Help needed with I2C LCD + Arduino - DS-LCDD5

[jdev99]

I found a couple of these modules (a PIC18 daughter board on the back of a common 16x2 LCD)
It says in the datasheet that it can be controlled via I2C, but my skill level is too low to figure out how to do it.
Can somebody please give me advice on how to proceed?

The "I2C Scanner" sketch finds it, but the usual I2C-LCD libraries don't work on it.

Thank you.

[LateLesley]

HI,

Where you might be having difficulty with the standard libraries, is in the adressing of the display.

Most 16x2 displays have an address 0x27, and can be changed all the way down to 0x20.

But according to the manual on your display, the address is 0x28 - so you could need to check the sketches adresses are defined properly.

so where you would normally see

Code: [Select]

LiquidCrystal_I2C lcd(0x27, 16, 2);you would need to set the line up as 

Code: [Select]

LiquidCrystal_I2C lcd(0x28, 16, 2);
You can try going through this article here - https://create.arduino.cc/projecthub/akshayjoseph666/interface-i2c-16x2-lcd-with-arduino-uno-just-4-wires-273b24

But keep in mind to use the correct address for your display. Hopefully that will get you a bit further forward. I'm not sure the LiquidCrystal library will have the right codes to control that display. If not, you might have to set up I2C manually, and then send the codes directly to the display, as detailed the display manual on page 3/4.

I hope that helps.

Oh, and if you send characters to the display, and see nothing, check the contrast. It might be worth setting the display up to flash the cursor, then set the contrast, just to make sure it is displaying something.

You should be able to do that with the LCD Control Commands on page 4

[jdev99]

HI,

Where you might be having difficulty with the standard libraries, is in the adressing of the display.

Thank you for the quick reply. The "I2C scanner" did actually identify this module at address 0x14, which I then used in a test sketch. I think the problem is , as you mentioned, this module requires it's own way of addressing, that's why the usual libraries don't work. They mention how to do it on page 3 and 4, but that is where I get stuck, too complicated for me.
I will 1st have to learn more about the programming side it seems.

[DrG]

You have not said what you are attaching it to - Arduino UNO, PIC, ? EDIT: I see the title says Arduino - is that an UNO? Is it a 5v Arduino?

http://www.i-lcd.com/PDFs/Drivers/Technical%20data%20on%20DS-LCDD5%20Interface%20Module%20(IDS).pdf

Take a look at this data sheet which has examples of both RS232-type serial and I2C (this may be for an earlier version). You will NOT be able to use "standard" Arduino libraries as they are not intended for this module.

Start with making sure that you have the correct connections (power, GND, etc). You will need pullup resistors on the I2C.

The good news is that once you get things connected correctly, it is very easy to use...again, look at the document in the link and consider the examples and first make sure you have the connections correct. A picture and more info would make it easier to help you.

[LateLesley]

HI,

Where you might be having difficulty with the standard libraries, is in the adressing of the display.

Thank you for the quick reply. The "I2C scanner" did actually identify this module at address 0x14, which I then used in a test sketch. I think the problem is , as you mentioned, this module requires it's own way of addressing, that's why the usual libraries don't work. They mention how to do it on page 3 and 4, but that is where I get stuck, too complicated for me.
I will 1st have to learn more about the programming side it seems.

Well, the documentation is quite good. You can basically send the bytes directly.

You can do this with the Wire.h library, and just send each byte in order, as specified in the display manual.

Two links to help -
https://www.arduino.cc/en/reference/wire
https://www.arduino.cc/en/Tutorial/LibraryExamples/MasterWriter

In the second link, you are only concerned with the master side, and making sure you send to the correct address.
Also make sure you are using the correct pins for SCL and SDA on the arduino.

I'd try sending to 0x14 first, since that's what the i2c scan found. failing that, you can try it on 0x28. And just use the wire.write command to send each byte in order, as detailed in the display's manual. Also make sure you are using the correct pins for SCL and SDA on the arduino.

Try that, and see how you get on.

