DPS422XTSA1

DPS422 Digital barometric pressure & temp sensor for portable and IOT devices V1.3 Description The DPS422 is a miniaturized digital barometric air pressure sensor with high accuracy and low current consumption, capable of measuring both pressure and temperature. Pressure sensing is carried out using a capacitive sensor element, guaranteeing high accuracy over temperature. The small 2.0 x 2.5 x 0.73 mm package makes the DPS422 ideal for mobile applications and wearable devices. The pressure and temperature sensor elements are measured by a 24-bit ΣΔ ADC. Measurement results can be accessed over I2C or SPI, with an optional configurable interrupt and a result FIFO capable of holding 32 pressure and/or temperature measurements. Individual calibration coefficients are generated for each unit during testing, and stored in the fuse registers. These coefficients are used in the application to convert the measurement results to high accuracy pressure and temperature values. Features • • • • • • • • • • • • • • • Operation range: Pressure: 300 –1200 hPa. Temperature: -40°C – +85 °C. Pressure sensor precision: ± 0.005 hPa (or ±5 cm) (high precision mode). Relative accuracy: ± 0.06 hPa (or ±50 cm) Absolute accuracy: ± 1 hPa (or ±8 m) Temperature accuracy: ± 0.4°C. Pressure temperature sensitivity: < 0.5Pa/K Measurement time: Typical: 27.6 ms for standard mode (16x). Minimum: 3.6 ms for low precision mode. Average current consumption: 1.7 µA for pressure measurement, 2µA for temperature measurement @1Hz sampling rate, Standby: 1.2V & VDDIO > 0.6V or full soft reset. I2C Clock. fI2C 3.4 MHz SPI Clock fSPI 10 MHz Datasheet 9 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Functional description 4 Functional description The DPS422 is a versatile sensor, capable of providing fast, accurate pressure and temperature measurements at low current. In order to best support a wide range of applications there are a small number of configurable features which can be easily and quickly set on device start up. The DPS422 configurable features are: • Operating mode: - Command Mode (single-shot) - Background Mode (periodic) - Standby Mode • Pressure measurement precision and rate • Temperature measurement precision and rate • FIFO settings: - FIFO on/off - FIFO behaviour: stop-on-full/ streaming - FIFO depth - FIFO watermark level • Interrupt behaviour: - New measurement result available - FIFO full to watermark level - FIFO full - No interrupt The precision and measurement rate of the pressure and temperature measurements can be set independently by writing to the PSR_CFG and TEMP_CFG registers. The precision and measurement rates used are dictated by the requirements of the application, and a balance must be found between high precision and low power consumption. 4.1 Operating modes The DPS422 supports 3 different modes of operation: • Standby Mode: - Default mode after power on or reset. No measurements are performed. - All registers and compensation coefficients are accessible. • Command Mode: - One pressure and/or temperature measurement is performed according to the selected precision. - The sensor will return to Standby Mode when the measurement is finished, and the measurement result will be available in the dedicated result registers or FIFO output registers. - The FIFO can be used when the DPS422 is in Command mode. Several measurements can be requested before reading data back from the FIFO. • Background Mode: - Pressure and/or temperature measurements are performed continuously according to the selected measurement precision and rate. If enabled, the temperature measurement is performed immediately after the pressure measurement. - After each measurement is completed, the result will be available in the dedicated result registers if the FIFO is disabled. If the FIFO is enabled it will be added to the FIFO. - The FIFO can be used to store up to 32 measurement results and minimize the number of times the sensor must be accessed to read out the results. Using background mode and FIFO streaming mode, the DPS422 measures continuously and the most recent 32 measurements can be read at any time. Datasheet 10 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Functional description - The FIFO behaviour can be configured to either stop-on-full mode, which stops recording data once the FIFO is full, or to streaming mode, which will continue recording data once the FIFO is full, deleting the oldest data each time a new measurement is recorded. Attention: Switching power mode from Background Mode to Standby Mode is initiated by setting the measurement control bits [2:0] in MEAS_CFG to 0. If a measurement is taking place when these bits are set, the DPS422 will complete the measurement before switching power modes. The value of the Continuous Mode Flag, bit [6] in MEAS_CFG, will update to 0 once this measurement has been completed and the DPS422 has returned to Standby Mode. This bit can be monitored after initiating a power mode change if confirmation of the mode change is required. 4.2 Mode transition diagram The mode transition diagram is shown below. POR/Soft Reset Standby Mode: No measurements Lowest power setting Measurement Control [2:0]: 0b101 0b110 0b111 Background Mode: Periodic measurements according to rate and accuracy configuration Figure 3 Datasheet Measurement Control [2:0]: 0b000 0b100 Measurement Control Command: · Read coefficients & result · Configure Automatic return to Standby. Measurement Control [2:0] retains previous value. Measurement Control Command: · Read result Measurement Control [2:0]: 0b001 0b010 0b011 Manual Mode: Single measurements triggered by I2C/SPI, according to accuracy configuration. DPS422 mode transition diagram. 