So these IST chipsets really SUCK.
I have all the functionality, including dimming "working" but I still have not come up with a reliable bulletproof 4 bit initialization sequence for these broken chipsets.
Yes what I have will work from a coldstart/powerup, but it isn't reliable from a warmstart.
Yes I have tried the various example instruction sequences that they have provided, which BTW will not work once the device is already in 4 bit mode.
I have tried the normal/standard 4 bit initialization sequence which should work no matter what mode the chip is in including if the chip is in a state between nibbles in 4 bit mode.
But they simply have not properly implemented the hd44780 instruction set.
So far I know that there are issues with hd44780 clear display and function set.
They have also done some really REALLY dumb things like some of the default modes are wrong and/or don't work and have to be overriden. Things like the default memory to display positions is incorrect, and the internal timing must be changed.
Both of these require using table 2 extended instructions.
Oh and the display is off until you do table 2 extended command to turn on the power for the display pixels.
These are DUMB DUMB DUMB! things to do as it means that the device can never work with any code that expects to talk to a hd44780 chipset.
I'll have to start doing some deeper diving to try to figure out what they have done wrong in the function set instruction to try figure out if I can come up with an initialization sequence that really works reliably.
I fear that there may be no solution and that there likely will always be issues since the main thing is that they have extended the instruction set in ways that can break the function set instruction from working to go between 4 bit and 8 bit modes which is required to have a reliable initialization sequence.
There was a reason that bits 0 and 1 were ignored in the hd44780 function set instruction.
And those that use those bits for font selection bits are risking initialization issues.
--- bill