Note that this call waits for data to be available. + * From the data sheet the (selected) refresh rate is 12.5 Hz so the max wait could be + * 1000/12.5 = 80 milliseconds with an average of 40 milliseconds. Call from asynchronous code + * if this is an issue. If your code calls this method less frequently then 12.5 times per + * second there will be no wait.
+ * + * @return The current air pressure in hPa(millibar), adjusted by the given offset (if any). + * @throws IOException from I2cDevice + */ + public double getBarometer() throws IOException { + return getBarometerRaw() / 4096.0; + } + + /** + * Fetch the temperature in degrees Celcius. Note that the design of the SenseHat makes this + * more the temperature of the board then the actual (room) temperature! + *Also note that this call waits for data to be available. + * From the data sheet the (selected) refresh rate is 12.5 Hz so the max wait could be + * 1000/12.5 = 80 milliseconds with an average of 40 milliseconds. Call from asynchronous code + * if this is an issue. If your code calls this method less frequently then 12.5 times per + * second there will be no wait.
+ * + * @return The temperature as reported by the sensor in degrees Celcius. + * @throws IOException from I2cDevice + */ + public double getTemperature() throws IOException { + return 42.5 + getTemperatureRaw() / 480.0; + } +} diff --git a/sensehat/src/main/java/com/google/android/things/contrib/driver/sensehat/LedMatrix.java b/sensehat/src/main/java/com/google/android/things/contrib/driver/sensehat/LedMatrix.java index 9156138..18a4bfb 100644 --- a/sensehat/src/main/java/com/google/android/things/contrib/driver/sensehat/LedMatrix.java +++ b/sensehat/src/main/java/com/google/android/things/contrib/driver/sensehat/LedMatrix.java @@ -44,7 +44,7 @@ public class LedMatrix implements AutoCloseable { */ public LedMatrix(String bus) throws IOException { PeripheralManager pioService = PeripheralManager.getInstance(); - mDevice = pioService.openI2cDevice(bus, SenseHat.I2C_ADDRESS); + mDevice = pioService.openI2cDevice(bus, SenseHat.I2C_DISPLAY_ADDRESS); } /* package */ LedMatrix(I2cDevice device) { diff --git a/sensehat/src/main/java/com/google/android/things/contrib/driver/sensehat/SenseHat.java b/sensehat/src/main/java/com/google/android/things/contrib/driver/sensehat/SenseHat.java index c3bed66..b92a963 100644 --- a/sensehat/src/main/java/com/google/android/things/contrib/driver/sensehat/SenseHat.java +++ b/sensehat/src/main/java/com/google/android/things/contrib/driver/sensehat/SenseHat.java @@ -23,12 +23,47 @@ */ @SuppressWarnings({"unused", "WeakerAccess"}) public class SenseHat { - public static final int I2C_ADDRESS = 0x46; - public static final String BUS_DISPLAY = "I2C1"; + public static final int I2C_DISPLAY_ADDRESS = 0x46; + public static final int I2C_LPS25H_ADDRESS = 0x5C; + public static final String BUS_NAME = "I2C1"; public static final int DISPLAY_WIDTH = LedMatrix.WIDTH; public static final int DISPLAY_HEIGHT = LedMatrix.HEIGHT; + /** + * Connect to the LedMatrix of the SenseHat on a Raspberry Pi 3. + * @return The autoclosing LedMatrix object. + * @throws IOException If caused by the hardware. + */ public static LedMatrix openDisplay() throws IOException { - return new LedMatrix(BUS_DISPLAY); + return new LedMatrix(BUS_NAME); + } + + /** + * Connect to the LPS25H barometer/temperature of the SenseHat sensor on a Raspberry Pi 3. + * @return The autoclosing BaroTemp object. + * @throws IOException If caused by the hardware. + */ + public static BaroTemp openBaroTemp() throws IOException { + return new BaroTemp(BUS_NAME); + } + + /** + * Connect to the LedMatrix of the SenseHat. + * @param busName The name of the I2C bus device on a non-raspi3 board. + * @return The autoclosing LedMatrix object. + * @throws IOException If caused by the hardware. + */ + public static LedMatrix openDisplay(final String busName) throws IOException { + return new LedMatrix(busName); + } + + /** + * Connect to the LPS25H barometer/temperature of the SenseHat sensor. + * @param busName The name of the I2C bus device on a non-raspi3 board. + * @return The autoclosing BaroTemp object. + * @throws IOException If caused by the hardware. + */ + public static BaroTemp openBaroTemp(final String busName) throws IOException { + return new BaroTemp(busName); } }