[jdev99]

I must be missing something basic, this is my setup and code:
Arduino UNO, SDA(A4), SCL(A5), 10k pullup resistors on each.
As mentioned before, the "I2C scanner" sketch , detects the module at 0x14, and according to the data sheet the address becomes 0x28 when writing to the module, if I understand correct.

Any other advice?

Code: [Select]

/*
I2C scanner. Scanning ...
Found address: 20 (0x14)
Done.
Found 1 device(s).


Example: (from data sheet)
To write ‘Hello’ to the display:
Byte 1 - 00101000 binary , 28 hex       // I2C address
Byte 2 - 00000000 binary , 00 hex       // Register address
Byte 3 - ‘H’ ASCII
Byte 4 - ‘e’ ASCII
Byte 5 - ‘l’ ASCII
Byte 6 - ‘l’ ASCII
Byte 7 - ‘o’ ASCII
*/


//************************************************//

// Include Arduino Wire library for I2C
#include <Wire.h>
 
// Define Slave I2C Address
#define SLAVE_ADDR 0x14                        // 7bit address = 0010100D, 0x14 hex



void setup () {
 
  Wire.begin();                                            // Initialize I2C communications as Master

 }

 

void loop () {
 
  // Write something to the Slave
  Wire.beginTransmission(0x14);                //  0x14  (SLAVE_ADDR)  0010100
  Wire.write(0x28);                                      //  (7bit SLAVE_ADDR + another 0 at LSB to enable write = 0x28    00101000
  Wire.write(0x00);                                      //  Register address  "0"
  Wire.write("1");                                         //  some text
  Wire.endTransmission();

  delay(500);
}



[DrG]

Before you jump to I2C, I would encourage you to do the following....This is how I would approach getting your boards with the display working.

First I would determine the board that I have. Is it exactly the one shown in the data sheet that you posted or is it more like the one that is shown in the data sheet that I linked? Can you not take a picture of the board and show it to us?

Next, I would determine which Arduino I was using. There are many of them and some work on 3.3v and some work on 5v. You need to know which you have because if it is a 3.3v Arduino, there are other things you need to consider.

For the sake of argument, I will ‘guess’ it is a 5v board, like an UNO and the board+display you have is one of the two seen in the datasheets.

First I would want to determine if the display is ‘alive’. To do this I would connect +5v and GND to the connectors on the board marked +5v and GND, respectively. If you have a 5V UNO, you have these connections available. Do not connect anything else to the Arduino or your board. Now, power up the Arduino and look at the display.

Find that little contrast adjustment on your board. Using a tiny screw driver (plastic one if you have one) turn that little potentiometer all the way to the left and then all the way to the right. If the board and display are alive, you should see bright rectangles on the display where the characters will later be seen at one of the extremes. Assuming, that you do, adjust the potentiometer to where you can just see the white rectangles.

The easiest test at this point is to connect SI (labelled on your board) to +5V. Then see if you get a version number on the display. If you got this far ok, but don’t see a message on the display, don’t worry about it as they may have taken that out in a later version.

If you got this far and all is well, then you need to figure out a couple of things. First, you will never get an Arduino library like the one that you were trying to use to work because they are not designed for your board. In fact, the purpose of the library is, in a very real sense, already present on the firmware on your board. Basically, it has its own library on board. It looks pretty clear that you can use either ttl-rs232 serial (which you can use the Arduino for) or I2C, (which you can also use the Arduino for).

But, jumping into I2C; not showing us any pictures of the board, not identifying the Arduino, not using pull-up resistors on the I2C lines and not making any attempt to verify that the board and the display are working first, all make it harder for us to help you.

[jdev99]

Should have mentioned, I got it working 100% with the 1 wire serial method they describe, but now want to see how it works with I2C, but their examples don't work the way I understand. 

[DrG]

Should have mentioned, I got it working 100% with the 1 wire serial method they describe, but now want to see how it works with I2C, but their examples don't work the way I understand. 

