I think you have it nailed. It's why the mjkdz backpacks need a
different software initialization. Based on what I have read the mjkdz
backpacks wire to the lcd pinouts differently than the other backpacks.
The software apparently needs to know about that difference.
On Tue, 10 Apr 2018 09:02:23 -0700
"Jerry Gaffke via Groups.Io" <firstname.lastname@example.org> wrote:
I think that list of pins describes the interface between the PCF8574
i2c chip on the backpack into the parallel interface of the LCD
display. Nothing to do with pins on our Nano, all the Nano sees is
the SDA and SCL pins for the i2c bus that is shared between the i2c
display and the si5351.
The parallel interface into an lcd requires 4 parallel data lines,
and they are used for both read and write.
On Tue, Apr 10, 2018 at 08:56 am, Jack Purdum wrote:
It appears that most of those extra pins are for read/write
capability, and most of the BITX displays don't use software that
reads the display. Also, since most of those use pins 2 and 3, they
would kill the ability to use external interrupts on the rig. Since
I use external interrupts for tuning, such an I2C display for my
projects would be a bad choice. They probably are fine for projects
that don't use external interrupts. Personally, I'd look for
displays that only require the device address and the row/column