lerner
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Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 2:27 am

I know that there is a lot of demarcation between RasPies and Arduinos for projects.

I have an Arduino clock but, I want a better one.
As in more features.

Alas the Arduino's memory puts a stop to that as I run out of usable memory too quickly on that.

So the RasPi is an option.

This is the display I am wanting to use:

https://www.adafruit.com/product/498

Basic LCD display. 20 x 4 lines.

I know it won't just "plug and play" with the pins.

I am using Node-Red on the Pie to do things and will use it for this also.

There is a node which allows talking to a hat with a LCD screen, so that part isn't impossible.

So with that in mind, I was wondering if - accepting I will have to make a "cable" (jumper leads) between the Pie and the display - would it work?

Thanks much in advance.

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mooblie
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 5:32 am

Seems very expensive. Is the “rgb” backlight facility essential for you? If not, such displays cost about 7 GBP - including an I2C interface that gives your a four- or five- wire interface to the Pi. No hat needed.

https://www.ebay.co.uk/itm/With-Without ... Swva9dJwwU

lerner
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 5:37 am

Thanks.

I am preferring 20 x 4. 16 x 2 is just too small.

RGB back light.... Looks good and can be used for other things too.

Am looking now.

lerner
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 5:48 am

mooblie wrote:
Thu Jul 23, 2020 5:32 am
Seems very expensive. Is the “rgb” backlight facility essential for you? If not, such displays cost about 7 GBP - including an I2C interface that gives your a four- or five- wire interface to the Pi. No hat needed.

https://www.ebay.co.uk/itm/With-Without ... Swva9dJwwU
Oh love the ..... avatar Cute.

(Today is not my day)

I shall have to look harder, but I am not seeing the "RasPi compatible" part, and I would like the RGB light part.

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mooblie
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 6:23 am

This one says Pi compatible, but they all are. They’re all the same devices, including that I2C module on the back. You can select 16x2 or 20x4 in the item selection menu on eBay:

https://www.ebay.co.uk/itm/LCD-I2C-Disp ... Sw3b9cozQF

Picture of the I2C module on the back of the 20x4 LCD module you need:

https://i.ebayimg.com/images/g/9XkAAOSw ... -l1600.jpg
Last edited by mooblie on Thu Jul 23, 2020 6:28 am, edited 2 times in total.

lerner
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 6:27 am

Again, thanks.

I'll keep looking and see if I can find one with RGB lighting.

Another thought:

Ok, so I'm guessing it is that board which does the magic needed.

Couldn't I then buy one of them and get a "bare" 20x4 RGB display and plug it onto it and .... all working?
Yeah, ok the RGB may be tricky. But I am just thinking aloud.

This is the controller - yes?

https://www.banggood.com/RobotDyn-I2C-S ... mds=search

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mooblie
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 11:48 am

Yes, that looks like the I2C controller - it's a common part. Available cheaper on eBay, but I don't know where you are:

https://www.ebay.co.uk/itm/I2C-1602-LCD ... Sw02Vc3NdS

It drives either the 16x2 or 20x4 LCD, and I guess could be hooked up to an LCD with an RGB backlight (if you can buy that LCD separately) - but I don't know how/if you can control the backlight colour. You can certainly control the backlight on/off through software with that I2C interface.

lerner
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 12:42 pm

The display at which I am looking has separate RGB inputs for the backlight.

I am still looking/studying it.

This is going to be a big project if I build it, so I want to be sure.

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scruss
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 1:46 pm

Looks like Adafruit has discontinued their RGB 20x4 display. It was a 5V part so interfacing it to a Raspberry Pi was more fiddly. It did just work as an I²C device, but with two additional PWM channels for the green and blue backlight LEDs.

What isn't discontinued is SparkFun's 20x4 SerLCD - Black on RGB 3.3V. This is more compatible with the Raspberry Pi's 3.3 V logic, and you can also talk to it through UART serial (simple!) or SPI in addition to I²C. I don't think it uses a protocol compatible with the 1602 I²C LCD controllers, though, but SparkFun are usually very good with their documentation.

The SparkFun display is black on RGB, while Adafruit's was RGB on black, if that matters.
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lerner
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 10:11 pm

Thanks.

Adafruit had a positive and negative RGB LCD.

But thanks, that really helps I think. The levels are a definite help.

I'm not sure which would be better, using the I2C, or SPI, or direct wiring to the GPIO pins.

I have an old PiFace CAD hat and am not sure if it is I2C or direct wired. But that is the way I would go as I have a node for Node-Red which talks to that and so I am thinking a lot of the comms work would already be done.

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scruss
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 10:36 pm

CAD hat? Wossat? Link please. If it has an alphanumeric display, it's probably I²C
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lerner
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 10:50 pm

It is a 16x2 LCD hat with a few buttons.

It was called a PiFace CAD hat, but seems to be very hard to find info on nowadays.

Seems I am not allowed to add PDF files.

Here's a link which uses the board:

http://www.piface.org.uk/products/pifac ... display_2/

So if it uses SPI, then I get an SPI "hat" (board) for the RasPi and connect it between the Pi and the display and I should be able to use the node in Node-Red which talks to that hat.

I had to modify the code a bit as it didn't support character positioning, but that wasn't too difficult.

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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 11:44 pm

scruss wrote:
Thu Jul 23, 2020 10:36 pm
CAD hat? Wossat? Link please. If it has an alphanumeric display, it's probably I²C
The PiFace CAD uses a MCP23S17 SPI chip.

https://www.element14.com/community/peo ... -tear-down (it includes a roughly drawn schematic).
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lerner
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Re: Asking about compatability for a project I have in mind.

Thu Jul 23, 2020 11:56 pm

Hi Dougie,

I am only asking, there is no malice behind it:

This is looking good, but I am still not 100% sure:

https://core-electronics.com.au/sparkfu ... -3-3v.html
Which is great.
Would this be compatible with the hat/LCD?
https://core-electronics.com.au/i2c-spi ... kpack.html

I know the prices are not the best, but just to establish a list of things which would work together.

I have one of those "PiFace CAD" boards and as said, I can talk to it from Node-Red.
I had to modify the node to give the ability to position the cursor where needed.

So given I am not as up to speed with things as I would like, are the two boards mentioned the right ones?

Only asking.
Thanks in advance.

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Re: Asking about compatability for a project I have in mind.

Fri Jul 24, 2020 6:48 am

lerner wrote:
Thu Jul 23, 2020 11:56 pm

https://core-electronics.com.au/sparkfu ... -3-3v.html
Which is great.
Would this be compatible with the hat/LCD?
https://core-electronics.com.au/i2c-spi ... kpack.html
They're not going to make a HAT and won't work with a PiFaceCAD (because it blocks lots of header pins). First one should just work. Second one needs wiring to SIX gpio pins or with a PCF8754 you can drive it from I2C.

I've never used a 20x4 LCD but they're basically a HD44780 16x2 with a larger display RAM on them. I don't have any code to drive the first one (but it's not hard to drive HD44780s).

I've got code to run all sorts of LCDs at: https://github.com/DougieLawson/Raspber ... nified_LCD
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lerner
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Re: Asking about compatability for a project I have in mind.

Fri Jul 24, 2020 7:08 am

Thanks.

Progress has been made.

The PiFace CAD board is a bit painful to use as it does block all other GPIO pins.

But anyway.....

So that SPI driver will talk to the display and also the RasPi, that's a good thing.

Ok, I need a small "cable" to be made. That isn't a problem.

Moving to next stage.

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