Ok, good and YES, that goes a long way in understanding where you are at. So, are you sure that you have the 10K pull-up resistors installed correctly on the I2C lines (remember, I have no idea how experienced you are). I would have used 1.8K or 2.2K but, let's go with your 10K unless you have the others handy.

With everything powered up, Re-run the I2C scanner and verify what it reports.

[DrG]

Assuming the same results, run this code and see if "Hello" appears on the display.

void setup () {
 
  Wire.begin();                                            // Initialize I2C communications as Master

 }

 

void loop () {
 
  // Write something to the Slave
  Wire.beginTransmission(0x28);                //  left shift reported address 0x14  (SLAVE_ADDR)  0010100
  Wire.write(0x28);                                       
  Wire.write(0x00);                                      edit: oops skip these lines
  Wire.write("Hello");                                         //  some text
  Wire.write(0);
  Wire.endTransmission();
  while(1);

edit; also, you probably don't need that last wire.write(0) as I think that the string is already null terminated.

[jdev99]

I replaced the 10k pullups with 1k8 resistors.
I2C scanner still reports address 0x14.
Changes to the code made no difference.

Looking at this example on page 4 of the pdf you linked:

Code: [Select]

/*The following code can be used on
the OOPic (II) to write ‘Hello’ to the display:

Dim LCD As New oi2c
*/
 
Sub Main ()
'Set the LCDD2 I2C address shifted right by 1 bit
LCD.Node = &h14 'Device address
LCD.Width = cv8bit 'Control Info is 1-byte
LCD.Mode = cv10bit 'I2C mode is 10-Bit

LCD.NoInc = cvTrue  'No increment
LCD.Location = 0 ‘Point to register R0
LCD = &h48 'Write ‘H’
LCD = &h65 'Write ‘e’
LCD = &h6C 'Write ‘l’
LCD = &h6C 'Write ‘l’
LCD = &h6F 'Write ‘o’
End Sub

It seems like they do use 0x14 as the device address and 1 bit for control info, making up 0x28 - maybe??   

[DrG]

 Try this.....

void setup () {
 
  Wire.begin();                                            // Initialize I2C communications as Master

 }


void loop () {
 
  // Write something to the Slave
  Wire.beginTransmission(0x28);                //  left shift reported address 0x14  (SLAVE_ADDR)  0010100
  Wire.write(0x00);                                 
  Wire.write("Hello");                                         //  some text
  Wire.endTransmission();
  while(1);

I think you need to point to the register first, hence the first write of 0
Do a clean power up before you try and make sure you have SDA and SCL connected correctly and the GND

If that does not work, try it with Wire.beginTransmission(0x14); 

...and which of the two boards - green or red do you have?

[DrG]

It seems like they do use 0x14 as the device address and 1 bit for control info, making up 0x28 - maybe??   

I went to 0x28 from 0x14 because I think they are using 8 bit addressing and the scanner is reporting the 7 bit address. It may be using 10 bit. See https://www.totalphase.com/support/articles/200349176-7-bit-8-bit-and-10-bit-I2C-Slave-Addressing#10bit, for example.

The LSB is 0/1 for W/R but the wire library knows about that.

You are close, but again, which board do you have?

[jdev99]

No, still not  working.
I noticed that they say in the manual that the serial baud rate must be1200-9600bps 57600bps

How do I set it in this case, or does it not matter with I2C?

[DrG]

No, still not  working.
I noticed that they say in the manual that the serial baud rate must be1200-9600bps.
How do I set it in this case, or does it not matter with I2C?

Do you mind saying which board you have?

[jdev99]

I use an Arduino UNO R3.

[DrG]

I use an Arduino UNO R3.

I got that. I mean the display board....which one do you have...is it red and just like the one shown in the datasheet that you attached, or is it green, like the one in the datasheet that I linked?

[jdev99]

Sorry, the Red board, exactly like the one from my data sheet.

[DrG]

Sorry, the Red board, exactly like the one from my data sheet.

