On Thu, 29 Oct 2020 11:39:54 -0700 (PDT), in
gmane.comp.hardware.beagleboard.user "Mark A. Yoder"
<mark.a.yoder-re5jqeeqqe8avxtiumw...@public.gmane.org> wrote:
>
>Is there a device tree for the hd44780 for a parallel interface?
>
I suspect the true parallel interface has become somewhat deprecated --
most later displays using that protocol have incorporated a sub-board that
does serial<>parallel (I2C or SPI, maybe even plain UART).
One problem is that the parallel mode supports TWO configurations:
8-bit parallel and 4-bit parallel. When you add in the other control
signals, you can easily consume 11 GPIOs (in 8-bit mode; 7 GPIOs in 4-bit).
Since the Beagle doesn't seem to expose a parallel load for GPIOs
(unlike the Arduino AVR and BASIC Stamp which expose PORTx registers), that
leads to 4/8 slow, single-bit, loads. cf:
https://groups.google.com/forum/#!topic/beagleboard/WZxfbaHipWA
Using a PRU might be feasible for this (though where the GPIOs are
exposed may not be contiguous to the bits in the PRU GPIO register).
--
Dennis L Bieber
--
For more options, visit http://beagleboard.org/discuss
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