Unpull DOUT pin for ESPRESSIF boards

[Simonas0]

I've tested multiple ESP8266 modules and all fail to pull correct value from HX711 in range from 0x20000 to 0x30000 (instead it reads just a bit below 0x20000). When load cell is pushed hard enough, reading immediately jumps from a bit below 0x20000 to a bit above 0x30000.

#include <HX711.h>

HX711 loadcell;

void setup() {
  loadcell.begin(14, 12);
  Serial.begin(9600);
}

void loop() {
  Serial.println(loadcell.get_units());
}

Changing DOUT mode from INPUT_PULLUP to INPUT fixes the issue.
I've also tested multiple Arduino Nano modules and they all function properly regardless DOUT mode.

[nielsole]

INPUT_PULLUP was introduced by #138

[Simonas0]

I've "unpulled" DOUT only for Espressif boards.
Let me know if I need to do anything else in order to get this merged.

[bogde]

Thanks, I just merged it.