11 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Functional description 4.3 Measurement precision and rate When the DPS422 is in Background mode, the measurement precision and rate can be configured to match the requirements of the application. This reduces current consumption of the sensor and the system. In order to achieve a higher precision, the DPS422 will read the sensor multiple times ( oversampling ), and combine the readings into one result. This increases the current consumption and also the measurement time, reducing the maximum possible measurement rate. It is necessary to balance the accuracy and data rate required for each application with the allowable current consumption. The measurement precision, rate and time are set in the PSR_CFG and TEMP_CFG. The register descriptions contain information about the current consumption and the possible combinations of measurement precision, time, and rate. Temperature measurements must be enabled for the DPS422 to compensate for temperature drift in the pressure measurement. The rates of these measurements can be set independently, but temperature compensation is more accurate when temperature and pressure measurements are taken together. This reduces the maximum pressure measurement rate: Ratetemperature*Timetemperature + Ratepressure*Timepressure< 1 second. Measurement settings and use case examples contains a table with examples of combinations of pressure and temperature precision and rates for different use cases. The figure below show the temperature and pressure measurement sequence in Background mode. Figure 4 4.3.1 Background mode temperature and pressure measurements sequence Oversampling rate: kP Increasing the pressure or temperature oversampling rate increases the number of times the ΣΔ ADC will sample and average the input before generating an output value. Increasing the oversampling rate improves the measurement accuracy by reducing noise, but it also extends the length of time required to carry out a measurement. Increasing the measurement time increases average current consumption, as the DPS422 will spend longer in full power mode, and less time in standby mode. A balance must be found between current consumption and measurement accuracy, depending on the application requirements. Increasing the OSR is a good way to remove high frequency noise, but if the measurement time is too long, there will also be a filtering effect on transient pressure events such as spikes caused by doors or windows opening. If the application requires the DPS422 to detect these events, the oversampling rate should not be set too long. The oversampling rate will also have no effect on low frequency fluctuations caused by unstable ambient pressure. When calculating the pressure measurement from the output register value, it is necessary to include a calculation factor called kP. The value of kP changes depending on the oversampling rate selected for the measurement. The table below lists the oversampling rates and the respective kP values. Datasheet 12 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Functional description Table 9 kP values associated with each oversampling rate Bit Field Value No. Samples kP 000 256 524288 001 512 1572864 010 1024 3670016 011 2048 7864320 100 4096 253952 101 8192 516096 110 16384 1040384 111 32768 2088960 The kP values are used in the pressure calculation in the sections: • Calibration coefficients 4.4 FIFO operation The DPS422 FIFO can store up to the last 32 measurements of pressure and/or temperature. This reduces the overall system power consumption as the host processor does not need to continuously poll data from the sensor but can go into standby mode for longer periods of time. The FIFO can store any combination of pressure and temperature results, according to the background mode measurement rate settings. The least significant bit of the FIFO measurement result register PSR_B0 is used to indicate whether the measurement is a pressure or temperature result. The least significant bit is set to: • '1' if the result is a pressure measurement. • '0' if it is a temperature measurement. Note: The sensor uses 24 bits to store the measurement result, which is more than is necessary to cover the full dynamic range of the pressure sensor. Using the least significant bit to label the measurement type does not affect the precision of the result. The FIFO can be enabled in the CFG_REG. The data from the FIFO is read out from PSR_B2, PSR_B1 and PSR_B0 regardless of whether the result in the FIFO is a temperature or a pressure measurement. When a measurement has been read, the FIFO will automatically increment and place the next result in the data register. The FIFO empty bit is set in FIFO_STS when the FIFO is empty, in this case all FIFO reads return 0x800000. If the FIFO is full, the FIFO interrupt Full/WM bit in the FIFO_STS register is set. If the Interrupt select [3:0] bits in the CFG_REG register are set to 0x08, an interrupt will also be generated when the FIFO is full. If the FIFO watermark interrupt is configured by setting the Interrupt select [3:0] bits in the CFG_REG register to 0x04, the FIFO will generate an interrupt when the number of pressure and temperature results stored in the FIFO equals the configured watermark level. The FIFO can be configured to one of two behaviours when full: • FIFO stops recording new measurement results when full. • FIFO continues recording new measurement results when full, overwriting the oldest measurement. This behaviour can be configured by setting the FIFO Stop on full bit in the CFG_REG register. Setting this bit to 0 will enable streaming mode, setting to 1 will enable stop-on-full mode. Datasheet 13 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Functional description Attention: It is recommended not to poll the FIFO full flag bit in register INT STS faster once every 375 µs, as it is not updated immediately. Similarly the FIFO full status bit in register FIFO_STS should only be polled once every 250 µs. 4.5 Interrupt The DPS422 has a user configurable interrupt, which is generated on the SDO output. The DPS422 can be configured to generate an interrupt on the following events: • New measurement result available • FIFO full to configured watermark level • FIFO full The sensor uses the SDO output for the interrupt signal. The interrupt is not supported if the interface is 4-wire SPI. The interrupt is enabled and configured in the CFG_REG register. In I2C mode SDO serves as both interrupt and as the least significant bit in the device address. SDO has an internal pull up resistor, which defaults the address selection functionality to 0x77. The SDO output has a push-pull output stage so there is no need to use an external pull down resistor if the default I2C address is suitable for the application. Active high or active low interrupt operation can be selected using the Interrupt polarity bit, bit [3] in the CFG_REG register. Note: An external pull up resistor is never required on SDO and should not be used. The interrupt status can be read from the INT STS register. 