OK, let's try this: Using the example from the red board data sheet...
To write the character ‘A’ to position 6 of
line 1 on a 16 x 2 type display:
Byte 1 - 00101000binary, 28hex
Byte 2 - 00000001binary, 01hex
Byte 3 - 134decimal, 86hex
Byte 1 - 00101000binary, 28hex
Byte 2 - 00000000binary, 00hex
Byte 3 - ‘A’ASCII


void setup () {
  Wire.begin();                           
 }


void loop () {
 
  Wire.beginTransmission(0x28);                        //  left shift reported address 0x14  (SLAVE_ADDR)  0010100
  Wire.write(0x01);                                           // R1 register select
  Wire.write(0x86);                                           // set cursor at the first position
  Wire.endTransmission();                                 // send the data and a stop

  delay(100);
  Wire.beginTransmission(0x28);                        //  left shift reported address 0x14  (SLAVE_ADDR)  0010100
  Wire.write(0x0);                                             // R0 register command
  Wire.write(0x41);                                           // ascii code for 'A'
  Wire.endTransmission();                                 // send the data and a stop
  while(1);
}

Try and run this code and see if you can get an 'A' on the screen. It is possible that the other code worked but was writing to a non-visible area of display RAM - maybe it doesn't initialize the way I would think.

If it does not work, try again using 0x14, i.e., Wire.beginTransmission(0x14);

There should not be a speed problem as the datasheet says the max I2C speed is 400kHz and your Arduino defaults to 100 kHz.

If you had a scope, it would help because we could look for ACKs

[jdev99]

Thank you for all advice and efforts so far, will try it again later. 

If you had a scope, it would help because we could look for ACKs

Man, I think this covid messed up my head and memory. I do have a Rigol DS1104Z with all  options installed, completely forgot about it.  
Thanks for the reminder.

Am a bit under the weather today, got a flu from somewhere, will look at it hopefully tomorrow again.
Joe

[DrG]

Thank you for all advice and efforts so far, will try it again later. 

If you had a scope, it would help because we could look for ACKs

Man, I think this covid messed up my head and memory. I do have a Rigol DS1104Z with all  options installed, completely forgot about it.  
Thanks for the reminder.

Am a bit under the weather today, got a flu from somewhere, will look at it hopefully tomorrow again.
Joe

That's understandable and I hope that you feel better.

I have been following your thread on the Arduino forum and I think you are getting pretty much the same approach - although always with 0x14.

The thinking behind that code that I last included is that the module does not do a 'normal' initialization which would leave the cursor at a visible location in RAM (i.e., the first position) so that writing a character to R0 results in the character being visible on the screen. This is far-fetched but  not so far-fetched as you might think because the board can accept multiple kinds of displays, i.e., 16x2, 20x2, 20x4 or 40x2. Still, a reach. I hope you will give it a try.

Other examples, using 0x14, should have worked and I noticed that trying one (from the other forum) using simple backlight control is also a good idea.

I think that putting a scope or a logic analyzer will quickly answer whether the address is responsive. It must be, because the scanner picked it up, but maybe something is way off.

That nobody can find an Arduino example is a bit odd.

The earlier version (the green board) gives instructions on how to change the I2C address, which is stored in NVM. It is possible that all the attempts actually did that inadvertently, but again, I assume that you re-ran the scanner. I wonder what else is stored in NVM and whether inadvertent corruption could be a problem.

I can't see anything obvious in the way of a jumper or an enable.

There is a sneaky suspicion that something silly is going on (like not getting the SDA/SCL connections right, but again, the scanner did something) and that is why I had hoped a nice pic would have been included (many eyes can be helpful). I assume that you have nothing else attached to the UNO for all of these tests.

Bottom line for me is that I don't know why what should have worked, did not work, especially since you said that you have been able to get it to work with the ttl-rs232.

I will keep thinking about it and let you know if I come up with something. In any event I hope that you will get it solved and will report back the how and why.

[jdev99]

So, after I "remembered" that I have an oscilloscope, I hooked it up and noticed that I don't receive an "acknowledge" from the module.

