Sunfounder I2C LCD2004 on UNO Wifi Rev2: no display

Other Hardware Displays
1

I have connected the LCD per Sunfounder docs.
Tried many different sketches and libraries.
When connected to the Uno, the display lights up and shows one line of shaded boxes, one blank line, another line of boxes and another blank line.

When I run Bill Perry's I2Cexpdiag, it gives this output:

********************************************************************
Serial Initialized
--------------------------------------------------------------------
I2CexpDiag - i2c LCD i/o expander backpack diagnostic tool
--------------------------------------------------------------------
hd44780 lib version: 1.3.2
--------------------------------------------------------------------
Reported Arduino Revision: 1.8.19
CPU ARCH: AVR - F_CPU: 16000000
--------------------------------------------------------------------
SDA digital pin: 20
SCL digital pin: 21
--------------------------------------------------------------------
Checking for required external I2C pull-up on SDA - YES
Checking for required external I2C pull-up on SCL - YES
Checking for I2C pins shorted together - Not Shorted
--------------------------------------------------------------------
Scanning i2c bus for devices..
 i2c device found at address 0x60
Total I2C devices found: 1
--------------------------------------------------------------------
Scanning i2c bus for all lcd displays (4 max)
LCD 0 begin() failed: -4
No working LCD devices

When I run an I2C address scanner it also shows me the address as 0x60.
However, for the PCF8574T chip, the I2C address range is: 0x20-0x27
QUESTION: How do I resolve this seeming inconsistency?

Help Mr. Wizard!
Thanks.
-- Paul

2

That tells you the contrast is set more-or-less correctly, but you are not initialising the display driver.

Bill's code says the PCF8574 is not (properly) connected to the display.

You do have it soldered, don't you? :thinking:

Please provide that link so we have some idea of what you have done. A photo or two might help.

4

Thanks for the quick reply.

The Uno Wifi Rev 2 and the LCD are both brand new.
No soldering has been done. Both are pristine just out of their packaging.

Here are two pics of the wiring:

LCD connections
LCD connections1920×2560 282 KB

Uno connections
Uno connections1920×1440 132 KB

-- Paul

5

The issue is resolved.
Sorry, but I've now redefined "noob".

I only just now realized that the Uno Wifi Rev 2 has separate SDA and SCL connectors.
When I use those, the LCD works fine.

Thanks.

6

For future reference, if you look at these lines of the I2CexpDiag output:

SDA digital pin: 20
SCL digital pin: 21

These lines show the Arduino pins used by the I2C bus signals.
If the SDA and SCL pins are also connected to the analog pins you would see:

SDA digital pin: 20 A4
SCL digital pin: 21 A5

So if you don't see A4 and A5 then those analog pins are not connected to the i2c pins.

--- bill

7

Thanks very much for the additional information.

-- Paul

8

Ah yes, I missed that.

That is because the "UNO WiFi Rev2" - with which I am not really familiar as I see no use for it (¶) - is in virtually no way related to the "standard" Arduino UNO as it uses completely different hardware with quite limited compatibility!

The concept of the Arduino IDE is to allow similar "C" code to be used on different systems, but the actual machine code has to match the different hardware.

( ¶ - For Wifi, the ESP8266 or ESP32 is generally substantially more useful and massively cheaper. :grin:)