4.6 Start-up sequence The DPS422 start-up sequence is shown below. This diagram shows when the registers are accessible for read/ write operations and also when the pressure/temperature measurements can start. Init. complete bit POR VDDIO VDD 8ms Startup Phase Figure 5 4.7 Measurements Possible DPS422 start-up sequence. Sensor interface The DPS422 can be accessed as a slave device through mode '11' SPI 3-wire, SPI 4-wire, or I2C serial interface. • I2C interface - The sensor's default interface. - The sensor's address is 0x77 (default) or 0x76 (if the SDO pin is pulled-down to GND). • SPI interface Datasheet 14 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Functional description - The sensor will switch to SPI configuration if it detects an active low on the CSB pin. SPI 4-wire is the default SPI interface. - To enable SPI 3-wire configuration, a bit must be set in the CFG_REG register after start up. More details about digital interfaces are available in the Digital interfaces section. Datasheet 15 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Pressure measurement 5 Pressure measurement The DPS422 is a single die MEMS pressure sensor which makes use of a capacitive measurement principle. The DPS422 sensor element consists of a number of sealed vacuum cells. Each cell consists of a hollow, evacuated cavity with a flexible membrane sealing the top. The top membrane and the bottom of the cell are electrodes, which form a capacitor. Due to the pressure difference between the interior of the cell and the ambient environment, the top membrane is deflected towards the bottom of the cell. The vacuum cells are combined in a parallel measurement configuration, to increase the sensitivity and noise performance of the DPS422. Increasing ambient pressure causes greater deflection towards the bottom of the cell and hence and increase in the capacitance between the membrane and the bottom of the cell. Decreasing ambient pressure reduces the deflection of the membrane and reduces the capacitance between the membrane and the bottom of the cell. Pressure measurement is carried out by measuring the capacitance between the top and bottom of the cells and applying a calculation to the capacitance result to determine the pressure in Pa. It is also required to include a temperature correction in this calculation to eliminate temperature drift from the output. 5.1 Pressure measurement results After starting the measurements, the latest pressure and temperature raw data will be available as 24-bit 2's complement numbers in their respective result registers if the FIFO is disabled: PSR_B2 to PSR_B0, and TMP_B2 to TMP_B0. If the FIFO is enabled, all measurement results will be stored in registers PSR_B2 to PSR_B0. In this case, the register value will update to the next result stored in the FIFO after each read. The least significant bit of PSR_B0 will read "1" if the measurement is a pressure reading, or "0" if the measurement is a temperature reading. When all of the FIFO values have been read, the result register will be set to 0x800000. When the FIFO is disabled, reading the result register will not affect the register value, it will only be updated when a new measurement is completed. All measurement data can be read in a single command using auto-increment read. 5.1.1 Calculating pressure reading To calculate the DPS422 pressure reading, it is necessary to first read and parse the calibration coefficient registers from addresses 0x26 to 0x39. These values only need to be read and parsed once for each device, they are fused in memory and will not change during operation. The method to generate the Calibration Coefficient values is described in the Calibration coefficients section of this document. The pressure values stored in the result registers must be scaled according to the oversampling rate. The numbers in the registers must be divided by kP before they are used in the pressure reading calculation formula. The kP values for each oversampling option can be found in Oversampling rate: kP. PresSCALED = PresRAW / kP TempX = TempRAW / 1048576 TempSCALED = (8.5 x TempX) / (1 + 8.8 x TempX) Where: • PresRAW is the 24 bit, 2's complement number read from the pressure output registers or FIFO • TempRAW is the 24 bit, 2's complement number read from the pressure output registers or FIFO Equation 1 Datasheet Deriving the scaled pressure and temperature values 16 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Pressure measurement Once the calibration coefficients have been read, and pressure and temperature register values have been read and scaled, the pressure reading can be calculated using the following formula: PresCALIBRATED= C00 + [C10 x PresSCALED] + [C01 x TempSCALED] + [C20 x PresSCALED2] + [C02 x TempSCALED2] + [C30 x PresSCALED3] + [C11 x PresSCALED x TempSCALED] + [C12 x PresSCALED x TempSCALED2] + [C21 x PresSCALED2 x TempSCALED] Where: • C00, C10, C01, C20, C02, C30, C11, C12 and C21 are the calibration coefficients read from registers 0x26 to 0x39. Equation 2 Datasheet DPS422 pressure output calculation 17 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Temperature measurement 6 Temperature measurement The DPS422 temperature measurement uses a silicon bandgap temperature sensor, measuring