user52391: I have followed the instructions at https://www.arduino.cc/en/Tutorial/HelloWorld and have my LCD displaying some text. I've also connected the LED back light (LCD pins 15&16).
I wanted to replace the potentiometer used to set the contrast, with a connection to the DAC pin. It needs to be about 0.8V.
When I connect the contrast pin from the LCD to my DAC pin on my ESP32 board, it doesn't work, the contrast is too high. Using a volt meter, it measures about 2.5V.
If I disconnect the LCD contrast pin from my DAC pin, the voltage measured is 0.8V.
Any ideas or examples on how to control the LCD contrast using a DAC pin?
I wondered if I need to add a resistor or something.

user47766: The DAC in the ESP32 is ok for sourcing current but not so good at sinking current, and that is what you need. 
A amplifier set up as a voltage follower would work. 


52391: <p>I have followed the instructions at <a href="https://www.arduino.cc/en/Tutorial/HelloWorld" rel="nofollow noreferrer">https://www.arduino.cc/en/Tutorial/HelloWorld</a> and have my LCD displaying some text. I've also connected the LED back light (LCD pins 15&amp;16).</p>

<p>I wanted to replace the potentiometer used to set the contrast, with a connection to the DAC pin. It needs to be about 0.8V.</p>

<p>When I connect the contrast pin from the LCD to my DAC pin on my ESP32 board, it doesn't work, the contrast is too high. Using a volt meter, it measures about 2.5V.</p>

<p>If I disconnect the LCD contrast pin from my DAC pin, the voltage measured is 0.8V.</p>

<p>Any ideas or examples on how to control the LCD contrast using a DAC pin?</p>

<p>I wondered if I need to add a resistor or something.</p>
 47766: <p>The DAC in the ESP32 is ok for sourcing current but not so good at sinking current, and that is what you need. </p>

<p>A amplifier set up as a voltage follower would work. </p>

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