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Re: Convert 16x2 chars display to big TFT display

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Il 21/09/2021 15:44, Reinhardt Behm ha scritto:
> On Tue, 21 Sep 2021 12:31:54 +0200, pozz wrote:
> 
>> I have a CPU board that interfaces to a standard 16x2 chars display,
>> based on HD44780 controller.
>>
>> I'd like to replace this display with a full-color big TFT display,
>> maybe 10", but I can't change the firmware of the CPU (because I don't
>> have the source code and I can't rewrite it, because of cost and time).
>>
>> The simple idea is to create an interface between the current CPU board
>> and the TFT display. This interface should be able to detect the signals
>> from the CPU and that was directed to HD44780, interpret the
>> instructions (write CGRAM/DDRAM and so on) and write the same things to
>> the big TFT display.
>>
>> Of course, exactly the same texts will be written on TFT display (of
>> course with a bigger and visible font) and this is acceptable.
>>
>> So the MCU on the interface should be able to read 8 data bits, RS and
>> R/W signals syncronous to signal E.
>>
>> I'm thinking to configure E signal as an external interrupt on the
>> falling edge. In the interrupt, I read data bits, R/W and RS and decode
>> the instruction or data.
>>
>> Any suggestions? Maybe a similar code is already online.
> 
> I guess you don't need an interrupt. The signals to the 44780 are quite
> slow and well sequenced. So simple polling would do.

Are you sure? Enable cycle time could be 500ns at 5V, look at page 52 of 
datasheet[1].

> Beware that the E signal is high when data is valid. So I would look for
> the rising edge.

Are you sure? Look at Figure 25[1], data are valid at the falling edge 
of E signal.

[1] https://www.sparkfun.com/datasheets/LCD/HD44780.pdf

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Thread

Convert 16x2 chars display to big TFT display pozz <pozzugno@gmail.com> - 2021-09-21 12:31 +0200
  Re: Convert 16x2 chars display to big TFT display Reinhardt Behm <rbehm@hushmail.com> - 2021-09-21 13:44 +0000
    Re: Convert 16x2 chars display to big TFT display pozz <pozzugno@gmail.com> - 2021-09-21 16:01 +0200
      Re: Convert 16x2 chars display to big TFT display Reinhardt Behm <rbehm@hushmail.com> - 2021-09-21 15:07 +0000
      Re: Convert 16x2 chars display to big TFT display Stef <me@this.is.invalid> - 2021-09-21 17:09 +0200
        Re: Convert 16x2 chars display to big TFT display pozz <pozzugno@gmail.com> - 2021-09-21 18:48 +0200
  Re: Convert 16x2 chars display to big TFT display Don Y <blockedofcourse@foo.invalid> - 2021-09-21 19:34 -0700
    Re: Convert 16x2 chars display to big TFT display olaf <olaf@criseis.ruhr.de> - 2021-09-22 06:04 +0200
      Re: Convert 16x2 chars display to big TFT display Don Y <blockedofcourse@foo.invalid> - 2021-09-21 21:38 -0700
    Re: Convert 16x2 chars display to big TFT display pozz <pozzugno@gmail.com> - 2021-09-22 08:49 +0200
      Re: Convert 16x2 chars display to big TFT display Don Y <blockedofcourse@foo.invalid> - 2021-09-22 00:58 -0700
      Re: Convert 16x2 chars display to big TFT display Rick C <gnuarm.deletethisbit@gmail.com> - 2021-10-01 21:52 -0700
    Re: Convert 16x2 chars display to big TFT display Rick C <gnuarm.deletethisbit@gmail.com> - 2021-10-01 21:40 -0700
  Re: Convert 16x2 chars display to big TFT display Michael Schwingen <news-1513678000@discworld.dascon.de> - 2021-10-31 14:42 +0000

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