the base-emitter voltage (Vbe) of two BJT transistors, biased at different currents (IC1 and IC2). This measurement is used at a system level in the pressure output calculation to correct any temperature related measurement drift. The temperature of the transistors can be accurately determined by measuring the difference in voltage between both and applying the formula: ΔVBE = ((K*T)/ q) * (ln(IC1 / IC2) Where T is the temperature in Kelvin, K is Boltzmann's constant and q is the charge of a single electron. The measurement rate and precision (oversampling) can be modified by writing to the TEMP_CFG register, as described in the Measurement precision and rate section. Note: 6.1 For ambient temperature sensing, full system modeling should be carried out across temperature. This will account for internal heating effects of the system when calculating the ambient temperature value. One time calculation of A' and B' coefficients In order to calculate temperature output values in °C, it is first necessary to calculate two coefficients, A' and B'. These coefficients are calculated from values stored in the DPS422 calibration coefficients registers, and do not change. These two coefficients can be calculated once on device start up and then stored in memory to be used in all future high accuracy temperature measurements. The steps required to calculate A' and B' are below, calculation constants can be found in Table 10. 1. Read T_Vbe, T_dVbe and T_gain: These parameters are read directly from the calibration coefficient registers 0x20 to 0x22. These three values are in 2's complement. 2. Calculate VBE, ΔVBE and AADC: These values are calculated directly from the calibration coefficient values: • VBE = T_Vbe × 1.05031E-4 + 0.463232422 • ΔVBE = T_dVbe × 1.25885E-5 + 0.04027621 • AADC = T_gain × 8.4375E-5 + 0.675 3. Calculate VBE_CAL and ΔVBE_CAL: • VBE_CAL = VBE / AADC • ΔVBE_CAL= ΔVBE / AADC 4. Calculate calibration Temperature TCALIB: • TCALIB = A0 × ΔVBE_CAL - 273.15 5. Calculate VBE_CAL(TREF), the VBE value at reference temperature TREF: • VBE_CAL(TREF) = VBE_CAL- (TCALIB - TREF) × (TC_VBE) 6. Calculate PTAT correction coefficient: • kPTAT = [VBE_TARGET(TREF) - VBE_CAL(TREF) ] × kPTAT_CORNER + kPTAT_CURVATURE 7. Calculate A' and B' coefficients: • A' = A0 × (VBE_CAL + α × ΔVBE_CAL) × (1 +kPTAT) • B' = -273.15 × (1 + kPTAT) - kPTAT × TCALIB Datasheet 18 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Temperature measurement 6.2 Calculating temperature output using A' and B' Once the A' and B' coefficients have been calculated once, they can be stored in the host system and used for all future high accuracy temperature calculations for that DPS422 unit. The calculation of high accuracy temperature readings using A' and B' is a four step process, shown below. 1. Read out temperature result TRAW from registers TMP_B2 to TMP_B0 or FIFO, if enabled. 2. Scale the temperature measurement: • TCAL = TRAW / 1048576 3. Calculate µ coefficient: • μ = TCAL / (1 + α × TCAL) 4. Calculate TOUT: • TOUT =( A' × μ) + B' 6.3 A' and B' calculation constants The following table lists all of the coefficients required to calculate the A' and B' coefficients, as described in the One time calculation of A' and B' coefficients section. Table 10 A' and B' calculation constants Name Unit Value TREF °C 27 VBE_TARGET(TREF) V 0.687027 α - 9.45 TC_VBE V -1.735E-3 kPTAT_CORNER - -0.8 kPTAT_CURVATURE - 0.039 A0 K 5030 Datasheet 19 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Applications 7 Applications 7.1 Measurement settings and use case examples The DPS422 provides versatile pressure measurements for a wide range of applications. The requirements of these applications can be very different, and so the DPS422 can be quickly configured with a couple of register writes to ensure the speed, accuracy and current consumption are in line with the application priorities. Table 11 Measurement settings and use case examples Use Case Performance Pressure Register Configuration Address: 0x06 Temperature Register Configuration Address: 0x07 FIFO Enabled? Address: 0x09 Other Weather Station (Low power) 5 Pa precision. 1 pr sec. 3 µA FIFO disabled 0x01 0x00 Bit 1 = 0 Start background measurements (addr 0x08) Indoor navigation (Standard precision, background mode) 10 cm precision. 0x14 2 pr sec. 35 µA FIFO enabled 0x93 Bit 1 = 1 Start background measurements (addr 0x08) Sports (High precision, high rate, background mode) 5 cm precision 4 pr sec. 175 µA FIFO enabled 0xA3 Bit 1 = 1 Start background measurements (addr 0x08) 7.2 0x26 Application circuit examples The example application circuits below demonstrate the connection of the I2C and SPI serial interfaces. • In I2C mode, the SDO pin can be used for interrupt output and/or to set the least significant bit of the device address. • In 3-wire SPI mode, the SDO pin can be used for interrupt output. • In 4-wire SPI mode, the SDO pin can only be used as the serial data output. The DPS422 analog core supply voltage is internally regulated, guaranteeing robustness to external VDD supply variations within the specified range. The simplest voltage supply solution is to connect VDD and VDDIO to 1.8V supply and add a suitable decoupling capacitor to reduce VDD ripple below 50mVpp. Datasheet 20 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Applications Processor I2C Serial Interface DPS422 VDDIO SDA SCL INT R1 SDI VDDIO R2 1.2V to 3.6V VDD 1.7V to 3.6V C1 SCK VDDIO Interrupt (optional) C2 SDO R3 (I²C Addr. LSB only) N.C. Figure 6 CSB GND Application circuit example using the I2C serial interface. Processor SPI Serial Interface DPS422 MISO SDO MOSI SDI SCL SCK SS CSB 1.2V to 3.6V VDD C1 VDDIO Figure 7 SPI Serial Interface GND DPS422 IO SDI SCL SCK 1.2V to 3.6V VDD VDDIO SS INT Datasheet C2 Application circuit example using the SPI 4-wires serial interface Processor Figure 8 1.7V to 3.6V CSB Interrupt (optional) SDO 1.7V to 3.6V C1 C2 GND Application circuit example using the SPI 3-wire serial interface 21 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Applications