two Arduinos accessing one four line display


So attempting to share a display over two Arduinos makes no sense at all. :cold_sweat:

Mostly the part about using two Arduinos makes no sense.

You use one Arduino. Your actual question if we pass over the "XY Problem", how do you combine the two codes for the two different tasks, into one. You need to read the instructions for posting and post the two codes in order to be advised on how you actually combine them. :grinning:

The answer to the hardware question: NO.

However, if you approach the kit designer in a constructive way, she may listen to your "improvements". Especially if you offer to do the development.

Be realistic. If an enhanced product would attract a smaller public it may not be commercially worthwhile.

"kits" appeal to the price sensitive customer.


So what is a "kit?"
(MOD EDIT). For what it seems to be, you should be able to do it with one Arduino - a small one. In the unlikely event that that is not possible, you can collect data with both Arduinos, and the one with no display sends its data via serial to the one that has, which can then send data from both to the display. It IS simple enough to do, but a solution only for the desperate and incompetent.

You might be doing newbies a favour, if you were a bit more forthcoming about this "kit", and who supplies it.

I read Displays, Zero, Due, Nano-Every Topics. They are all polite.

Some other Forum Topics can get bad tempered.

The best way to avoid misunderstanding is to post links to the actual hardware you are discussing.
Then you get constructive replies. (and the thread completes within minutes / hours)

Remember that Forum members come from a wide range of countries, languages, ages, technical knowledge...
If we don't have the necessary information, we have to make assumptions. (which can be wrong)


Not to add fuel to the fire, but most of the "mean" replies I read from this forum are from "older" members of the community.

Your assumption that "Nick" is a teenager is probably wrong.

I did get a good laugh out of this thread.

I did get a good laugh out of this thread.

Me too. But we eventually find out what the kit is, it has nothing to do with temperature or weather, and newbies need not worry. For, rather than the multi-purpose, multi-use Arduino kits commonly discussed on this forum, it is apparently a totally different single purpose commercial kit, like those one would buy from Radio Shack in 1962, long before Mr Nixon went to China and they started sending back ready-to-go instruments that were twice as good and half the price.
One would have thought that, with all that long and detailed experience with soldering irons, CROs, and exploding FETs, the OP would know when he has bought the wrong kit. But at least, yes, it IS possible to have one LCD with two Arduinos - which I seem to recall was the question.

And yes, I'm afraid you are right...... I soldered up my first project in about 1950, it had 2x 1Q5GTs and a lot of fahnestock clips. I had a great mentor up the road in ZL1AKB.

Probably one of the worst things about this discussion, is that - as best as I can find - we have not been provided any actual useful information.

Which is to say, the Website detailing the precious "kit"! :roll_eyes:

Indeed, hence my "apparently". But not to worry, they are all over the internet, and we are rather pompously told we don't need to know details like that. What strikes me as so funny is that, if they are all over the internet and, again apparently, have an Arduino programme on board, there is a chance that some smart, and experienced, cookie on this forum has got one, and knows all about hacking it .....(probably some snotty nosed teenager)

As an Electrical Engineer/Hardware Designer, I can say that Yes, two Arduinos can drive one display. Just need a bit of buffering to decide which one has control of the signals.
I only see 6 signals, so a simple 74HC541 between each Arduino and the control lines, with one or the other controlling their output enables, would do it. Even a simple manual toggle switch could do it.

Probably want to allow each to have control for a second or two to read the display before the other overwrote the display.

If the program for each did not write all positions when it had control tho, perhaps only updating areas or blocks that had changed, then the display could end up looking like a bunch of gibberish.

I think the other problem is knowing when to switch between the two so as not to lose data.
Can you do some monitoring of the first to see how often it updates?
If it is only updating once a second or once a minute, you could probably monitor for when a burst of data comes out (when the RS or the EN line goes active) and then switch over and output your data, giving control back in time for the other to send its data out again.

If it is using lines 1 and 2, and your new stuff is on 3 and 4, it might work out okay.

About the "kit"...
I'm still not sure what it is or how it is implemented terms of s/w.
If there is firmware in the kit that is based on Arduino s/w, the author is pretty much compelled to provide you the source code in order to comply with the LGPL 2.1+ licensing terms of some of the libraries he has likely used.
In particular LGPL 2.1 section 6(a)

It would be nice to see more information about this "kit".

-- -bill

I think the only think proven is that too many here are being close minded and literal and not open to new possibilities of change. Too many answers on the forum come across as rude, or as attacks on the poster, and serve to drive new questioners away. Mellow out, be open to someone one wanting to hack something for whatever unclear reason they might have, find a way to let new things happen and not put them down just because you yourself have never done something similar yourself or cannot see the usefulness of it.

Nick was given a short two day timeout to enable him to step back a little.

Anyone else want to be rude ?


Vandalising a post is also grounds for action but your point was addressed and you should have used the "REPORT TO MODERATOR" option rather than wreck your post.

If you still want to use the forum please abide by the rules as you can see we DO apply them equally regardless of who it is and how long they have been around.