Library for the Northern Widget Walrus submersible pressure and temperature sensor. Based off of the TP-Downhole.
The Walrus is an encapsulated submersible pressure and temperature sensor intended for water-level or barometric monitoring.
Installation: included in NorthernWidget-libraries.
#include <Walrus_I2C.h>
Walrus sensor;
void setup() {
Serial.begin(9600);
if (!sensor.begin()) Serial.println(sensor.beginFailure()); // NotAnswering, NotSchema1, WrongName, OldFirmware
Serial.println(sensor.getHeader());
}
void loop() {
Serial.println(sensor.getString());
delay(1000);
}getString() takes one reading of both chips through the NW-Device-Specification handshake (updateMeasurements()): it triggers the device, waits for its reading counter, and prints pressure [mBar], the MCP9808 water temperature and the MS5803 temperature [°C], with -9999.00 where a reading failed. The getters return the stored reading: getPressure(), getTemperature(0) for the MCP9808 and getTemperature(1) for the MS5803.
One getString() can take several readings of each chip. setPressureReadings(n) sets how many the MS5803 takes, for pressure and its temperature. setTemperatureReadings(n) does the same for the MCP9808, for the water temperature. Each chip stores up to WALRUS_PRESSURE_CAPACITY or WALRUS_TEMPERATURE_CAPACITY readings: 16 by default, and you can define a larger one before the include. The values printed are then the means. For the spread, getPressureMean(), getPressureStd(), getPressureSterr() and getPressureMedian() read the stored readings. The same four exist for getTemperature…(0) and (1), and getPressureCount() and getTemperatureCount() say how many readings each chip holds. setPressureStats(true) or setTemperatureStats(true) adds std and sterr columns to getHeader() and getString(). To read one chip alone, call updateMeasurements(Walrus::MS5803) or updateMeasurements(Walrus::MCP9808). To log one row per reading to a file, call beginReadings(component, n), printHeader(out), then logReading(out) n times and endReadings(). Here out is any Print, such as an SdFat File or Serial.
Faults are there if you want them. faulted(chip) takes 0 for the MS5803 and 1 for the MCP9808. anyFault(), reportChip() and reportKind() summarise the last reading. printReport(Serial) prints the report as text, and reportNote() gives it as one word, such as MS5803NotAnswering, for a logger's note column. begin() refuses a device that is not Schema 1, is not a Walrus, or runs firmware older than patch WALRUS_FW_MIN_PATCH. beginFailure() tells you which. printStatus(out) prints one status line for a logger's status file (name, serial, hardware version, firmware patch and build commit from Page 0, this library's WALRUS_LIBRARY_VERSION and WALRUS_LIBRARY_COMMIT, the last report as code and note, Pages 0 to 2 in hex), for the logger to write with its timestamp whenever reportKind() is not zero. The two commits come from the NW-Build wrapper and are blank in an IDE build. Pages renumbered 2026-09-23 (spec 4c3b18d): calibration is Page 1 at 0x20, data Page 2 at 0x40. This version needs the NW_Core library and Walrus firmware patch 1 or later.
Full API reference: https://docs.northernwidget.com/Walrus_Library/