I have a pretty standard 4 x 40 character LCD display that I'm trying
to use from my BBB.
I already got the BBB working OK with a 4 x 20 character display using
the connections and Python code described here:-
http://www.thebrokendesk.com/post/writing-to-an-lcd-screen-with-the-beaglebone-black/
An excellent article and I found it quite easy to follow and make it
all work.
However getting my 4 x 40 character display to work is proving
difficult. The 4 x 40 display is essentially two of the display
controllers in the 4 x 20 display working together. The hardware
interface is the same except that there are two 'Enable' lines, one
for each of the two controllers.
When I try to use my 4 x 40 display (initially with just 'Enable 1'
connected and the other tied to ground) I just get the first eight
characters and then a line of faded/ghost splodges. Try as I may I
can only get to display on the first line of the display and the first
8 characters.
If I ask for 5x10 bit characters instead of 5x8 then I get nothing at
all. If I set two-line mode I just get a few faded/ghost characters.
If I toggle the enable2 bit instead of enable1 leaving everything else
the same then I get nothing.
My 4 x 40 character display is like this one:-
http://www.buydisplay.com/default/40x4-lcd-module-datasheet-commands-arduino-pinout-hd44780-black-on-yg
There is documentation at the bottom of the page including some sample
code. The sample code is for an 8-bit microprocessor connected direct
to the LCD but, in the main, looks as if it does basically what my
code does except for some very odd loops but I think they may just be
'left overs'.
The manual for the 4 x 40 display itself doesn't say anything about
software for it or how the two enable bits need to be used. The
manual for the LCD controller is, of course, just for a single
controller, so doesn't deal with the dual-controller.
I think either:-
I have a faulty display or there is some subtle hardware
requirement that I'm not fulfilling.
or:-
There are some software requirements or extra command sequences
required to manage the two display drivers.
Does anyone know of any BBB code specifically for a 4 x 40 display?
Or even code for other SBCs for this sort of display. I can find
various references to such things but they're nearly always "how do I
adapt the 4 x 20 code to work with the 4 x 40 display" without any
actual code/changes.
Any/all ideas would be much appreciated.
--
Chris Green
ยท
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