6502 with the RA8875

[AndrewP]

Speaking of lens separation, this is the setup I'm using:

Which gives plenty of room for soldering. The microscope is just cable tied to a desktop microphone stand; as are a couple of flexibe LED lights.

Right! back to the RA8875

[AndrewP]

GlennSmith wrote:

PaulaM wrote:

What size screen is that? 7"?
I recently got a 9" RA8875 from BuyDisplay and it doesn't work

Yes, it's a 7" display. I had to rewire all of the jumpers to get it to work in 6800 // mode, it was hard-wired for 8080 mode. I followed the diagram to the letter, and presto! the beast came alive.

RA8875_8-bit_6800.png

(EDIT: Thanks for the A'zon link.)

Just quoting Glenn's last message as I've knocked it off the page.

[PaulaM]

I got my 9" RA8875 working, Here is a Mandelbrot at 800x480, 16 itterations, 8 bit colour depth and custom colour scheme.

The display still has it's screen protector on, it's also really difficult to photograph.
I'm not 100% the panel itself is great, it's ok, but viewing angle isn't great for this type of thing so I may try and get the IPS TFT I have working (using a different controller chip)

But I am happy, and oh, this took about 3 hours to render at 8MHz

[GlennSmith]

Cool pic!
Two last questions (I hope) :

• I'm trying to read back from TEXT memory - has anyone managed to do this? (ie I would like to be able to make a sort of screen-based editor)

So far I'm always getting zeros wherever I place the read cursor...

• I have a resistive touch panel, which worked fine, but which now doesn't respond - anyone experienced similar problems?

I don't think I've ever had to spend so long getting a finished product to work properly!

[kakemoms]

GlennSmith wrote:

Are there any microscopes out there in china.com land that are worth the money? As a hobbyist, I mean.

One of my friends has an Eakins Zoom 3.5X-90X Trinocular which he is very happy with. You can find it on aliexpress.

[PaulaM]

GlennSmith wrote:

Cool pic!
Two last questions (I hope) :

• I'm trying to read back from TEXT memory - has anyone managed to do this? (ie I would like to be able to make a sort of screen-based editor)

So far I'm always getting zeros wherever I place the read cursor...

• I have a resistive touch panel, which worked fine, but which now doesn't respond - anyone experienced similar problems?

I don't think I've ever had to spend so long getting a finished product to work properly!

No something I've tried, sorry.

I'm currently wrangling with the BTE engine trying to copy a portion of the screen to another (so I can do scrolling text when you do "LIST") but I'm losing the will to live rapidly.

[AlexeyM82]

Good day, friends.
I managed to connect an 8-inch display to my 6502 via SPI and display text, change colors, and clear and fill the screen. I was also able to activate the text cursor and graphic cursor, activate the touchpad, and position the cursor when tapping. I have a question: with an SPI bus frequency of 6 MHz and a processor frequency of 4 MHz, the time to completely fill the screen using the processor (not using the PA8875) is about 8.5 seconds. That's slow. How fast does this happen with a parallel connection? Theoretically, it should be 8 times faster, about 1 second. Can you tell me? I haven't tried a parallel connection yet.
Below is a photo of the prototype SPI I2C interface board and a working display.
links to videos of the screen filling and the touchpad and graphic cursor in operation. https://drive.google.com/drive/folders/ ... sp=sharing
And one more question: is it correct to hang a 5V - 3.5V level converter chip directly on the data bus without an intermediate buffer?

[GlennSmith]

Hello, I'm not sure I completely understand the questions you ask, but any operations that involve filling or moving screen data should be left to the graphics processor : the RA8875. A complete fill of the 8" (800x480 pixels) screen takes much less than 1s. You need to watch the !wait signal to pace the commands, but the speed is completely independent of the SPI or // interface speed.
As for the level translators, you can place them directly on the bus(es), but you'll need to place them in a high-impedance state when not in use.

[PaulaM]

Hi Alexey,

As Glenn says there is a way to clear the screen quickly, use the built in engine to draw a square that is the size of the screen, in black and then fill the square in black.
It needs about 16 commands, to be sent, but takes a fraction of a second (I think I measured around 270milliseconds to do this).

with reference to the level translators I used the TX0108, and as Glenn says again, when I'm not reading/writing to the display it is in the high impedance state.

