Messages in this thread | | | From | David Reaver <> | Subject | Re: [PATCH] auxdisplay: hd44780: move cursor home after clear display command | Date | Sat, 22 Jul 2023 07:46:59 -0700 |
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poeschel@lemonage.de writes:
> Am 2023-07-06 21:49, schrieb Hugo Villeneuve: >> On Thu, 6 Jul 2023 21:33:05 +0200 >> Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote: >> >>> On Thu, Jul 6, 2023 at 8:51 PM Hugo Villeneuve <hugo@hugovil.com> wrote: >>> > >>> > The "clear display" 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 clear display >>> > command. >>> > >>> > Extract of CLEAR_DISPLAY 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 clear display command to support >>> > non-standard LCDs. >>> > >>> > Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com> >>> Thanks! Sounds good to me, as long the extra command does not >>> introduce some issue with the actual HD44780 -- can we double-check >>> the HD44780 still works as expected? >>> Cc'ing Lars and Geert since they may be able to give it a quick test. >> Hi Miguel, >> I do not have a standard Hitachi controller to test it on, so lets wait >> for feedback from Lars and Geert or others. > > Sorry guys, > I do not have access to the relevant hardware anymore. I am CC'ing Christian, > who has the relevant hardware and maybe he can help testing the patch. > Christian is on vacation up until mid august, so we have to wait a bit more > for someone able to test this. > > BTW: The displays I did the work back then on were for sure not genuine > Hitachi ones either. > I do not see, that the little patch should do any harm. > > Regards, > Lars
I was actually hooking up a 16x2 HD44780 on my BeagleBone Black last night before I came across this patch, so I was able to test this. It works fine for me. I tested with:
$ printf '\f' > /dev/lcd $ printf 'Hello\nWorld!\n' > /dev/lcd $ printf '\x1b[LR' > /dev/lcd $ printf '\x1b[LR' > /dev/lcd $ printf '\x1b[LR' > /dev/lcd $ printf '\f' > /dev/lcd $ printf 'Goodbye\nWorld!\n' > /dev/lcd
As expected, "Goodbye World!" was correctly placed left-aligned on the display, split over both lines. Let me know if there is something else you would like me to do to test this!
Tested-by: David Reaver <me@davidreaver.com>
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