arduino-esp library for Sensirion SDP3x and SDP8xx series

ESP-IDF & Arduino friendly implementation of communication with Sensirion differential pressure sensors.

Compared to a general-purpose arduino library SDP3x-Arduino, it's:

1. a bit faster (158 vs 170 us). Benchmarks are measured for the 400kHz I2C clock frequency (Wire.setClock()).
2. not thread-safe. For thread-safe operations, use Arduino's Wire lib.
3. it has support for interrupt handlers (available for SDP3x sensors only). With interrupts, you can achieve reliable sensor updates at ~2100 Hz frequency. See the SDP3x_Interrupts demo.
4. ESP-IDF friendly: run this code either in Arduino or in your favourite ESP-IDF framework. For pure C implementation, refer to sdpsensor.c.
5. DataDrake's implementation has a bug in the reset function. It's fixed here.
6. Each function returns a descriptive error code defined in esp_err.h. To check for success, call if (err == ESP_OK) ....

I2C address

Typical I2C sensor addresses:

• SDP31 & SDP32: 0x21, 0x22, 0x23
• SDP8x0: 0x25
• SDP8x1: 0x26

Usage

See examples.

Serial output:

[  1021][I][sdpsensor.cpp:95] initI2C(): I2C0 line initialized
[  1021][I][sdpsensor.cpp:232] stopContinuous(): SDPSensor::stopContinuous ESP_OK
[  1043][I][sdpsensor.cpp:182] begin(): Initialized SDP31 500Pa sensor (PID=0x03010188)
[  1134][I][sdpsensor.cpp:200] begin(): SDP31 pressure scale: 60
[  1134][I][sdpsensor.cpp:219] startContinuous(): SDPSensor::startContinuous ESP_OK

[  2154][I][sdpsensor-esp-arduino.ino:32] loop(): raw pressure: 0, err code: ESP_OK
...

Resetting the sensor

If the sensor was working in a continuous mode, prior to executing any I2C commands, it ought to be reset by calling either the stopContinuous() or reset() function. Note, however, that the reset commands are received by all I2C peripherals connected to the same I2C line (port), because it employs the 0x00 address, which is the I2C general call address.

Capillary filter

To operate as a differential pressure sensor it must have a mechanical capillary filter attached to one of the ports. A low-pass frequency filter adapts to slowly changing atmospheric pressure, allowing mid- & high-frequency bands of differential pressure to be read from the other open port. Without the filter attached, the difference in pressure will be negligible.