user37609: I found hundreds of questions about display not working with arduino.
However, no matter how trivial this looks like I am having the same problem I cannot understand by reading the other posts.
I have an Arduino micro connected to a display from the adafruit kit  
RGB LCD SHIELD KIT W/ 16X2 CHARACTER DISPLAY
I haven't been able to understand whether positive or negative, but I think from the picture is RGB positive.
I have connected everything as shown in the diagram in this page:
LCD "Hello World!"


Obviously changing the pins as I have 
RS at 8
E at 7
d4 = 12
d5 = 11
d6 = 10
d7 = 9;

The potentiometer changes the contrast, if I saturate it I can see the black boxes.
In the code put this as 
const int rs = 8, en = 7, d4 = 12, d5 = 11, d6 = 10, d7 = 9;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

I checked with the multimeter whether the soldering is good and it carries the signal at the end of the wires.
and the rest as the example in the link,
This is my mess (please ignore the other arduino and the thermocople which is not connected, the other orange wire goes to GND of the Arduino).

Any ideas that might help?

user30005: 
disconnect the E line, power up the system and adjust the contrast so you see 1 black bar on the first line;
reconnect the E line and see if your code is working.
go from there.


37609: <p>I found hundreds of questions about display not working with arduino.
However, no matter how trivial this looks like I am having the same problem I cannot understand by reading the other posts.</p>

<p>I have an Arduino micro connected to a display from the adafruit kit  </p>

<p>RGB LCD SHIELD KIT W/ 16X2 CHARACTER DISPLAY</p>

<p>I haven't been able to understand whether positive or negative, but I think from the picture is RGB positive.</p>

<p>I have connected everything as shown in the diagram in this page:</p>

<p><a href="https://www.arduino.cc/en/Tutorial/HelloWorld" rel="nofollow noreferrer">LCD "Hello World!"</a></p>

<p><a href="https://i.stack.imgur.com/koS2x.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/koS2x.png" alt="enter image description here"></a></p>

<p><a href="https://i.stack.imgur.com/7L1vz.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7L1vz.png" alt="enter image description here"></a></p>

<p>Obviously changing the pins as I have </p>

<pre><code>RS at 8
E at 7
d4 = 12
d5 = 11
d6 = 10
d7 = 9;
</code></pre>

<p>The potentiometer changes the contrast, if I saturate it I can see the black boxes.</p>

<p>In the code put this as </p>

<pre><code>const int rs = 8, en = 7, d4 = 12, d5 = 11, d6 = 10, d7 = 9;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
</code></pre>

<p>I checked with the multimeter whether the soldering is good and it carries the signal at the end of the wires.</p>

<p>and the rest as the example in the link,</p>

<p>This is my mess (please ignore the other arduino and the thermocople which is not connected, the other orange wire goes to GND of the Arduino).</p>

<p><a href="https://i.stack.imgur.com/rUJKd.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rUJKd.jpg" alt="enter image description here"></a></p>

<p>Any ideas that might help?</p>
 30005: <ol>
<li><p>disconnect the E line, power up the system and adjust the contrast so you see 1 black bar on the first line;</p></li>
<li><p>reconnect the E line and see if your code is working.</p></li>
<li><p>go from there.</p></li>
</ol>
