I have three Nicla Sense ME boards, and on all of them the temperature is about 7.5 degrees too high, and the Humidity is about 22% too low. There is little difference between the native temperature reading and the compensated BSEC output. Adjusting the multiplier in the library to the corrected value also has little effect.
I've tried running in standalone mode, and as a shield on an Arduino MKR1010. Same result.
Attached is a plot from 24h, demonstrating a comparison against a BME280.
The code running on the Nicla Sense is below.
Does anyone have any suggestions? And has anyone tested the gas sensor accuracy against a benchmark? I have my doubts, given the strange temperature and humidity readings.
/*
*Script to set the NICLA to respond to a wire command and return bsec data
*/
#include "Nicla_System.h"
#include "Arduino_BHY2.h"
#include <Wire.h>
Sensor temp(SENSOR_ID_TEMP); //!!the library has a multiplier: https://community.bosch-sensortec.com/t5/MEMS-sensors-forum/Use-BSEC-with-BHI260AP-on-Arduino-Nicla-...
Sensor humi(SENSOR_ID_HUM );
Sensor baro(SENSOR_ID_BARO);
Sensor gas(SENSOR_ID_GAS);
SensorBSEC bsec(SENSOR_ID_BSEC_LEGACY); //it's critical to follow this tip https://community.bosch-sensortec.com/t5/MEMS-sensors-forum/BME688-Nicla-Sense-me-how-to-access-the-...
#define BAUD_RATE_SERIAL_DATA (115200) //To transfer bsec data https://community.bosch-sensortec.com/t5/MEMS-sensors-forum/Nicla-Sense-ME-I2C-Disconnecting-Bug/m-p...
int sampleInt = 5000;
unsigned long lastMillis = 0;
void setup()
{
//Serial.begin(115200);
Serial.begin(BAUD_RATE_SERIAL_DATA);
BHY2.begin();
temp.begin();
humi.begin();
baro.begin();
gas.begin();
bsec.begin();
nicla::begin();
nicla::leds.begin();
Wire.begin(8); // join i2c bus with address #8
Wire.onRequest(requestEvent); // register event
}
void loop()
{
int blueOn = 0;
//static auto lastMillis = millis();
// Update function should be continuously polled
BHY2.update(100);
if ((unsigned long)(millis() - lastMillis) > sampleInt) {
lastMillis = millis();
uint32_t eCO2 = bsec.co2_eq();
if (eCO2 < 800) nicla::leds.setColor(green);
if (eCO2 >= 800 && eCO2 < 1200) nicla::leds.setColor(yellow); // it's near green, could be optimized
if (eCO2 >= 1200) nicla::leds.setColor(red);
blueOn = 0;
}
if (millis() - lastMillis > 4000 & blueOn == 0) {
//blue means its waiting for a new query
nicla::leds.setColor(blue);
blueOn == 1;
}
}
void requestEvent() {
nicla::leds.setColor(magenta);
String output = bsec.toString();
char huh[131];
output.toCharArray(huh, 131);
Serial.print("Wire sending: ");
Serial.println(huh);
Wire.write(huh, 131); // respond with message of 131 bytes
// as expected by master
}
