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Need an example of  SPI- TFT touchscreen for pocketbegle

chrischristian14

Hi, I am after adding a touchscreen TFT display to pocketbeagle.

I am already using I/O in C via iobb library, so I am not sure if using a TFT LCD with fbtft driver will conflict with iobb.

There are lot of LCDs available for RPi which should work for pocketbeagle but I am not sure

- How to install fbtft driver - as a module, not built with kernel, I mean use insmod after bootup

- How to modify the driver to tell it to use a specific SPI connectors and how to make sure the driver doesn't mess up existing I/O configuration.

- What are the steps to redirect Xfce environment to the LCD

- And of course the hardware connection.

 

Thanks

  • 0

    It seems pocketbeagle can't work with lcd because there is no GPU, so there is no way to have a full desktop environment on LCD.

    Should I use beaglebone instead ? I managed to get he VNC working and access the GUI desktop that way but, I really need LCD.

    Thanks

  • 0 in reply to chrischristian14

    Hi Chris,

     

    Are you sure about this, because it seems odd to me that a GPU is needed for a driver for SPI to read the normal framebuffer.

    I'm no expert on it either, so don't want to mislead you if you're really sure.

    Anyway, perhaps Pi is a better option if you're not completely sure how to go about it all with the BeagleBone, because there is a lot more information on the Pi on the Internet, than the BeagleBone (where often the information is outdated), so it's far more likely that you will find examples of SPI displays that work, for Pi.

    The BeagleBone Black  and PocketBeage etc don't have a lot of power compared to recent Pi models, and that could be useful if you want to run a full desktop (which is going to be low-res anyway, if you're using SPI). Pi has some more options for displays, that don't consume a lot of I/O ports either, unlike BeagleBone Black that uses up 24 or so pins for some display interfaces (not SPI).

  • 0 in reply to chrischristian14

    Hi,

    please look here:

    Home - Nextion

    Nextion displays may a solution. They have a controller and communicate via serial connections.

    But.... it is not cheap because you need something to realise your application.

    doing:

    1. on the Nextion website you'll find the editor with that you can create your images, buttons, menus, whatever.... (it's difficult to make movies, gif-animations may possible)

    2. create the communication protocols for the display and your controller - USB, or RS, or similar

    3. implement them and drive the display with your controller via a serial port.

     

    Gerald

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  • 0 in reply to shabaz

    Thanks Shabaz, unfortunately Pi is not an option because it is not an opensource hardware. If my project solves the problem it is intended to solve, I may go commercial and,

    I need opensource hardware then.

    I'll check  Nextion as suggested by Gerald, however this is not exactly what I wanted. It's not the same as getting a desktop environment.

    Cheers

  • 0 in reply to chrischristian14

    Hi  ,

     

    What is your plan?

    What do you want to do because, cheap and even cheaper and wanting to have the best at the same time cannot always be brought together.

     

    It is similar with my projects, which also contain rather smaller modules.

    At some point you will have reached the point where you really have to dig into your wallet in order for the project to succeed.

    So, the controller may also have to be different from what was planned at the beginning.

    Microchip has controllers in the 32-bit series that can also control graphic TFTs. Look there.

    This PIC32xxx can certainly also execute the lower processes at the same time.

     

    Nextion is on my mind because I've been looking for a TFT in the last few weeks and want the best for a cheap price.

    But I see it again and again, it usually ends in a contradiction.

    You really have to rethink and develop the project from scratch.

     

    You could find something else in the Amazon webshop.

    Other TFTs are also offered there, with graphics controllers on the circuit board.

    - For example for Arduino or something similar.

    But these are rather very small, 1, 2, 3 inches.

    And maybe they don't work because they're just "dummies" -  "CE" approved - China Emirates ". image

    - I haven't tested them, I don't trust them yet and I don't want to throw away any money. Therefore, I read everything carefully before I buy such a display ...

     

    Then there is also another manufacturer that is offered on Amazon, which makes similar TFT modules as Nextion, but eventually even more expensive.

    The disadvantage of both: A lot of effort for specially assembled modules.

    4D Systems or Electronic Assembly are also an option.

     

    The question is:

    how much money do you want to spend?

    How much graphics and moving graphics do you need?

    How much resolution, etc ...?

    Touch? ...

     

    Best Regards

    Gerald

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  • 0 in reply to geralds

    Hi Gerald,

    I am not looking for more than 4 inch display size and with minimum GUI, few buttons, one text box.

