[SOLVED] Problem with 16x2 display, no text?

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Naesstrom
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Posts: 23
Joined: 02 Jun 2017, 21:02

[SOLVED] Problem with 16x2 display, no text?

#1 Post by Naesstrom » 02 Jun 2017, 21:22

Hi

I'm trying to setup espeasy to use as a controller for my smart greenhouse and have connected it like this:
Image

The screen lights up but I'm not getting any text on it... ESPEasy seems to find it since it shows up in the I2C scan:
Image

And I have configured it like this in devices:
Image

Anyone have some ideas what might be wrong?
Last edited by Naesstrom on 03 Jun 2017, 08:53, edited 1 time in total.

Shardan
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Posts: 1156
Joined: 03 Sep 2016, 23:27
Location: Bielefeld / Germany

Re: Problem with 16x2 display, no text?

#2 Post by Shardan » 02 Jun 2017, 22:14

Hello,

at first i'd check if your display has pull-up resistors internally.
In this case the SCL and SDA is pulled to 5V - your nodeMCU will not like it.
You will have to use a level shifter then.

Disconnect SCL and SDA from the nodeMCU and check voltage at the display's SCL and SDA pins.
A simple digital voltmeter will do.
Another way to check this:
Disconnect SCL and SDA, switch off the display and use a digital multimeter to
check resistance between Vcc pin and the SCL/SDA pins. If you see a resistance below
20Kohm you most likely have internal pull up resistors.

If you don't even see the "ESP EASY" message at boot - did you try to adjust the contrast potentiometer?
(The blue cube with the white screw driver slot on the display interface board)
Turn it until you see white rectangles and then a bit back.

Regards
Shardan
Regards
Shardan

Naesstrom
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Posts: 23
Joined: 02 Jun 2017, 21:02

Re: Problem with 16x2 display, no text?

#3 Post by Naesstrom » 02 Jun 2017, 22:37

Shardan wrote: 02 Jun 2017, 22:14 If you don't even see the "ESP EASY" message at boot - did you try to adjust the contrast potentiometer?
(The blue cube with the white screw driver slot on the display interface board)
Turn it until you see white rectangles and then a bit back.

Regards
Shardan
Oh my godness, now I feel really stupid! I tried to change the contrast and suddenly I the text appeared... almost like magic :oops:
Thanks for helping a noob like me, tomorrow I'll install it in the greenhouse and try it out IRL :D

Any idea if it's possible to show the time since a switch was activated for example? using mqtt to turn on and off the relays from my Home-Assistant running an automotation to do it every other day

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