Then I played around with the clock speed, and found I do get an "acknowledge" if I set it between 16000kHz and 18000kHz with the "Wire.setClock" command. 

Then by mere coincidence, I found that text must got to R1 NOT R0 and control commands to R2 NOT R1. 
But I could not get any of the RGB commands to work.
I tried this on all 6 of the modules which I have, same results.
I will just stick to serial comms when I need to use any of these.

So, either the datasheet is wrong or the firmware in the module is flawed.
At least I learned a lot about the workings of I2C in the process, which my goal was.

Thank you for all advice. 
Joe

Working example code:

Code: [Select]


// Include Arduino Wire library for I2C
#include <Wire.h>
 
// Define Slave I2C Address
#define SLAVE_ADDR 0x14                      // 7bit address = 0010100D, 0x14h


void setup () {
 
 Wire.begin();                                    // Initialize I2C communications as Master
 Wire.setClock(16000);                            // only 16000 - 18000 work

//Clear display
 Wire.beginTransmission(0x14);
 Wire.write(0x02);
 Wire.write(0x01);
 Wire.endTransmission();

}

 

void loop () {


//Start print on line1, pos1
  Wire.beginTransmission(0x14);
  Wire.write(0x02);
  Wire.write(128);
  Wire.endTransmission();


 // Write something to the Slave
  Wire.beginTransmission(0x14);                       //  0x14  (SLAVE_ADDR)  0010100
  Wire.write(0x01);                                   //  Register address  "0"
  Wire.write("ABCDEFGHIJKLMNOP");                     //  some text
  Wire.endTransmission();


 delay(3000);

//Clear display
 Wire.beginTransmission(0x14);
 Wire.write(0x02);
 Wire.write(0x01);
 Wire.endTransmission();

//Start print on line2, pos1
  Wire.beginTransmission(0x14);
  Wire.write(0x02);
  Wire.write(192);
  Wire.endTransmission();

// Write something to the Slave
  Wire.beginTransmission(0x14);             
  Wire.write(0x01);                                     
  Wire.write("1234567890-=+*/@");       
  Wire.endTransmission();

delay(3000);

//Clear display
 Wire.beginTransmission(0x14);
 Wire.write(0x02);
 Wire.write(0x01);
 Wire.endTransmission();

}


[HB9EVI]

just for interest: what chip do you have on your i2c backpack?

[DrG]

So, after I "remembered" that I have an oscilloscope, I hooked it up and noticed that I don't receive an "acknowledge" from the module.

Then I played around with the clock speed, and found I do get an "acknowledge" if I set it between 16000kHz and 18000kHz with the "Wire.setClock" command. 

Then by mere coincidence, I found that text must got to R1 NOT R0 and control commands to R2 NOT R1. 
But I could not get any of the RGB commands to work.
I tried this on all 6 of the modules which I have, same results.
I will just stick to serial comms when I need to use any of these.

So, either the datasheet is wrong or the firmware in the module is flawed.
At least I learned a lot about the workings of I2C in the process, which my goal was.

Thank you for all advice. 
Joe

Working example code:
/--/

Good deal that you got some answers.

*very* surprising about the I2C speed needing to be in that small band (within limitations of wire set speed) - suspiciously surprising Did the wave forms still look squared at 100Khz? Different pullup value needed? That is weird and goes against what I thought was the resilience of I2C and speeds.

The R1 not R0 is pretty darn near silly. Thing is, that PIC chip can be programmed - it is meant to be accessed through that six pad interface on the board, so who knows if something strange was done to the batch that you have or ??

The important thing is that you got it figured out - good deal.

[jdev99]

I tried various pullups from 10k to 1k8, made no difference.
Above 4k7 the wave shape started to round at the top, but with the 1k8, nice and square.

Attached is a screen capture with 1k8, not the best resolution.
It shows the I2C address "0x14", the 1st write to "0x00" and the symbol "A" (0x41) and then ? means "no acknowledge".