Inky pHAT revisions

[pimoroni]

Inky pHAT revisions

[Gadgetoid]

There are myriad different resolution displays, different driver ICs and different configuration profiles (LUTs) for each display. The primary motivation for dropping v1 support from this library was to keep it simple, and uncomplicated by having to support multiple drivers. If you look over the v1 code you'll notice a really clunky approach to supporting multiple displays that Inky was attempting to reconsile.

Of course... e-ink manufacturers don't seem to give us a break! Indeed the feature/ssd1608 branch is intended to add support for a future revision. So that simplicity has somewhat melted away anyway.

There's nothing stopping the v1 code from being ported to this library using the same approach as the ssd1608, but the result probably wouldn't be very elegant.

We now populate an EEPROM on each Inky display in order to store information about the type and resolution of each display, but our current approach to reading and acting upon that EEPROM is suboptimal, too.

[DurandA]

Thanks for the extensive answer, this is appreciated.

May I ask what is the reference of the display of the v1, v2 and v3 red version? If I understand correctly, v2 and v3 use a different display but the same driver whilst v1 uses another driver. Also, can both v2 and v3 be used in monochrome ("black") mode for fast display?

[Gadgetoid]

I believe all the displays will do some kind of monochrome fast display, even the yellow/red displays can be driven slightly faster if you're willing to compromise on image quality. In all cases, though, they require a new LUT configuration and there's no documentation (that I'm aware of) to guide this process except the stuff I wrote after bashing my head against them for several weeks:

inky/library/inky/inky.py

Lines 108 to 156 in feb2303

	"""Inky Lookup Tables.
	These lookup tables comprise of two sets of values.
	The first set of values, formatted as binary, describe the voltages applied during the six update phases:
	Phase 0 Phase 1 Phase 2 Phase 3 Phase 4 Phase 5 Phase 6
	A B C D
	0b01001000, 0b10100000, 0b00010000, 0b00010000, 0b00010011, 0b00000000, 0b00000000, LUT0 - Black
	0b01001000, 0b10100000, 0b10000000, 0b00000000, 0b00000011, 0b00000000, 0b00000000, LUT1 - White
	0b00000000, 0b00000000, 0b00000000, 0b00000000, 0b00000000, 0b00000000, 0b00000000, NOT USED BY HARDWARE
	0b01001000, 0b10100101, 0b00000000, 0b10111011, 0b00000000, 0b00000000, 0b00000000, LUT3 - Yellow or Red
	0b00000000, 0b00000000, 0b00000000, 0b00000000, 0b00000000, 0b00000000, 0b00000000, LUT4 - VCOM
	There are seven possible phases, arranged horizontally, and only the phases with duration/repeat information
	(see below) are used during the update cycle.
	Each phase has four steps: A, B, C and D. Each step is represented by two binary bits and these bits can
	have one of four possible values representing the voltages to be applied. The default values follow:
	0b00: VSS or Ground
	0b01: VSH1 or 15V
	0b10: VSL or -15V
	0b11: VSH2 or 5.4V
	During each phase the Black, White and Yellow (or Red) stages are applied in turn, creating a voltage
	differential across each display pixel. This is what moves the physical ink particles in their suspension.
	The second set of values, formatted as hex, describe the duration of each step in a phase, and the number
	of times that phase should be repeated:
	Duration Repeat
	A B C D
	0x10, 0x04, 0x04, 0x04, 0x04, <-- Timings for Phase 0
	0x10, 0x04, 0x04, 0x04, 0x04, <-- Timings for Phase 1
	0x04, 0x08, 0x08, 0x10, 0x10, etc
	0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00,
	The duration and repeat parameters allow you to take a single sequence of A, B, C and D voltage values and
	transform them into a waveform that - effectively - wiggles the ink particles into the desired position.
	In all of our LUT definitions we use the first and second phases to flash/pulse and clear the display to
	mitigate image retention. The flashing effect is actually the ink particles being moved from the bottom to
	the top of the display repeatedly in an attempt to reset them back into a sensible resting position.
	"""

I'm afraid I've completely lost the plot in terms of which display driver/display part goes with which generation- I had a smattering of datasheets but no way to correlate them to a particular board. I juggle so many components and corresponding libraries. I can find out if engineering has records, though.

Sorry I can't be more immediately helpful.