Waveshare Pi Pico 2" display

[MikeTheGent]

Thanks for Nano GUI — it looks excellent. If I can get it working with my display I think it will be very useful.

I have a Waveshare 2” display I’d like to get working. Using the 1.44” configuration I get the aclock display in the centre of the screen. If I simply change the resolution to 320x240, I get garbage. I assume this means the display can be made to work, but there’s more to it than simply changing the resolution. Are you willing to give me some pointers?

Thanks, Mike

[peterhinch]

It's hard to support hardware I don't possess but I'll try. What display controller does it use? Which driver are you using to show the clock display?

[MikeTheGent]

I’ll post the details here tomorrow morning UK time. Mike Love one another. We don’t need more instructions; We need more examples. Bob Goff

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On 2 Sep 2022, 18:28 +0100, Peter Hinch ***@***.***>, wrote: It's hard to support hardware I don't possess but I'll try. What display controller does it use? Which driver are you using to show the clock display? — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you authored the thread.Message ID: ***@***.***>

[MikeTheGent]

The display is one of these https://www.waveshare.com/wiki/Pico-LCD-2 with ST7789V controller. Appears to be very similar to their 1.44" display, bigger with more pixels. Resolution is 320x240. I'm using the st7789.st7789_4bit driver.

[peterhinch]

There are two basic approaches: trial and error or doing a detailed study of the Waveshare example code.

When developing display drivers I always use this code to check: if the result is pixel perfect as described in the code comments then nano-gui will run. The simple nature of the graphic can indicate what is wrong if it doesn't display correctly.

I assume you're running in landscape mode and setting the width to 320. Perhaps you might post an image of the outcome of the above test with those args.

[MikeTheGent]

The first image is the unmodified code which is encouraging -- we've got the smaller screen in the centre of the 240x320 screen. But it's in the centre, not top left which explains what follows:

In the second image I have changed the width to 320, left the height at 135.
In the third image I have changed the height to 240.

The problem seems to be the offset of the display.

[MikeTheGent]

Just noticed the pattern that doesn't show up in photo 3, here's a better image. These small displays are hard to photograph with smart phone!

[peterhinch]

The first image has the correct orientation but is evidently offset in X and Y. I would start by trying to correct the offsets.

You'll need to play with the display constructor arg. To do this, comment out this check. The display arg is a 3-tuple, the default (which I assume you're using) is (0, 0, 0). The first two elements are X and Y offsets. Try passing small values and observe the effects. The third element should stay as 0 because the orientation is correct.

If you can get the image exactly located at the top left then you may be able to adjust height and width.

[MikeTheGent]

Thanks. I will experiment today.

[MikeTheGent]

Success! Based set up on setup_examples/st7789_pico_lcd_114.py, changed height & width. Changed drivers/st7789/st7789_4bit.py TDISPLAY to (0, 0, 1)

It works with TDISPLAY orientation. Many thanks for your help with this.

[peterhinch]

Excellent!

I am updating the driver to add a PI_PICO_LCD_2 tuple with value (0, 0, 1). I will also change the code so that an unexpected value of display merely prints a warning. This facilitates experimentation for further display types.

Please could you post a copy of your color_setup.py so that I can update the docs to include this very useful display.

[MikeTheGent]

Setup file:

color_setup.py.zip

[peterhinch]

I've now pushed an update documenting this driver here.

Thank you for your efforts in enabling me to support this useful (and remarkably inexpensive) display.

[MikeTheGent]

Thanks for letting me know. Pleased to have made a small contribution.

[JumpinJon]

Hi,

I have one of these displays bought from Pi Hut: https://thepihut.com/products/2-ips-lcd-display-for-raspberry-pi-pico
Initialising with PI_PICO_LCD_2 works fine, and I've got plenty of code working.

I note the Pi Hut page states Driver: ST7789VW and 65K RGB Colours; and indeed shows a thumbnail with a bright landscape image.
I wonder if you are able to add support for the additional capability? What can I provide in the way of diagnostics?

TIA

[peterhinch]

The display is 320*240 pixels. To support 65536 colors implies two bytes per pixel giving a buffer size of 153,600 bytes; this is quite unfeasible on the Pico. My drivers reduce the color information to four bits per pixel to overcome this.

The C drivers that use this display on the Pico use a different technique where commands are sent to the display avoiding the need for a frame buffer.

Drivers for nanogui and microgui are all framebuffer-based. This enables drivers to be minimal and also enables the GUI code to be device-independent. The answer therefore is a categorical no. If you want to display full-color pitcures you will need to use drivers not based on farmebuffers.

[JumpinJon]

Thank you for the detailed reply, that makes perfect sense.