    Nextion has really bad review, so I am still looking around, though I don't like the approach as it renders the Linux GUI useless, but if I can't find anything else then

    buying a HMI LCD with touch is the way to go, I would want an LCD under $50 NZD (~$30-$40 USD). Not much graphic, maybe one or two logos.

    Proculus looks good but their GUI design software doesn't support Linux, it only works on Windows and I don't have access to Windows PC, I'll have to borrow one, again not preferable.

    I thought there must be something simple that I can easily get working with a simple C or pyhton script by sending bytes to I2C or SPI, like HD44780 based character LCDs, I don't expect it to be that simple but something that I can write drivers from scratch or just use a Linux kernel module.

    I am surprised to see how little information is available out there, when you try to dig deeper (driver, example etc.), there is simply nothing generic that one can use.

    Most of it is for RPi specific, nothing for generic Linux, e.g. Define I2C/SPI/UART in  so_and_so.h file, run make, "insmod" the .ko file, and this is the API.

    I was expecting that kind of information, but so far no luck. Basically there is no serial LCD product as such, it is only designed "for something", the drivers for which is bundled in Linux image, not as a separate lib.

     

    Thanks,

    Chris

  • 0 in reply to chrischristian14

    Hi Chris,

     

    Comments interspersed below:

     

    I am not looking for more than 4 inch display size and with minimum GUI, few buttons, one text box.

    In that case, there's no need to render the entire desktop, or to have a GPU. All you need to do is send instructions to draw buttons and text. That can be done with many SPI displays.

     

    Nextion has really bad review, so I am still looking around, though I don't like the approach as it renders the Linux GUI useless, but if I can't find anything else then

    buying a HMI LCD with touch is the way to go, I would want an LCD under $50 NZD (~$30-$40 USD). Not much graphic, maybe one or two logos.

    There's no Linux GUI as such. I think based on what it sounds like your requirement is, you may just need to render basic shapes and images and not require much in the way of animations, so you may not even need any driver and could do it all in user-space code (e.g. your own code, or example code downloaded from the web, in say C, to draw lines, boxes, send bytes from image arrays, all over SPI). No need to look at display drivers in Linux, or any other driver, other than normal SPI driver.

     

    Proculus looks good but their GUI design software doesn't support Linux, it only works on Windows and I don't have access to Windows PC, I'll have to borrow one, again not preferable.

    This conflicts a bit with your comment about needing minimal GUI. Is it possible to just sketch your GUI and convert to instructions like line, rectangle etc? If so, no GUI design software is needed.

    As an example (this is old code, not suggesting you use it, but just to give you an idea):

    BBB - Small OLED Graphic Display

    That page shows an example text menu in one of the photos, as well as other photos containing images etc., all done with no GUI library, and no GUI design software. The web page there shows how to connect it, and the source code is attached to that page, and also there is a github page with more code https://github.com/shabaz123/oled-SEPS525

    That should give you some ideas hopefully, but as mentioned, I wouldn't advise using this as-is, since it is a very old project and not been maintained. There will be much more information for Pi and SPI displays, and you may be able to port some of that to BeagleBone, but personally I wouldn't use the BeagleBone today unless I really had to. Open hardware is possible with many microcontrollers, especially if you don't absolutely need Linux (but I don't know your requirements, maybe you do need Linux).

     

    Most of it is for RPi specific, nothing for generic Linux, e.g. Define I2C/SPI/UART in  so_and_so.h file, run make, "insmod" the .ko file, and this is the API.

    I was expecting that kind of information, but so far no luck.

    You were looking for something that isn't needed if you're after just a simple GUI. No need for drivers and .ko files for a simple interface, you can do it all in user space, and use existing SPI driver. But it's true that you will find more information for Pi, and it may be more up-to-date too.

     

     

    image

     

     

     

     

  • 0 in reply to shabaz

    Hi Shabaz,

    That looks interesting, I'll  check it out. As for the Linux, I need wifi and USB and may also need database, all these are easy to work with on Linux and that's why I went for this.

    thanks, I'll try to post a link for my work here when I'll get it going, so may help someone else.

  • 0 in reply to chrischristian14

     

    Ok, so why not RPI? e.g. the nano version.

    I think this works with Linux, or does not?

     

    If not, is this a possibility?

    GMPUP-PBCAPE | Beagleboard.org Evaluation Kit for PocketBeagle | RS Components (rs-online.com)

    Grafic evalkit for pocketbeagle.

    or this:

    BB-CAPE-DISP-CT43 - Element14 | Farnell AT

    touch screen for BB

    For this display you'll find here more informations:

    4.3 LCD Display Cape for Beaglebone Board (Whit... | element14 | Design Center

     

    Gerald

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