QL Pico VGA

[Derek_Stewart]

I will maybe get a batch of 30, which would include the Pico RP2040-Zero

Please keep in mind it is currently required to desolder the LED from the module. Not a nice job for 30 pieces.

Okay will think about it, got the next batch of Q68 underway at present.

[Oliver]

.. Maybe Oliver will provide alternative IO for regular module pins later...

Hi all, greetings, I have started a development branch for the PR2040-Zero: https://github.com/holmatic/video_if_ql ... i_pico_vga

Here is the first test build:

video_if_ql_vga_minipico002.zip

(26.95 KiB) Downloaded 280 times

New: Hsync and Vsync outputs are duplicated to accomodate for the shrinked layout:

Code: Select all

 GP16-out = GP12-out = VGA-HSYNC

 GP17-out = GP14-out = VGA-VSYNC

Please note that I have just checked the replicated outputs with an Oscilloscope, not on the real board (still on it's way..)


Update:

video_if_ql_vga_minipico002b.zip

(26.93 KiB) Downloaded 293 times

Variant B with only GP12/14 as sync, after reports of artifacts in the sync-duplication variant above.

Code: Select all

GP12-out = VGA-HSYNC

GP14-out = VGA-VSYNC

[bwinkel67]

Since the composite video pin in my QLs is unconnected, I use it for the 5V supply. The converter needs less than 20 mA and a little electronic fuse can be used for protection, in the extremely unlikely case a QL device uses that signal (I have never seen any).

Are you talking abut pin 1? Did you disconnect that on your QL? On the US QLs it doesn't output a composite signal but instead gives 5 volts. Never understood why.

[bwinkel67]

Also note that I did not add a cable relief in order to keep size as small as possible. So that needs to be covered by the HD-Sub case.

How does your prototype connect to a monitor being so short? Are you using a male or female DB-15 connector? I had looked to make one using the Pico, and was thinking of using a female DB-15 connector with a short cable, so I could then connect it to a normal VGA cable. I feared that some monitors have their VGA connector in a weird place (i.e. pointing down -- most of mind are awkwardly like that) and anything other than a standard VGA cable might be a bit hard to fit in to connect.

I thought it would be a nice compact design and then you create this awesome miniature version...makes me now want to wait to see if Derek makes a few Of course it also depends on how the 5 volts is fed in since on my QL, pin 1 is already set for that.

Edit: you never actually see the connector on the github page and for whatever reason I thought it was male...but looking at it more closely I think it's actually female, so never mind...[slaps forehead]

[Peter]

Are you talking abut pin 1? Did you disconnect that on your QL?

No, about Pin 3.

On the US QLs it doesn't output a composite signal but instead gives 5 volts. Never understood why.

If you have a dedicated 5V pin, you're even better off.

[Peter]

How does your prototype connect to a monitor being so short? Are you using a male or female DB-15 connector?

I used a female HD-Sub, so I can use the normal VGA lead.

I thought it would be a nice compact design and then you create this awesome miniature version...makes me now want to wait to see if Derek makes a few

With the latest update from Oliver, maybe you can even build it yourself.

Edit: you never actually see the connector on the github page and for whatever reason I thought it was male...but looking at it more closely I think it's actually female, so never mind...[slaps forehead]

Slapping my own forehead, as I replied without reading all of your post first.

[Derek_Stewart]

Hi

Due the change of the HSYNC & VSYNC to GP12 & GP14, require changes to the schematic and layout?

With regards to using QL Pin 1 (Composite PAL) for 5V power, I do not want alter the QL, so it maybe safer to use the Micro USB connector to power the Pico-Zero and VGA adapter.

Some modern LCD monitors have USB connections, so the adaptr can be powered that way.

I would fit a 90 Degree pin header to the RGB connector and not solder to the board.

One question about the LED attached to GP17, since this is not used, can the LED be used as an indicator?

[Peter]

Due the change of the HSYNC & VSYNC to GP12 & GP14, require changes to the schematic and layout?

Not really, I just updated the comments in the schematics, attached.
If you read even the old schematics and look at the pictures, you see that the PCB only connects to pins 1 to 10 of the HD-Sub!
Consequently, HSYNC & VSYNC must be directly wired from the RP2040-Zero module to Pins 13 and 14 of the HD-Sub.
The recent change just makes that easier, so you have decent throughhole pads to connect, and do not need to desolder the LED.

Think of this: A HD-Sub has three rows of pins / solder buckets! How would you directly connect a PCB to that, if you want to fit a D-Sub case?

The new wiring on the bottom side looks like this:

[Peter]

Some modern LCD monitors have USB connections, so the adaptr can be powered that way.

If you want to power it from the monitor side, the board also allows to use VGA pin 9 for that.
Some VGA wirings have 5V on that pin, but use with caution, as they usually come from the graphics card, not the monitor.
For this option you can solder a 0805 size fuse (or 0 Ohms resistor for the brave) on the board.

Maybe you could make a special Y - VGA cable for the monitor end, which leads to both its VGA input and the USB connector.

[Derek_Stewart]

Hi Peter,

Your earlier photographs show the Mini VGA board soldered to VGA pins 1-5, whivh should support the VGA and Pico RP2040-Zero.

A wire link from GND to VGA pins 6,7,8 and wite links to HYSNC, VSYNC. Pity VGA pin 5 was not connected to GND, so that a common connection to 5,6,7,8, would save wire link.

I thought the converter could be fitted into this type of D-Sub case:

D-Sub shell

The adapter could be powered by the RP2040-Zero USB connector from the monitor or other USB Power supply.