Table 12 Component values Component Symbol Values Unit Min. Pull-up/down Resistor Supply Blocking Capacitor Datasheet Typ. Note / Test Condition Max. R1, R2 10 kΩ R3 100 kΩ R3 is optional and will set the address to 0x76 instead of 0x77. nF The blocking capacitors should be placed as close to the package pins as possible. C1, C2 100 100 22 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Digital interfaces 8 Digital interfaces The DPS422 measurement data, calibration coefficients, Product ID and configuration registers can be accessed through both the I2C and SPI serial interfaces. The SPI interface can be configured to operate in 3-wire or 4-wire mode. In I2C and SPI 3-wire, an interrupt output can be implemented on the SDO pin. The SPI interface only supports mode '11' ( CPOL=CPHA='1' ) in 4-wire and 3-wire configuration. The following commands are supported by the I2C interface: • Single byte read • Single byte write • Multi-byte read, with automatic register increment • Multi-byte write, with automatic register increment The following commands are supported by the SPI interface: • Single byte read • Single byte write • Multi-byte read, with automatic register increment Note: Multi-byte write is not supported by the SPI interface. The communication interface is selected using the CSB pin: • If CSB is connected to VDDIO, the I2C interface is active. • If CSB is connected to ground, the SPI interface is active. Once CSB has been pulled down, the I2C interface is disabled until the next power-on-reset. If CSB is high, the I2C interface is selected by addressing the DPS422 over the I2C bus. After this, the I2C interface is locked, and pulling down CSB will not activate the SPI interface. The SPI interface can only be selected by pulling CSB low after the next power-on-reset, before the DPS422 is addressed over I2C . 8.1 I2C interface The I2C slave interface is compatible with Philips I2C Specification version 2.1. The I2C interface supports standard, fast and high speed mode. The sensor's address is 0x77 if the SDO pin is left floating or pulled-up to VDDIO, or 0x76 if the SDO pin is pulleddown to GND. The I2C interface uses the pins described in the Pin configuration section. The basic timing is shown in the diagram below: P SDA SCL S or Sr 1 2 START or repeated START condition Figure 9 Acknowledgement signal from receiver Acknowledgment signal from slave MSB 7 8 9 1 2 3 to 8 Byte complete, interrupt within slave 9 ACK ACK Clock line held LOW while interrupts are serviced Sr Sr or P STOP or repeated START condition I2C timing diagram In one access, without a stop command, incremental read (address is auto increment) and auto-incremental write are supported. The read and write access is shown below: Datasheet 23 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Digital interfaces I2C Write Command Srt Slave Addr. Wr Ack Register Addr. Ack Register Data Wr Ack Register Addr. Ack Register Data 0 Wr Ack Register Addr. Ack rSrt Master Slave Ack Stp I2C Multibyte Write Command Srt Slave Addr. Srt – Start Stp – Stop rSrt – Repeated Start Wr – Write Rd – Read Ack – Acknowledge Nack – Not Acknowledge Register Data n Ack Stp I2C Read Command Srt Slave Addr. Slave Addr. Rd Ack Register Data Nack Stp I2C Multibyte Read Command Srt Slave Addr. Wr Ack Register Addr. Ack rSrt Slave Addr. Rd Ack Register Data 0 Ack Figure 10 8.2 Register Data n Nack Stp I2C write and read commands SPI interface The SPI interface is compatible with SPI mode '11' ( CPOL = CPHA = '1'. The SPI interface has two modes: 4-wire and 3-wire. The protocol for 3-wire and 4-wire SPI is similar. The 3-wire SPI protocol uses a single shared data line, the 4wire SPI protocol uses separate Serial Data Out (SDO) and Serial Data In (SDI) data lines. The naming of these data lines refers to the direction of data respective to the slave device. 3-wire SPI mode is selected by setting bit[0] in the CFG_REG register to '1'. The SPI interface uses the pins described in the Pin configuration section. Refer to Application circuit examples for connection instructions. The SPI protocol is shown in the diagram below: Figure 11 SPI protocol, 4-wire without interrupt An SPI write is carried out by setting CSB low and sending a control byte followed by register data. The control byte consist of the SPI register address (full register address without bit 7) and the write command (bit 7 = RW = '0'). Setting CSB high ends the transaction. The SPI write24protocol is described in the diagram below. Datasheet 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Digital interfaces An SPI read is initiated by setting CSB low and sending a single control byte. The control byte consist of the SPI register address (full register address without bit 7) and the read command (bit 7 = RW = '1'). After writing the control byte, data is sent out of the SDO pin ( SDI in 3-wire mode); the register address is automatically incremented. Setting CSB high ends the SPI read transaction. The SPI read protocol is shown in the diagram below: 3 Wire SPI Read or Write Command CSB CSB Hi CSB Low CSB Hi SCL SCL Hi SCL SCL Hi SDI R/W Reg. Address 4 Wire SPI Read or Write Command CSB CSB Hi SCL Data in/out CSB Low CSB Hi SCL SCL Hi SCL Hi SDI R/W Reg. Address SDO Data in Data out 3 Wire SPI Multibyte Read Command CSB CSB Hi CSB Low CSB Hi SCL SCL Hi SCL SCL Hi SDI R/W Reg. Address Data out 0 Data out n 4 Wire SPI Multibyte Read Command CSB CSB Hi CSB Low CSB Hi SCL SCL Hi SCL SCL Hi SDI R/W Reg. Address SDO Figure 12 Data out 0 Data out n SPI write, read protocol diagrams 8.3 Interface parameter specification 8.3.1 General interface parameters The general interface parameters are given in the table below: Table 13 Interface parameters Parameter Symbol Values Min. Input voltage for low logic level at input pins Vlow_in Input voltage for high logic level at input pins Vhigh_in Datasheet Typ. 25 Note or Test Condition V VDDIO=1.2V to 3.6V V VDDIO=1.2V to 3.6V Max. 0.3 * VDDIO 0.7 * VDDIO Unit 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Digital