How to use a LCD i2c (iic, i²c, whatever you call it) shield with an arduino due?

Hello,

I want to use a lcd i2c shield with an arduino due in Matlab/Simulink. The task sounds very simple: measure a temperature (LM35cz sensor) and show it on an lcd shield with an i2c interface. With the arduino software it's no problem, but I can't do it with Simulink.

I would appreciate a lot if somebody could help me with my problem.

Thanks in advance!

Sebastian

[Grant Sellers]

Hello Sebastian,

Could you provide some more information into what problem you are facing? Are you looking for a place to start? Hitting error messages along the way? Or getting unexpected behavior on the LCD screen?

With what I know now, I can simply suggest using the Simulink Support Package for Arduino Hardware. In that add-on, there will be blocks for I2C read and I2C write, which you can read for the temperature sensor and the LCD.

For sensors, we have a useful example of using this add-on here: https://www.mathworks.com/help/supportpkg/arduino/examples/read-temperature-from-an-i2c-based-sensor-using-arduino-hardware.html?searchHighlight=i2c%20simulink&s_tid=doc_srchtitle

For using LCDs, there are no specific examples, and so the implementation will depend on device. If it is an I2C device, then you should be able to write the correct registers to display information. However, I also know that often LCDs have custom libraries that abstract this further, and those libraries will not be supported.

[Sebastian Fischer]

Thank you very much for your reply!

More or less I'm looking for a place to start. I've already tested the i2c temperature sensor example. That has worked fine. But I don't know how to do with the LCD Shield (I2C Backpack). Do I understand you right, that I can work again with the Arduino Support package blocks "I2C Read/Write"? And is my assumption correct that I have to create a read/write block for every command and letter I want to print on the LCD display? Furthermore that looks quite complicated in the datasheet of the LCD shield. Here is a link to the datasheet of the LCD shield and a link for the HITACHI processor. I guess a example would be very helpful for me to see how i can write letters on the display.

I would appreciate a lot if you could help me further!

[Grant Sellers]

Of course, Sebastian, happy to help.

Yes, that is correct. You should still use the I2C Read and Write blocks.

You will not, however, have to create a new block for each command. The block is a general communication layer, and it takes data in at each simulation time step and transmits it over I2C.

If your device has multiple registers, you will need one block per register. However, from a quick look at your device, it seems to not have multiple registers.

As for the example, you said you are able to use the LCD with Arduino code, is that correct? If you are using a library for that application, you can look at the library code and figure out how it is communicating over I2C. That should be a helpful example for figuring out how to do the I2C communication.

[Sebastian Fischer]

Thank you for your answer.

Yes it's correct that I can use the LCD with Arduino code. I also tried to take a look in the libraries. Unfortunately I'm not familiar with C-Codes and I couldn't find the correct register adresses.

I tried to fix the problem now with the I2C Read/Write blocks as you said. And with a long time of studying the datasheet I could find the commands and the correct DDRAM adresses of the display.

The actual situiation is, that I know the slave device adresse of the LCD shield (0x27) and some commands. E.g. I want to write an "H". Then the command would be 1 0 0 1 0 0 1 0 0 0. When I take a look at the I2C write block in Simulink now, I have the slave device adress (0x27), the constant which I give in block ("H" --> dec.: 584). But I don't know in which register I have to write this constant value now. I tried to use the DDRAM adress but that did not work. In the attachement there is the small simulink model with the I2C write block where you can check what I did as well as the Libraries for the arduino software.

Thank you so much for your help! I really hope we can solve the problem.

[Grant Sellers]

Hi Sebastian,

It sounds like the issue here lies more in the inner-workings of communication with the LCD, rather than with how to do communication in Simulink. As a result, I think you may find additional help on a forum like Stack Exchange. You may also be able to contact the device manufacturer or the developer of the Arduino library for help.

If it comes back to an issue with Simulink, then this will be the place.