[AlexeyM82]

GlennSmith wrote:

Hello, I'm not sure I completely understand the questions you ask, but any operations that involve filling or moving screen data should be left to the graphics processor : the RA8875. A complete fill of the 8" (800x480 pixels) screen takes much less than 1s. You need to watch the !wait signal to pace the commands, but the speed is completely independent of the SPI or // interface speed.
As for the level translators, you can place them directly on the bus(es), but you'll need to place them in a high-impedance state when not in use.

Dear friend, thank you very much.
I understand about the converters.
Regarding the screen fill rate with the 6502 (when the processor writes directly to graphics memory), I'll explain why I conducted this evaluation. I'm trying to assess how comfortable it would be to work with this screen, for example, when creating games. For example, displaying a bit-perfect 800x480 image (for example, a game board) from RAM or disk. A simple fill task was used as a primitive example. If you saw in the video, in my case, it takes about 8.5 seconds using the SPI. So I wanted to know how fast it works when using a parallel interface.
I hope I've conveyed the essence of the question.

[PaulaM]

I managed to get scrolling working on my 6502 laptop screen.
This uses the block transfer engine, which copies the bottom portion of the screen (0,16 - 800,480) to the top of the screen (0,0) and then fills the bottom 16 pixels with black (draw fille square in black).
The scrolling is instant and seamless

https://files.mastodon.social/media_att ... 8741af.mp4

[AlexeyM82]

PaulaM wrote:

I managed to get scrolling working on my 6502 laptop screen.
This uses the block transfer engine, which copies the bottom portion of the screen (0,16 - 800,480) to the top of the screen (0,0) and then fills the bottom 16 pixels with black (draw fille square in black).
The scrolling is instant and seamless

https://files.mastodon.social/media_att ... 8741af.mp4

Hello, Paula!
As far as I understand, this scrolling task was purely for testing the BTE's capabilities? As far as I remember from the datasheet, the RA7588 has powerful screen or window scrolling capabilities, both horizontally and vertically.

[AlexeyM82]

PaulaM wrote:

Hi Alexey,

As Glenn says there is a way to clear the screen quickly, use the built in engine to draw a square that is the size of the screen, in black and then fill the square in black.
It needs about 16 commands, to be sent, but takes a fraction of a second (I think I measured around 270milliseconds to do this).

with reference to the level translators I used the TX0108, and as Glenn says again, when I'm not reading/writing to the display it is in the high impedance state.

Paula, I looked at your circuit from the posts above. In it, the OE converter inputs are connected to the +3.3 volt circuit. Could you please tell me how they are configured for high impedance operation? Or is there a modified circuit? What signal controls the OE?

[PaulaM]

AlexeyM82 wrote:

PaulaM wrote:

I managed to get scrolling working on my 6502 laptop screen.
This uses the block transfer engine, which copies the bottom portion of the screen (0,16 - 800,480) to the top of the screen (0,0) and then fills the bottom 16 pixels with black (draw fille square in black).
The scrolling is instant and seamless

https://files.mastodon.social/media_att ... 8741af.mp4

Hello, Paula!
As far as I understand, this scrolling task was purely for testing the BTE's capabilities? As far as I remember from the datasheet, the RA7588 has powerful screen or window scrolling capabilities, both horizontally and vertically.

Not quite, the built in scrolling "wraps" the window, so whatever goes off the bottom appears at the top. This means that the origin (x = 0, y = 0) moves as the screen scrolls.

[PaulaM]

AlexeyM82 wrote:

PaulaM wrote:

Hi Alexey,

As Glenn says there is a way to clear the screen quickly, use the built in engine to draw a square that is the size of the screen, in black and then fill the square in black.
It needs about 16 commands, to be sent, but takes a fraction of a second (I think I measured around 270milliseconds to do this).

with reference to the level translators I used the TX0108, and as Glenn says again, when I'm not reading/writing to the display it is in the high impedance state.

Paula, I looked at your circuit from the posts above. In it, the OE converter inputs are connected to the +3.3 volt circuit. Could you please tell me how they are configured for high impedance operation? Or is there a modified circuit? What signal controls the OE?

for the status/control lines (RnW, nCS, E, etc) they are connected to a CPLD.
For the databus There is an enable like, through a resistor diver that is controlled by the CPLD (this is actually the same as the chip select, just inverted so it is active high)