AVR Freaks

Remember when people spent a lot of effort optimizing their screen re-display algorithms because the "display" might be at the other end of a dialup link running at 1200bps or lower, and even the "local" terminals were limited to 9600?

I feel old...
 

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*       Ultra-hot screen management package              * 
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/***********************************************************-***** 


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                      |   XXXX     XXXX   | 
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                      \         X         / 
                       --\     XXX     /-- 
                        | |    XXX    | | 
                        | |           | | 
                        | I I I I I I I | 
                        |  I I I I I I  | 
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                          ************** 
                          *  BEWARE!!  * 
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                        All ye who enter here: 
                    Most of the code in this module 
                       is twisted beyond belief! 


                           Tread carefully. 


                    If you think you understand it, 
                              You Don't, 
                            So Look Again. 


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

I have never used a Nextion but understand that it accepts high-level graphics and text commands via the UART.

The Nextion has its own MCU which speaks to the hardware TFT controller chip.

I assume that most operations will operate nicely.   e.g. clearing the whole screen or drawing a circle.

But if you want to plot one pixel at a time it will be SLOW.

With any display program you have to obey simple rules to get the best performance:

1.  draw main screen with appropriate library methods

2.  update a minimal area when required

3.  keep track of any varying data so that you only update the screen when necessary

As mentioned in #13.   In the old days you would communicate with a mainframe computer via a 9600 baud RS232 Terminal.   

Yes,   a full screen editor was usable at 9600 baud.    This was due to libcurses.a that minimised the RS232 traffic when updating the Terminal screen.

Your Terminal might be connected via phone line with a 300 baud modem.    In which case full screen editor was not practical.

I can remember 1200/75 baud modems that were "almost usable" with MicroEmacs or other full screen editor.

David.

If you only need to TX at that speed it can be done over the SPI by folding the data over more than one byte. (and forget about the clk)

Probably not worth it for this, since there is no time to make other things unless they also is a "build in" part of the TX routine.

what kind of writes do you you need this high speed for ? 

Be more specific.    What do you actually want to see?

Plotting a single pixel at X, Y is fairly trivial.    You can plot 480 points in a short time.   i.e. a continuous line.

If you want the graph to scroll to the left as you plot each pixel it would mean re-plotting the whole graph as each new value arrives.

Of course,  a regular TFT can use its hardware scroll ability to take that work off your hands.

There are occasions when you need to take the "engineering view".   i.e. is it practical to implement with the available software and hardware?

If not,   think of another screen format approach.

David.

#21 make me a tad confused.

Does this mean that you only get 4 coordinates and from that you have to (re)draw the hole picture ?

if that is true how many bytes over the UART is a picture, and what else do you need to while updating the picture ?

and how often do you get new coordinates?  

+100

As I said in previous replies.   I do not have Nextion.  Nor studied the available Nextion commands.

If you want colour gradations.   Calculate X start and X end point,  start colour, end colour for a particular Y row.    Draw horizontal lines.    Angled lines are very expensive.

You have chosen something that is fairly difficult to do.    And it does not even look very impressive.

I strongly advise you to go back to your drawing board.    A nice cup of tea always helps.

Yes,  I know how to achieve your image on a regular dumb display with regular graphics library.

You can only work with the Nextion commands.

If you design your project well,  the Nextion could make impressive images.    With little low-level programming effort from you.

Most work will be done with a GUI on the PC.   i.e. using artistic and design skills rather than C, C++ programming skills.

David.

@ sparrow2

You can draw a filled rectangle efficiently on 99.9% TFT controllers.   A line is just a thin filled rectangle.   Pixels are sent in a block.

Drawing a series of angled lines requires plotting individual pixels.

Given an image,  it is the same number of pixels whether they are drawn in vertical strips, horizontal strips, diagonal strips.

The OP can try it for himself.   i.e. draw a filled triangle by horizontal strips or angled lines.

The same number of high level commands.   The Nextion firmware just has a harder job for angled lines and the underlying TFT controller requires many more instructions.

This applies to drawing the initial big trapezoid.

The main advice has always been: only update the minimal area.

Obviously this will tend to be thin triangular slivers.   Probably nothing more than a few angled lines. 

You can only use the Nextion methods that are available to you. 

@ Aser Elshawi

I suggest that you post on the Arduino.cc Displays Forum

There are Nextion experts who can help.

David.