Dennis,

> Not so easy to do when the "sections" are in completely separate
> processes

Which was/is the situation I'm thinking of (just imagine the OS accessing
the RTC, while another program is trying to set one of its alarms).

> {Wow -- those 2x16 LCDs have mutated since I last looked at them...
> I think I have one or two of the pure 8/4-bit parallel models

Thats the model I was referring to (salvaged a number of them).

The "I2C backpack" is actually just a dumb 8-bit I2C expander plus a
backlight-feeding transistor and a potmeter for the contrast.  In short,
everything you normally feed to the 4-bit interface of the LCD now has to go
over I2C - hence the previously mentioned checking of the LCD's busy line.

https://artofcircuits.com/product/i2c-io-expansion-interface-board-for-16x2-20x
2-character-lcd-modules-black

By the way: There seem to be two major variants: One using the lower 4 bits
of the expander for data, and the other (ofcourse) uses the higher bits.

Regards,
Rudy Wieser

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