interfaces Table 13 Interface parameters (continued) Parameter Symbol Values Min. Typ. Unit Note or Test Condition Max. Output - low level for I2C Vlow_SDI 0.1 * VDDIO V VDDIO=1.8V, iol=2mA Output voltage for low level at pin SDI for I2C Vlow_SDI_1.2 0.2* VDDIO V VDDIO=1.20V, iol=1.3mA Output voltage for high level at pins SDO, SDI Vhigh_out 0.8 * VDDIO V VDDIO=1.8V, iol=1mA (SDO, SDI) Output voltage for high level at pins SDO, SDI Vhigh_out_1.2 0.6 * VDDIO V VDDIO=1.2V, iol=1mA (SDO, SDI) Pull-up resistor Rpull 60 I2C bus load capacitor Cb Datasheet 26 120 180 kohm Internal pull-up resistance to VDDIO 400 pF On SDI and SCK 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Digital interfaces 8.3.2 I2C timing parameters The I2C timing is shown in the diagram below and corresponding values are given in the table below. The naming refers to I2C Specification version 2.1, the abbreviations used "S&F mode" = standard and fast mode, "HS mode" = high speed mode, Cb = bus capacitance on SDA line. P SDA SCL S or Sr Acknowledgement signal from receiver Acknowledgment signal from slave MSB 1 7 2 8 9 1 2 9 3 to 8 ACK START or repeated START condition ACK Byte complete, interrupt within slave Sr Clock line held LOW while interrupts are serviced Sr or P STOP or repeated START condition Data transfer on the I2C-bus Clock tHold SCL Duty Cycle SDA tSetup Figure 13 I2C timing diagram Table 14 I2C timings Parameter Symbol Values Unit Note or Test Condition 20 ns S&F mode 5 ns HS mode 0 ns S&F&HSmode, 70 % S&F mode, 55 % HS mode, Min. Data setup time on SDI pin tSetup Data hold time on SDI pin tHold Duty Cycle DC Datasheet 27 Typ. Max. 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Digital interfaces 8.3.3 SPI timing parameters The SPI timing diagram is shown in the figure below and the corresponding values are given in the table below. All timings apply both to 4-wire and 3-wire SPI. Figure 14 SPI timing diagram Table 15 SPI timings Parameter Symbol Values Unit Note or Test Condition 30 % VDDIO = 1.2V 20 % VDDIO = 1.8V/3.6V Min. Duty Cycle (Thigh%) SPI_DC Typ. Max. SDI setup time T_setup_sdi 2 ns SDI hold time T_hold_sdi 2 ns Clock SPI_CLK CSB setup time T_setup_csb 10 CSB hold time Datasheet 28 MHz 15 ns 15 ns 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register map 9 Register map The DPS422 user registers are listed and described below. The calibration coefficient registers can be found in the Calibration coefficients section. Table 16 DPS422 Register Map Register Name Addr. Bit 7 Bit 6 PSR_B2 0x00 Pressure measurement MSB 0x80 PSR_B1 0x01 Pressure measurement LSB 0x00 PSR_B0 0x02 Pressure measurement XLSB 0x00 TMP_B2 0x03 Temperature measurement MSB 0x80 TMP_B1 0x04 Temperature measurement LSB 0x00 TMP_B0 0x05 Temperature measurement XLSB 0x00 PSR_CFG 0x06 - Pressure measurement rate [2:0] - Pressure measurement resolution [3:0] 0x00 TEMP_CFG 0x07 Must be set to 1 Temperature measurement rate [2:0] - Temperature measurement resolution [3:0] 0x80 MEAS_CFG 0x08 Init. Cont. complete mode flag - Measurement control [2:0] 0x00 CFG_REG 0x09 Interrupt select [3:0] INT STS 0x0A - - - - WM_CFG 0x0B - - - Watermark level[4:0] FIFO_STS 0x0C FIFO fill level[5:0] RESET 0x0D FIFO flush PROD_ID 0x1D Revision ID[3:0] - Bit 5 Temp. data ready Bit 4 Press. data ready Bit 3 Bit 2 Interrupt FIFO polarity Stop on full - Bit 1 FIFO enable Bit 0 SPI mode - 0x00 FIFO Temp. Press. 0x00 interrupt interrupt interrupt Full / WM 0x1F FIFO FIFO Full / WM empty - Reset Value 0x00 Soft reset[3:0] 0x00 Product ID[3:0] 0x1A Attention: To ensure correct functionality, registers not listed in this register map must not be accessed. Datasheet 29 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions 10 Register descriptions 10.1 PSR_B2 Register containing most significant byte of the pressure measurement result. Address: 0x00 Reset Value: 0x80 Table 17 PSR_B2 register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 PSR23 PSR22 PSR21 PSR20 PSR19 PSR18 PSR17 PSR16 Table 18 PSR_B2 bit fields Bit Name Bits Pressure measurement MSB 10.2 Type Description R Pressure measurement result bits 23 to 16. PSR_B1 Register containing middle byte of the pressure measurement result. Address: 0x01 Reset Value: 0x00 Table 19 PSR_B1 register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 PSR15 PSR14 PSR13 PSR12 PSR11 PSR10 PSR9 PSR8 Table 20 PSR_B1 bit fields Bit Name Bits Pressure measurement LSB 10.3 Type Description R Pressure measurement result bits 15 to 8. PSR_B0 Register containing least significant byte of the pressure measurement result. Address: 0x02 Reset Value: 0x00 Table 21 PSR_B0 register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 PSR7 PSR6 PSR5 PSR4 PSR3 PSR2 PSR1 PSR0 Datasheet 30 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions Table 22 PSR_B0 bit fields Bit Name Bits Type Description Pressure measurement XLSB R Pressure measurement result bits 7 to 0. 10.4 TMP_B2 Register containing most significant byte of the temperature measurement result. Address: 0x03 Reset Value: 0x80 Table 23 TMP_B2 register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 TMP23 TMP22 TMP21 TMP20 TMP19 TMP18 TMP17 TMP16 Table 24 TMP_B2 bit fields Bit Name Bits Temperature measurement MSB 10.5 Type Description R Temperature measurement result bits 23 to 16. TMP_B1 Register containing middle byte of the temperature measurement result. Address: 0x04 Reset Value: 0x00 Table 25 TMP_B1 register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 TMP15 TMP14 TMP13 TMP12 TMP11 TMP10 TMP9 TMP8 Table 26 Bit Name TMP_B1 bit fields Bits Temperature measurement LSB 10.6 Type Description R Temperature measurement result bits 15 to 8. TMP_B0 Register containing least significant byte of the temperature measurement result. Address: 0x05 Reset Value: 0x00 Datasheet 31 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions Table 27 TMP_B0 register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 TMP7 TMP6 TMP5 TMP4 TMP3 TMP2 TMP1 TMP0 Table 28 TMP_B0 bit fields