using 2pcs of I2C "lcd modules"

Projects General Guidance
1

Up until now I only made some simple example projects and a robot.

For my first "real" project I would need 2 lcd modules 20x4 characters.
A lcd module that would match my needs would be the sainsmart 20x4 I2C lcd module. The specs mention "I2C Address: 0x3F or 0x27". So, is the adress changable of do you have one or the other? If I buy 2 of these, can I allways use both of them?
Other brands also mentioned these I2C adresses or mentione only one of them.
So what if I would like to use 4 of these LCD modules?

2

The address is usually set with solder bridges on the I2C backpack (small board on the back of the LCD).
Sainsmart doesn't give any info there. It seems that the bridges are on the back if the backpack (see pictures).
Another option (if you can't change the address) is to use an 8-channel I2C muxer (Adafruit).
Leo..

3

andyr74:
For my first "real" project I would need 2 lcd modules 20x4 characters.
A lcd module that would match my needs would be the sainsmart 20x4 I2C lcd module. The specs mention "I2C Address: 0x3F or 0x27". So, is the adress changable of do you have one or the other? If I buy 2 of these, can I allways use both of them?

I am not familiar with the Sainsmart module.

Have you asked Sainsmart about this, they sold you the display, they ought to be the ones providing you with support ?

4

Indeed, probably selectable through solder bridge, address select pin (tie to Vcc or GND to select the address), or even an on-board jumper. Check the data sheet on your specific device.

5

I didn't buy a module yet. I'm still in process of thinking everything out.
I would like to start with 2 lcd modules and maybe later when required expand to 4.

Any suggestions for LCD modules?

6

andyr74:
I would like to start with 2 lcd modules and maybe later when required expand to 4.

Then you're likely going to have problems with I2C addresses if you want that on a single Arduino/I2C bus.

7

wvmarle:
Then you're likely going to have problems with I2C addresses if you want that on a single Arduino/I2C bus.

I see that most I2C backpacks have three address solder bridges (eight devices), but not the Sainsmart one.
And see post#1. There is always the option of an 8-channel I2C muxer.
Leo..

8

I noticed the Sunfounder LCD module has 3 pins to set the adress.
So that one would be an option if I want to use more than one.

9

Aren't those I2C backpacks basically a PCF8574 on custom PCB? Then you'd have a choice of 8 I2C addresses.

10

wvmarle:
Aren't those I2C backpacks basically a PCF8574 on custom PCB? Then you'd have a choice of 8 I2C addresses.

Yes

11

I don't see any user accessable solder pads on the Sainsmart backpack.
Setting the address could involve scratching off the protective paint and re-routing traces.
Leo..

12

Wawa:
I don't see any user accessable solder pads on the Sainsmart backpack.
Setting the address could involve scratching off the protective paint and re-routing traces.
Leo..

For the sunfounder LCD module, I see (under the blue backlight regulator) 2 x 3 "solder holes" which should set the adress.
Can I just solder the holes togheter or should I use some wire to connect both?

13

The holes seem to be too far apart for a solder bridge.
I would use a small piece of U-shaped wire.
Leo..