LCD panel via pmod port

[glenalec]

I am wondering if, specifically for the Arty Artix-7, one of the pmod ports could theoretically be configured to carry enough data to drive a 1024x600x18-bit LCD at 24fps or greater, preferably on an LVDS interface.

[D@n]

@glenalec,

Feel free to surprise me, but ... I can't think of anyway you could do that without another device in the middle to handle the video.

Dan

[D@n]

@glenalec,

Is this the sort of device you are looking at?  I found it from this adafruit page.

Dan

[glenalec]

More like this or this. Direct LVDS drive, rather than via a HDMI-to-lvds converter.

If I end up having to go the HDMI route, I can use a Arty Z7, but I am not sure at this stage I have a use for the embedded ARM core.

My understanding is that pmod is really intended for low-speed I/O but I have seen a few mentions around the 'web of getting faster (specifically LVDS) data over specific ports of specific boards with a string of caveats.

[D@n]

@glenalec,

I'm looking through a specification I found via Google based upon your first, but ... I'm just not finding what I would need to definitively answer your question.  I was expecting that the data rate would've kept your from this--hence my initial answer.  So ... I went looking through the spec to find the highest data rate that you would be placing across the PMod port.  The spec suggests on page 15 that this might be less than 57MHz.  If that's the correct data rate, then you might have a shot--at least rate-wise.  On the other hand, if the data communication standard is similar to HDMI, where each clock contains 10 bits, then ... there's no chance there.

In my simple quick look, I couldn't find the list of wires.  The Arty only has 4-pairs of wires which can be used as differential signals.

Looking back at the spec again, it looks like the device is designed for a 0.6V LVDS standard.  The Arty's PMod will only support a 3.3V output.  Hence, without a voltage translator, you probably aren't going to make it.

Dan

[jpeyron]

Hi @glenalec,

Unfortunately the Pmod ports only support 3v3 and would only be able to support TMDS_33 and not LVDS 2.5V as discussed here. Pmod ports JB and JC are deferentially paired and are considered high speed ports. Here is another thread that deals with the Pmod ports frequency capabilities. I would also like to suggest the Nexys Video which has a LPC FMC that has  34 differential pairs that can have their voltage adjusted to 1.2V, 1.8V, 2.5V and 3.3V.

cheers,

Jon

[glenalec]

A TDMS to LDVI bridge is an acceptable solution for me if that is any help.

(It puts us back in HDMI-territory again, but my main interest here is the possibility of getting a panel running off the Artix-7 board)

I am beginning to think an Arty Z-7 board might suit me fine. While I don't need a lot of the functions of the Arm-7 CPU, I can always ignore them (even forbid them in the compiler to make sure I am cross-compatible if I change cpus).

FYI - I am ideally wanting a CPU that lacks floating-point, but instead has strong 32-bit fixed-point (s15.16 format) and 16-bit normals (which I envision as just adding a saturate function to the fixed-point-unit and load-store from the bottom 16-bits of the register). I'm sure I can emulate this functionality on an ARM core with the FPU deactivated, but being more from a hardware background in my dim past, I am leaning towards the idea of learning how to make my own simple CPU that does just what I want. The system is intended to provide fixed-point 3D graphics and needs a screen to output on, hence this bit of my query. (Despite the graphical focus, speed isn't a primary concern at present, so FPGA is fine for learning on - if I can get performance comparable to a Commodore Amiga 500 I am happy :-)  ).

[D@n]

@glenalec,

When you state that you are "wanting a CPU" ... does that mean you are looking for one, or intending to write one?

Can I offer you a ZipCPU?  It is completely open source and it can run just fine on the Arty ...

Dan

[glenalec]

Looking at designing my own, though it has very specific requirements. Examples are always welcome, however

(I have never done a FPGA before, but I have a reasonably solid, if dated, knowledge of how logic gates and more complex systems work. I'm confident I could design something on the scale of a 6502, but obviously more advanced stuff like pipelining, caches, etc. are going to be beyond me!)