Multitouch Kernel driver about hyperpixel

[Gadgetoid]

I believe using the raw ADC values is the key to making a good driver, but you're right about ghosting. The trouble is that's the challenge- coming up with an algorithm, or touch recognition technique that takes it into account and compensates for it. The built-in two-touch recognition works, just about, but has some key weaknesses when recognising two touches that make gestures a little clumsy and make certain things - like the Pong demo and analog-stick spaceship demo I made for the official touchscreen - impossible.

As a tangent- the raw ADC values are extremely useful for triggering precisely placed controls. I managed to create a rough button driver that makes parts of the screen behave like a D-Pad and A/B buttons.

But I digress- I don't have any deep insight into how we'd solve the ghosting issue and recognise/track 2-4 touches with any degree of accuracy.

[procount]

I think I should walk before I run and concentrate on just creating a simple kernel driver, before I start looking at algorithms! But it's good background stuff.

(UPDATE: I found the pong and spaceship demos)

[Gadgetoid]

They are part of python-multitouch, which is for the official Raspberry Pi 7" touchscreen- https://github.com/pimoroni/python-multitouch

Since HyperPixel is the same resolution, they should look fine but - if memory serves me - do not work particularly well at all.

[procount]

I've added support for the Hyperpixel display to PINN.
https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=142574&p=1309584#p1309584
No touchscreen support yet, but I hope to add that later when I find a bit more time.

[procount]

@Gadgetoid - OK, I'm back on creating a kernel touchscreen driver for the Hyperpixel 3.2.
I'm making good progress now that my driver loads, detects the touchscreen is fitted and can read the touch positions.

Do you have any more information on the following registers:

0x6e: interrupt settings - 0 0 0 0 EN_INT INT_POL INT_MODE1 INT_MODE2
0x6f?: interrupt width
0x70: power mode 0000 <- IDLE PERIOD, 1 ALLOW SLEEP 00 <- POWER MODE

particularly the interrupt modes.

I see your python driver uses:
EN_INT = 1 (Enable Interrupt?)
INT_POL = 1 (Interrupt Polling?)
INT_MODE1 = 1 (Interrupt mode 1?)
INT_MODE2 = 0 (Interrupt mode 2?)
and polls the interrupt line. What clears the interrupt line? Is it when you read from registers 0x40 onwards?
Do you know how to set this up for proper interrupt mode?
What are the other interrupt modes it supports?
I guess you have no idea about 0x6f (interrupt width) as you already put a question mark against it.

I don't see the HP 3.2 on your shop anymore. Is it discontinued now the HP4 is available?