Portsdown 4 + 3.5" Waveshare Touch Screen

[G4MJW]

I'm making a second Portsdown 4, more compact and want to use a 3.5" Waveshare Touch Screen (and I already have one). I guess that I need to install some drivers as when I connected it nothing happened apart from the backlight came on. This Portsdown is working with the 7" official Touch Screen. I've read re-read the Portsdown Hardware and Screens pages in the Wiki but unless I missed something, didn't see how to get the 3.5" Waveshare to work! Help!

Steve

[radiogareth]

Fairly sure it's not supported on a PD4. Smallest is the DxRobot 5" unit which works well with touch. I found the 3.5 always needed a probe/pen/stylus.
Gareth

[G4MJW]

Hi Gareth . . . That might explain it. In the settings under display, there's only a choice of 5" or 7". In the wiki it mentions Limited Support for the Waveshre 3.5". Pity. My second 7" the touch has failed, so I will have to purchase something to continue the project.

Thanks forvthe info.

Steve

[G8GKQ]

The Portsdown 4 ONLY works with 800x480 pixel DSI-connected screens, as the graphics hardware that drives variable screen resolutions was dropped during the transition from Raspberry Pi 3 to Raspberry Pi 4.

It was an early design decision that the Portsdown 4 would not support GPIO-connected screens, so as to free up the pins for other peripherals.

Dave, G8GKQ

[G4MJW]

Thanks for the confirmation David.

Waveshare 3.5" back in the store now for some future project! Ill get my 2mtr PA (146.5MHz) finished off and then invest in the 5" recomended screen.

Thanks again

Steve/G4MJW

[G4MJW]

Gareth

I decided to get a DFrobot 5" DSI Screen for my OB /M unit . . . However, when searched I could not find any stock in the UK. So I gambled on an OSOYOO 5" DSI virtually same spec as the DFrobot. It arrived this morning and without delay I connected it to a new Raspi 4, White Sound dongle etc etc. As I had previous created 4a few back-up SD Cards, I was ready to go! It booted up quite rapidly and seemed faster than my Shack Portsdown-cum-Langstone. I tested every touch button on the screen and almost every menue item and it works every bit as good as the official 7" Pi touch screen. The display is sharp and very bright and if anything is a better better than the 7". How it compares to the DFrobot version, I may never know!

Steve/G4MJW

[radiogareth]

Useful to know of another compatible screen. The 5" is perfectly usable too
Gareth

[g0mjw]

How much QRM does it generate on 2m?

[G4MJW]

. . . Very little. It uses the dsi for data and 5V, so both LCD and Pi 4 are on one 5V (5.2) PSU. Pluto and everything else are on separate PSU's.I don't hear any carriers or digital noise on my 2mte SSB rig.

Steve/G4MJW