Can not use read functions outside loop [ESP-8266]

[IMAN4K]

Hi.
I've recently test the library with the HTU21D & SI7021 to read the sensor data in some interval callback like this:

#include <ESP8266WiFi.h>
#include <Wire.h>
#include <HTU21D.h>
#include <Ticker.h>

#define D5 14
#define D6 12
#define D3 0
#define D4 2

static Ticker timer;

static HTU21D htu21d;

static void read() {
	if (!htu21d.batteryStatus()) {
		Serial.printf("HTU21D Battery: Not OK! \n");
	}

	float htu_h = htu21d.readHumidity();
	float htu_t = htu21d.readTemperature();
	Serial.printf("HTU21D(T): %f, HTU21D(RH): %f \n", htu_t, htu_h);
}

void setup() {
	Serial.begin(115200);

	WiFi.mode(WIFI_OFF);

	while (!htu21d.begin(D5, D6)) {
		Serial.print('.');
		delay(1000);
	}

	if (htu21d.batteryStatus()) {
		Serial.printf("\n HTU21D Battery: OK\n");
	}

	timer.attach(2.0, &read);
}

void loop() {

}

But inside the timer callback, sensors always report battery status as false and the humidity and temperature as error (255 == HTU21D_ERROR).

The situation for polling is not the same and sensors working properly! :

#include <ESP8266WiFi.h>
#include <Wire.h>
#include <HTU21D.h>

#define INTERVAL 2000
#define D5 14
#define D6 12
#define D3 0
#define D4 2

static HTU21D htu21d;

void setup() {
	Serial.begin(115200);

	WiFi.mode(WIFI_OFF);

	while (!htu21d.begin(D5, D6)) {
		Serial.print('.');
		delay(1000);
	}

	if (htu21d.batteryStatus()) {
		Serial.printf("\n HTU21D Battery: OK\n");
	}
}

void loop() {
	float htu_h = htu21d.readHumidity();
	float htu_t = htu21d.readTemperature();
	Serial.printf("HTU21D(T): %f, HTU21D(RH): %f \n", htu_t, htu_h);

	delay(INTERVAL);
}

No idea what's the problem here

Setup:

• Latest lib version
• Latest Arduino Git version
• ESP-8266(nodemcu)

Regards.

[IMAN4K]

After some debugging this is the error point in reading RH.
There should be a problem with Arduino TwoWire interface.

[IMAN4K]

This seems to be related to TwoWire interface.
No matter how many instance you create, you can just use one instance at a time to communicate with one I2C device !
More specifically, there are some global pin values which is set to twi_init(...) at every construction here