Review – Elecrow 5″ LCD

5″ LCD driven by ULX3S FPGA board

While this product is intended to be used with a Raspberry Pi, I bought it specifically to use with my FPGA board, having a HDMI (DVI) port on such a tiny board, just inspires a mobile build!

While there is a PI type connector on the board, you can simply use the LCD as a tiny HDMI monitor and it even works on a PI in that manner (you just won’t be able to utilise the touch screen). Unusually this device comes with a pin out diagram, so you can see what pins they are using and along side of the PI connector there are a set of complimentary solder pads which is a nice touch, it means I could implement a SPI connection with the FPGA and very probably use the touch screen if I wanted (XPT2046) – although I’m not too sure for my application (in the main likely retro emulation) it would be worth the bother…

Removing the PI connector would leave a board with a very low profile (less than 1cm by eye – there is a full sized HDMI connector on the back of the board) I’ll probably mount the LCD upside down so the HDMI connector is below the area I’d use for buttons… (oh oh I see an extended session with my 3d printer coming up…)

As far as compatibility is concerned it would seem you can almost throw any timings you like at this LCD and it will make a valiant attempt to display it, not often will you see the “no signal” screen saver, it will take a few seconds to display a new signal, but this is a small price to pay for protecting your display… It will just as happily display 1080 as 640 and handily it also accepts 800×480 too! (which is basically non standard in the world of HDMI timings…)

I’m currently working on a retro type Z80 system of my own architecture so I’ll be using 800×480 with each “retro pixel” being 4×4 pixels – this virtual 200×120 will give me a somewhat odd but useful 25×15 8×8 characters… this 375 byte screen memory will fit inside the fpga… I know, I know, I should be using a tiny bit of the perfectly good SDRAM for the whole memory map….

To be honest 640×480 looks fine and I could have used that but for edutainment reasons I decided to have a bash at a 33mhz dot clock (with 166 shift clock) and it basically just worked, as the Z80 core I’m using will push up to around 38mhz on the ULX3S I’m tempted just to use the dot clock as the main “system” clock…. (I dare say with some optimisation I could take it further but even 25mhz seems like cheating….)

So the only rub really is the cost – while the whole world can get these for around $30, here in the UK we get the privilege of paying £30… but on balance it comes well packaged (so likely undamaged!!) it works well and is obviously well thought out, so whether for your PI or even just as a tiny HDMI monitor or for your FPGA adventures…. probably worth it! and there is a chance you might be able to pick up one that previously enjoyed …

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