Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 24 Jul 2023 18:08:00 +0200 | Subject | Re: [PATCH v2] auxdisplay: hd44780: move cursor home after clear display command |
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Hi Hugo,
On Sat, Jul 22, 2023 at 8:18 PM Hugo Villeneuve <hugo@hugovil.com> wrote: > From: Hugo Villeneuve <hvilleneuve@dimonoff.com> > > The DISPLAY_CLEAR command on the NewHaven NHD-0220DZW-AG5 display > does NOT change the DDRAM address to 00h (home position) like the > standard Hitachi HD44780 controller. As a consequence, the starting > position of the initial string LCD_INIT_TEXT is not guaranteed to be > at 0,0 depending on where the cursor was before the DISPLAY_CLEAR > command. > > Extract of DISPLAY_CLEAR command from datasheets of: > > Hitachi HD44780: > ... It then sets DDRAM address 0 into the address counter... > > NewHaven NHD-0220DZW-AG5 datasheet: > ... This instruction does not change the DDRAM Address > > Move the cursor home after sending DISPLAY_CLEAR command to support > non-standard LCDs. > > Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Thanks for your patch!
> --- a/drivers/auxdisplay/hd44780_common.c > +++ b/drivers/auxdisplay/hd44780_common.c > @@ -82,7 +82,15 @@ int hd44780_common_clear_display(struct charlcd *lcd) > hdc->write_cmd(hdc, LCD_CMD_DISPLAY_CLEAR); > /* datasheet says to wait 1,64 milliseconds */ > long_sleep(2); > - return 0; > + > + /* > + * The Hitachi HD44780 controller (and compatible ones) reset the DDRAM > + * address when executing the DISPLAY_CLEAR command, thus the > + * following call is not required. However, other controllers do not > + * (e.g. NewHaven NHD-0220DZW-AG5), thus move the cursor to home > + * unconditionally to support both. > + */ > + return hd44780_common_home(lcd);
Sorry, I haven't tested your patch yet, as my HD44780 display is currently not connected to any system.
Your patch LGTM, so Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Note that hd44780_common_home() calls hd44780_common_gotoxy(). According to the documentation, both HD44780U and NHD-0220DZW-AG5 support the Return Home command (0x02), so that could be a good alternative.
> } > EXPORT_SYMBOL_GPL(hd44780_common_clear_display);
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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