Adafruit QDTech Library conflicts with LOW state of digital out pins?

Other Hardware Displays
1

I have a tft display (1.8") (Adafruit QDTech Library) and a relay connected to an arduino nano. the relay is connected to pin 12, where it is activated when the pin is LOW.

The following code works, setting pin 12 to LOW (0V) in the loop, and activating the relay. However, if I activate the display - uncomment tft.init(); - pin 12 shows 3.7V in LOW.

Is this a software problem / conflict?

Thanks in advance!

// TFT DISPLAY //

#include <SPI.h>
#include "Adafruit_GFX.h" // Core graphics library
#include "Adafruit_QDTech.h" // Hardware-specific library

#define sclk 13 // Don't change
#define mosi 11 // Don't change
#define cs 9
#define dc 8
#define rst 7 // you can also connect this to the Arduino reset

Adafruit_QDTech tft = Adafruit_QDTech(cs, dc, rst); // Display-Bibliothek Setup

// RELAY
int relay = 12;

void setup() {

// RELAY: initialize the digital pin as an output.
pinMode(relay, OUTPUT);

//Display Setup
// tft.init();

}

void loop() {
digitalWrite(relay, LOW);
}

2

Can you try a different pin than 12?

Did you ask on the adafruit forum? They are great over there.

3

Using pin 10, it really works as expected. Thank you... :wink:

However, I think it is strange that the Adafruit QDTech Library occupies pin 12 like that.

4

NANO Pin 12 (MISO) is used in SPI communication...

I would have avoided pin 10 (SS) too. Same reason.