Rick's b.log - 2020/08/07
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Uniroi UR071 7 inch display

Why?

Just as I was about to dismiss the Amazon app, I noticed there was something more interesting in the bit where "customers also took a butcher's at this barely-related hazarai". It was a stand-alone seven inch display. HDMI input, USB 5V power, and most importantly it was in a case. Originally something like €45, now €30, and Amazon promised to deliver it the following day if I ordered it in the next two hours.
I got up, thinking about it. It would be useful to have something HDMI native because all of my current displays (except the tiny one) are analogue, either driven natively from VGA or via a convertor.
It claimed a resolution of 1024×600. Not particularly large (and too small for managing proper HD) but I recall that the EeePC's display offered the same resolution, and I used that for numerous years.

I was stuck. Cold lemonade in hand, I made an agreement with myself. I'd go back to my room and I'd turn my phone on. If it was an odd minute, I'd leave it. If it was an even minute, I'd swipe the "Buy it now" thingy.

13h32.

Delivery

It arrived at half three in the afternoon. The delivery driver had his windows open. I asked him if he had air conditioning. He said yes, but he doesn't use it.
Even in the heat? I asked.
He told me that the heat, the weather, it was natural. Air conditioning was a completely fake environment.

You gotta respect a guy who drives around when it's a little over thirty seven (touching 100F) with his windows open because it's natural!

First impressions

There's a bit that protrudes out of the back that will contain the driver electronics, and doubles up as a stand.

Oh, I figured that 1024×600 pixels in something of that size should mean the pixels aren't obvious. They should be about six per millimetre; or sixty six per centimetre. That said, being at this price point I was expecting one of those lower-colour panels (64K or ~200K colour) and an LCD that had a restricted range of viewing angles, and if I was lucky, the top of the display might not look the same as the bottom (something the tablet suffers from, badly).

Hooking it up

The backup plan was easy. Dig up my old Pi 1B and hook that up. Only that wouldn't boot either. Huh? I pulled out the SD card and saw it was a 4GB card. Well, that'll be the reason. The card I used was an 8GB µSD in an adaptor (now in the Pi2), and before that a 2GB card. I rummaged around and found the 2GB card, and the Pi started up. The display was a mess, the right width but four screens down the height of the display, which slowly changed size until the panel blanked itself and started over again. Well, it was receiving a signal for a 1280×1024 display, so I'm impressed that it displayed anything at all.

I tweaked the CONFIG.TXT file as follows (using GPU scaling):

hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=87
hdmi_cvt 1024 600 60 6 0 0 0

The invalid mode '87' means it is specified manually. The CVT specifies a display of 1024×600 clocked at 60Hz, using 15:9 aspect, no margins, progressive scan, normal blanking.

I rebooted the Pi and saw the desktop in a square in the middle of the screen - it was still thinking it was 1280×1024. I changed mode to 1024×600, so there would be a 1:1 relationship between RISC OS pixels and monitor pixels, and this was the result:

The display is solid, stable, and actually looks pretty good. It is nowhere near as blue as it looks in the photo, that's because of flash photography (I have the shutters closed to help keep the heat out).
Yes, read that again. It's perfectly visible with a flash photo and the device used to take the photo being about 10cm away.
It's a pretty bright display.

Of course, the important thing is the viewing angle. There's nothing more frustating than basically not being able to enjoy something a display is showing because the display is rubbish. The reason I don't watch Netflix on the tablet is not because the processor is slow...

Here's a sharp angle picture of the display. You can see the colours are a lot warmer without flash. And you can see, no problems with viewing even at this angle.

Television?

It's been a while since I've watched TV. There's no BBC One. I'm guessing everything has been shuffled, as Sky do from time to time. I did get Judge Judy, so here's a photo of that. No flash, so you can better see the colours. And the lighter patches on her cloak aren't flattened colours due to the panel supporting a restricted set of colours. It looked the same on the LCD using the video convertor, so it's either studio lights or a bad low bitrate broadcast. Well... it is CBS Reality - it's probably a broadcast closer to horror channel than NHK World!

Summary

Criticism

The final point concerns the design. While I understand that it's going to be better to have this bit that sticks out of the back of the display rather than some sort of flimsy plastic stand, I do have reservations about the HDMI socket being at the back. This means that it will stick out even further. I'm not sure what would be a bigger problem, that a small LCD panel now needs a good 10cm of depth on a desk, or the possibility that it will get caught or nudged, potentially damaging the HDMI connector.
If you look at HDMI connectors (your Pi, the back of your TV...) they tend to be very fine with a lot of connections close together, that are packed into a chunky tight fitting plug, that is a close fit, in a socket that's just soldered to the board. They seem inherently fragile to me, and having it stick out of the back seems to be asking for trouble.

A look inside

Oh hell, this wouldn't be Rick's b.log if we didn't end up looking at some nerd porn. Here you go, the viscera:

Several things of interest at a glance. The first is that there is provision on the board for a model with an integrated USB touch panel. It's quite a large USB socket on the back. Given it's supposed to be a slave device, I wonder what sort of socket would be fitted? Surely it doesn't need to be anything larger than micro or mini USB?

Next, note the typo, "USB Touh". And note right beside it, it claims 800×480 pixel. Now if you look at the picture of the desktop above, there's no obvious evidence of down-scaling, the display is sharp (much sharper than the image resizing for my blog would indicate).
It appears to be exactly what it says on the all the documentation - 1024×600, so I'm guessing that there may have originally been a 7 inch 800×480 board, and it just got recycled with a better display panel. It's even possible that the 10 inch version has the same board inside it.

The device is powered by two ICs. The little one is an MK25040B which is a 512 byte SPI EEPROM which will provide configuration to the main chip, probably telling it what sort of display is attached.
The big chip is an HDMI to TTL/LVDS convertor, a Lontium LT8619B which can accept up to 4K@30Hz input, and output at up to 1080P@60Hz for FullHD panels, with numerous bit formats and colour mappings; clocked from a 25MHz crystal.

Your comments:

Sparky, 8th August 2020, 01:26

Thanks for confirmining it doesn't do interlaced. My sister purchased a BBC to DVI unit from J Kortink for me a while back but my moitor doesn't support interlaced so I can't use it. P / I is not something that seems to be advertised in the specs. Guess next monitor I get will have to be a TV!