I'm pretty sure it's I2C not Serial. The display itself may be classed as serial but the backpack that controls it is certainly I2C with those labels.

Problem 1: What's the I2C Address? Problem 2: What are the I2C commands for various tasks?

Searching the interweb it looks like the I2C address for this is 0x27 however that is not certain. Does anything on it say an I2C address or does it have a number like 0x27 stamped on it?

It looks similar to this one which is 0x27 (apparently!)

Unfortunately if it is not on 0x27 and we think it is then trying commands is going to be redundant.

However, let's assume 0x27 is correct. Now we need to know commands for the little blighter...

There are Arduino libraries for these, the LiquidCrystal library for example. Unfortunately I still do not understand enough about Arduino to be able to pick the library apart and find what needs to be sent to the I2C backpack, perhaps someone who has come from Arduino or can understand them can help on that?

Alternately, grab one of these and swap the nasty, unknown backpack for one which we know works or better still a Devantec LCD05-25-Image-Card from www.robot-electonics.co.uk (however they come in packs of 25, you may find single boards on ebay or could try asking robot electronics if they do them individually)

Looks like DJ beat me there

I2C can be chained, you are not limited to only 3 on the V4, you can chain up to 255 (I believe). I had 6 or so I2C devices on Melvin which come from the single I2C port on the V3.

I preferred I2C for two reasons...

1. They don't take up valuable digital ports
2. I had issues with serial causing some strange behaviour on the servos (I changed to I2C so never solved that issues and do not know what caused it - likely to have been user error).

If you want a good LCD which is UART serial I recommend Digole ones, they are pretty cheap and documented, I have written a few posts about them and have a lot of notes on them. Also Devantech are great LCDs however a little more pricey but very well documented.

So this is i2c only then. I'll inform the seller of that as he clearly misinformed me when he said it was both. Oh well, live and learn.

I thought the i2c ports may have been serial ports, but clarification is good so thanks for clearing that up.

The display I have doesn't have an address stamped anywhere on it, but I've pretty much given up on it now.

Rich, the robot electronics link didn't work, but found the site and had a look. Could you confirm if these displays are what I'm looking for before I order one? The one in the pic below is what I'm looking at.

Cheers.

Thats the one. I use the 4 line one in Melvin and couldn't be happier. Tony (@toymaker) recommended them to me so they must be good They are a little expensivr but worth the extra as they are easy to use.

Great, thanks for confirming. That'll teach me to go cheap . Yeah don't mind paying the extra beer tokens for something that's tested and recommended. I'll stick with the 2 line due to space restraints, but the 4 line is tempting.

Thanks for all of your assistance Rich, Richard and Dj. I've come away from this with a bit more knowledge (which is always a good thing) of using LCD displays with the EZ-B and ended up with a good resolution.

Thanks again guys.

Steve.

I learned the exact same way! I think we have all learned that lesson one way or another.

Hey @Steve G I figured I'd chime in and mention that I was working with that exact I2C LCD with the ez-bv4 yesterday. I had it responding to simple commands like turning the backlight on and blinking the cursor but I haven't had a chance to go too far with it.

I can confirm that the 0x27 I2C address does work but I would recommend a 1Kohm pullup on both the SDA and SCL lines if you'd like to use the LCD at a little bit of a distance away from the ez-b.

I may look into getting it working, but it will have to be on my own time. Are others interested in using these?

Thanks for responding Jeremie. I'm going to go with Rich's suggestion and recommendation of a new display, but I think it would be worth looking in to getting these cheapo displays to work if your willing to continue, as they are, Well... cheap, so others may be interested.

One question for you though, or for anyone else. Not being well versed in electronic circuits, can I ask, what does the pull up resistor do, especially in regards to the LCD's we're talking about? I did do a quick Google search but I'm still none the wiser.

Also, the displays that have been mention so far are 5v. Does anything need to be added to these when using the 3.3v i2c (unless that's what the pull ups are for)?