Portsdown - HDMI output on Pi

[G8PEF]

A quick question for you all (my Portsdown is packed away at the moment, otherwise I'd probably be able to answer this myself)..

What, if anything, normally comes out of the HDMI socket of the Pi on a Portsdown?

Secondary query - can you output the Portsdown's built in test card to the HDMI socket (to use it as a test card source for something else, not whilst using the Portsdown to TX)?

73
John, G8PEF

[G8GKQ]

Hi John

The answer depends on your exact hardware and software specification. Using an RPi 3b with 3.5 inch touchscreen and the latest Portsdown Buster software, the HDMI output is active, but when you connect an HDMI screen it changes the resolution of the primary framebuffer to match the HDMI screen. This means that the text in the Portsdown Menus is displayed a lot smaller than normal, and all the test cards and camera images are displayed in small areas of the screen as they are sized for the standard Comp Vid frame buffer of 720x576.

Not sure what happens if you have a 7 inch screen, or if you use older Portsdown software. Probably no HDMI output.

Note that it would be possible to modify the testcards for full screen, you simply need to load appropriate size images, change the rendering settings and recompile the GUI application. It's not on my list of things to do as there are far cheaper sources for HDMI test signals.

Dave, G8GKQ

[G8PEF]

Thanks, Dave - I had a feeling it wouldn't be as simple as I was expecting

I have 2 Portsdowns in different stages of 'completion' - on with a 3.5" Waveshare screen (which was the. One I was hoping to press into service as a TC gen (in the absence of anything else to had at relatively short notice) - but that hasn't had a software update for a long time. I also have a 7" touchscreen version with a Lime Mini attached which had its software last updated about a month ago...

When you say that the TC and camera images are displayed in a small area of 'the screen', I presume that you mean that they won't fill the screen of the HDMI monitor?

I'll have to get round to the storage unit, next week, and dig both of them out and have a play about, I think.

73
John

[G8PEF]

Quick update, in case anyone else might benefit from the info...

I managed to find my 7" touchscreen version, and it appears to have stretch 201910230 software in it ( a bit older than. It thought?)

Connecting an HDMI monitor doesn't seem to affect the operation of the unit - and at boot time, both the 7" dispkay and the HDMI monitor display the big 'rainbow' square, but then the 7" continues on through the boot process until the main screen appears. The HDMI monitor, however, keeps displaying the 'rainbow' square at all times.

I couldn't find the 3.5" version, so I haven't investigated that yet.

73
John

[radiogareth]

On my bare-bones spare Stretch system, I've tried connecting a salvaged laptop screen and driver board. I found that it depends on when you power up the HDMI screen. Pre portsdown boot the laptop screen ends up small, after Portsdown boot I get a full sized screen and use it as my 'big screen' reference. Not touchscreen of course, but its another screen. Try different sequences and see what happens with your system.

Gareth

[G8PEF]

Thanks, Gareth, I'll give that a try - although whether it will help with my other experiment isn't clear, as I'm attempting to connect to a BMD switcher, rather than a monitor, and I don't think it'll be practical to power that up after the Portsdown, as it's part of a bigger system... And I'm not sure what communication happens between the switcher and the HDMI source at the time of connection (I'm presuming that it's some sort of HDMI-borne data exchange where the monitor tells the source what it can do that causes the Portsdown to reconfigure it's frame buffers? What would a switcher identify its capabilities as?)

73
John