Bit Name Bits Type Description Temperature measurement XLSB R Temperature measurement result bits 7 to 0. Datasheet 32 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions 10.7 PSR_CFG Configuration register for pressure measurement. Pressure or stress measurements can be enabled. Pressure measurement rate and resolution can be modified. Address: 0x06 Reset Value: 0x00 Table 29 PSR_CFG register Bit 7 Bit 6 Bit 5 Bit 4 - Pressure measurement rate[2:0] Bit 3 Bit 2 Bit 1 - Pressure measurement resolution[2:0] Table 30 PSR_CFG bit fields Bit Name Bits Type Description Pressure measurement rate[2:0] RW Pressure measurement rate: • 000 - 1 sample/sec • 001 - 2 samples/sec • 010 - 4 samples/sec • 011 - 8 samples/sec • 100 - 16 samples/sec • 101 - 32 samples/sec • 110 - 64 samples/sec • 111 - 128 samples/sec Pressure measurement resolution[2:0] RW Pressure measurement resolution: • 000 - 256 samples - 1x decimation • 001 - 512 samples - 2x decimation • 010 - 1024 samples - 4x decimation • 011 - 2048 samples - 8x decimation • 100 - 4096 samples - 16x decimation • 101 - 8192 samples - 32x decimation • 110 - 16384 samples - 64x decimation • 111 - 32768 samples - 128x decimation Datasheet 33 Bit 0 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions Table 31 Precision (PaRMS) and pressure measurement time (ms) versus oversampling rate Oversampling (PSR_CFG[3:0]) 1x (0000) Measurement time 3.6 (ms) Precision (PaRMS) Table 32 2x (0001) 4x (0010) 8x (0011) 16x (0100) 32x (0101) 64x (0110) 128x (0111) 5.2 8.4 14.8 27.6 53.2 104.4 206.8 1.2 0.9 0.5 5 2.5 Estimated current consumption (µA) Oversampling (PSR_CFG[3:0]) 1x (0000) 2x (0001) 4x (0010) 8x (0011) 16x (0100) 32x (0101) 64x (0110) 128x (0111) 2.1 2.7 3.8 6.1 11 20 38 75 Measurements pr sec. (PM_RATE([2:0]) 1 (000) 2 (001) 4 (010) 8 (011) Note: The current consumption can be calculated as the Measurement Rate * Current Consumption of 1 measurement per. sec. 16 (100) n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. 32 (101) 64 (110) 128 (111) n.a. n.a. n.a. Note: The table shows the possible combinations of Pressure Measurement Rate and oversampling when no temperature measurements are performed. When temperature measurements are performed the possible combinations are limited to Ratetemperature x Measurement Timetemperature + Ratepressure x Measurement Timepressure < 1 second. Temperature measurement time versus temperature oversampling rate is similar to pressure measurement time versus pressure oversampling rate. Datasheet 34 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions 10.8 TEMP_CFG Configuration register for temperature measurements. Temperature measurement rate and resolution can be modified. Address: 0x07 Reset Value: 0x00 Table 33 TEMP_CFG register Bit 7 Bit 6 Bit 5 Bit 4 Must be set to 1 Temperature measurement rate [2:0] Table 34 TEMP_CFG bit fields Bit Name Bits Type Must be set to 1 RW Bit 3 Bit 2 Bit 1 - Temperature measurement resolution [2:0] Description Warning: This bit must be set to '1' to configur the temperature measurement correctly. If this bit is not set, the temperature and pressure measurements will not function correctly. Temperature measurement rate [2:0] RW Temperature measurement rate: • 000 - 1 sample/sec • 001 - 2 samples/sec • 010 - 4 samples/sec • 011 - 8 samples/sec • 100 - 16 samples/sec • 101 - 32 samples/sec • 110 - 64 samples/sec Temperature measurement resolution [2:0] RW Temperature measurement resolution: • 000 - 256 samples - 1x decimation • 001 - 512 samples - 2x decimation • 010 - 1024 samples - 4x decimation • 011 - 2048 samples - 8x decimation • 100 - 4096 samples - 16x decimation • 101 - 8192 samples - 32x decimation • 110 - 16384 samples - 64x decimation • 111 - 32768 samples - 128x decimation Table 35 Bit 0 Temperature measurement time (ms) versus oversampling rate Oversampling (TEMP_CFG[2:0]) Single (000) 2 times (001) 4 times (010) 8 times (011) 16 times (100) 32 times (101) 64 times (110) Measurement time (ms) 5.2 8.4 14.8 27.6 53.2 104.4 206.8 Datasheet 35 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions 10.9 MEAS_CFG Configuration register for general measurement settings. Address: 0x08 Reset Value: 0x00 Table 36 MEAS_CFG register Bit 7 Bit 6 Bit 5 Init. complete Cont. mode Temp. data flag ready Bit 4 Bit 3 Bit 2 Bit 1 Press. data ready - Measurement control [2:0] Bit 0 Table 37 MEAS_CFG bit fields Bit Name Bits Type Description Init. complete R Status bit set when initialisation procedure is complete. Cont. mode flag R Status bit set when DPS422 is in continuous measurement mode. Temp. data ready R Status bit set when new temperature measurement data is available. Cleared when register 0x05 is read. Press. data ready R Status bit set when new pressure measurement data is available. Cleared when register 0x02 is read. Measurement control [2:0] RW Configuration register controlling measurement mode: • 000 - Idle / Stop Background • 001 - Pressure Measurement • 010 - Temperature Measurement • 011 - Pressure and Temperature Measurement one shot • 100 - Idle / Stop Background • 101 - Continuous Pressure Measurement • 110 - Continuous Temperature Measurement • 111 - Continuous Pressure and Temperature Measurement Datasheet 36 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions 10.10 CFG_REG Interrupt, SPI mode and FIFO configuration register. Address: 0x09 Reset Value: 0x00 Table 38 Bit 7 CFG_REG register Bit 6 Bit 5 Bit 4 Interrupt select[3:0] Bit 3 Bit 2 Bit 1 Bit 0 Interrupt polarity FIFO Stop on full FIFO enable SPI mode Table 39 CFG_REG bit fields Bit Name Bits Type Description Interrupt select[3:0] RW Select interrupt source: • 0000 - no interrupt enabled • 0001 - Pressure Interrupt enabled • 0010 - Temperature Interrupt enabled • 0011 - Pressure & Temperature Interrupt enabled • 0100- FIFO Watermark Interrupt enabled • 1000- FIFO FULL Interrupt enabled All other settings are invalid. Interrupt pin(SDO pin) is cleared when the Interrupt Status Register (0x0A) is read. Interrupt polarity RW Interrupt active polarity: • 0 - Active low • 1 - Active high Note: Interrupt can only be output when the DPS422 is in I2C or 3-wire SPI modes. FIFO Stop on full RW Configures FIFO behaviour when full: • 0 - FIFO in streaming mode. When full, oldest data is overwritten as new data is available. • 1 - FIFO in stop on full mode. When full, old data is retained, new data is not stored. FIFO enable RW Enables pressure and temperature result FIFO: • 0 - FIFO is disabled. Old results are not stored. Pressure and temperature results stored in respective results registers. • 1 - FIFO is enabled. Results are read from result registers 0x00 - 0x02. Up to 32 results can be stored. SPI mode RW Configures the SPI protocol used: • 0 - 4-wire SPI interface. • 1 - 3-wire SPI interface Datasheet 37 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions 10.11 INT STS Register reflecting the current status of the DPS422 interrupt sources. All bits are clear on read. Address: 0x0A Reset Value: 0x00 Table 40 INT STS register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 - - - - - FIFO interrupt Full / WM Temp. interrupt Press. interrupt Note: The interrupt pin, and this register itself are cleared when this register is read. Table 41 INT STS bit fields Bit Name Bits Type Description FIFO interrupt Full / WM R This bit is set when FIFO is full or when FIFO reaches watermark level. Source depends on setting inCFG_REG register. Note: This bit should not be polled faster than once per 375 µs. Temp. interrupt R This bit is set when new temperature data is available. Press. interrupt R This bit is set when new pressure data is available. Datasheet 38 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions 10.12 WM_CFG FIFO watermark level configuration register. Address: 0x0B Reset Value: 0x1F Table 42 WM_CFG register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 - - - Watermark level[4:0] Bit 2 Bit 1 Bit 0 Table 43 WM_CFG bit fields Bit Name Bits Type Description Watermark level[4:0] RW Configures number of measurement results which must be in the FIFO to trigger the FIFO watermark interrupt. • 0x00 - Interrupt generated when FIFO contains 1 unread measurement result. • 0x1F - Interrupt generated when FIFO contains 32 unread measurement results. Datasheet 39 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions 10.13 FIFO_STS FIFO status register, reflecting FIFO fill and watermark status. Address: 0x0C Reset Value: 0x00 Table 44 FIFO_STS register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 FIFO fill level[5:0] Bit 2 Bit 1 Bit 0 FIFO Full / WM FIFO empty Table 45 FIFO_STS bit fields Bit Name Bits Type Description FIFO fill level[5:0] R This bit field contains the number of pressure and/or temperature measurements currently stored in the measurement results FIFO. FIFO Full / WM R This bit is set when FIFO is full or when FIFO reaches watermark level. Source depends on setting in WM_CFG register. Note: FIFO empty R This bit is updated every 250 µs This bit is set when the FIFO is empty. • 0 - FIFO currently contains data • 1 - FIFO does not currently contain data Note: Datasheet This bit is updated every 250 µs 40 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Register descriptions 10.14 RESET Reset register allows soft reset of the DPS422, and flushing of the measurement results FIFO. Address: 0x0D Reset Value: 0x00 Table 46 RESET register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 FIFO flush - - - Soft reset[3:0] Table 47 Bit 2 Bit 1 Bit 0 RESET bit fields Bit Name Bits Type Description FIFO flush W Setting this bit to 1 clears all data in the measurement results FIFO. Soft reset[3:0] W Two soft reset options are available, depending on the value sent to this bit field. • 0b1000: Reset configuration registers without eFuse refresh. Duration ~0.7ms. • 0b1001: Full reset. Similar to power-on-reset, all registers are reset and eFuses refresh is carried out. Duration ~3ms. Note: 10.15 Only the listed values should be written to the soft reset bit field. Writing incorrect values may result in unexpected behaviour. PROD_ID Product ID register storing product and revision information. Address: 0x1D Reset Value: 0x1A Table 48 Bit 7 PROD_ID register Bit 6 Bit 5 Bit 4 Revision ID[3:0] Bit 3 Bit 2 Bit 1 Bit 0 Product ID[3:0] Table 49 PROD_ID bit fields Bit Name Bits Type Description Revision ID[3:0] R DPS422 revision number, incremented on metal and silicon revisions. Product ID[3:0] R DPS422 product ID number. Always set to 0xA. Datasheet 41 2018-08-02 DPS422 Digital barometric pressure & temp sensor for portable and IOT devices Calibration coefficients 11 Calibration coefficients The DPS422 register map contains a number of fused coefficients which are used in the calculation of pressure and temperature measurements. The three temperature measurement coefficients are stored across three registers at addresses 0x20 to 0x22. These coefficients are individually calculated and fused in each DPS422, they must be used to accurately convert the temperature measurement value stored in the results registers TMP_B0 to TMP_B2 into a temperature value in °C. Pressure calibration coefficients are stored in register addresses 0x26 to 0x39. These coefficients are also individually measured and fused for each DPS422 unit and must be used in the calculation of pressure measurement results to eliminate any measurement non-linearities caused by temperature shift. The following tables shows the register layout of the calibration coefficients. It is recommended to block read these coefficient registers and then parse according to the bit labellings in the table. Table 50 DPS422 Temperature Calculation Coefficients Register Name Addr. Bit 7 T_GAIN_COEFF 0x20 T_gain T_dVBE_COEFF 0x21 T_dVbe T_VBE_COEFF 0x22 T_Vbe Table 51 Bit 6 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 T_Vbe< 0> DPS422 Pressure Measurement Calibration Coefficients Register Name Addr. Bit 7 COEFF_REG_1 0x26 C00 COEFF_REG_2 0x27 C00 COEFF_REG_3 0x28 C00 COEFF_REG_4 0x29 C10 COEFF_REG_5 0x2A C10 COEFF_REG_6 0x2B C01