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Author Topic: BT815 in HD  (Read 3796 times)

FlorianG

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BT815 in HD
« on: July 23, 2019, 03:43:52 PM »

Hi everybody.

I saw on a PDF available on the site of Bridgetek that there was possibility to make HD (1280 * 800) with the BT815.
https://brtchip.com/Brochures/BT815_6%20Demosheet.pdf
The problem is that he asks to contact them but I have not yet had an answer. So I do not know how that's possible.

Someone could help me on the subject ?
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Re: BT815 in HD
« Reply #1 on: July 24, 2019, 11:39:54 AM »

Hello,

Sorry, what is your question? Are you looking for the HD Demo source or?

Best Regards,
BRT Community
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FlorianG

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Re: BT815 in HD
« Reply #2 on: July 24, 2019, 02:38:09 PM »

Thank you for your reply.

I'm trying to know how it works
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Re: BT815 in HD
« Reply #3 on: July 24, 2019, 04:04:55 PM »

Hello,

Sorry again, you're being very ambiguous, I assume you mean how the HD demo is coded and not 'how EVE works'?

Thank you for your reply.

I'm trying to know how it works

Best Regards,
BRT Community
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FlorianG

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Re: BT815 in HD
« Reply #4 on: July 24, 2019, 06:37:47 PM »

Hello,

Ho there is no hardware modification to do? There is only the LVDS addapator ?
Yes I want to see the code please.
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FlorianG

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Re: BT815 in HD
« Reply #5 on: July 25, 2019, 09:19:41 PM »

And I have another question. If the BT815 is capable of handling 1280 * 800 with an LVDS adapter.
Is it able to manage a 1024 * 600 screen without an adapter?

This one for example:
http://www.hotmcu.com/7-inch-1024x600-tft-lcd-display-with-capacitive-touch-panel-p-70.html?cPath=6_16
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Re: BT815 in HD
« Reply #6 on: July 26, 2019, 11:35:07 AM »

Hello,

The use of an LVDS adapter turns out isn't relevant to your question, it just happened that the demo used an LCD panel with an LVDS interface and not an RGB interface.

The EVE series of ICs do not include a frame buffer, they dynamically clock out each computed pixel on the screen. A displays size and what the Pixel Clock is running at will determine the achievable performance. It is possible to run the BT81x at higher resolutions, but this will result in a slower refresh rate for the screen.

If we take a working example from the following WQVGA settings:
 
Code: [Select]
// WQVGA display parameters
   lcdWidth   = 800;                                                            // Active width of LCD display
   lcdHeight  = 480;                                                            // Active height of LCD display
   lcdHcycle  = 928;                                                            // Total number of clocks per line
   lcdHoffset = 88;                                                             // Start of active line
   lcdHsync0  = 0;                                                               // Start of horizontal sync pulse
   lcdHsync1  = 48;                                                            // End of horizontal sync pulse
   lcdVcycle  = 525;                                                           // Total number of lines per screen
   lcdVoffset = 32;                                                            // Start of active screen
   lcdVsync0  = 0;                                                              // Start of vertical sync pulse
   lcdVsync1  = 3;                                                              // End of vertical sync pulse
   lcdPclk    = 2;                                                                  // Pixel Clock
   lcdSwizzle = 0;                                                              // Define RGB output pins
   lcdPclkpol = 1;                                                              // Define active edge of PCLK                 

HCYCLE = 928
VCYCLE = 525
VCYCLE * HCYCLE  = 487,200

Note: REG_PCLK is using the value 2 which will divide the clock down to 30Mhz (assuming system clock of 60Mhz).

Result = 30,000,000/487,200 = ~ 61 fps


Best Regards,
BRT Community
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FlorianG

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Re: BT815 in HD
« Reply #7 on: July 27, 2019, 02:11:01 PM »

Thank you for your reply.

OK so if I understand well. If I put the screen that I shared with you just before it will be possible to pair it with the BT815 with 40pin RGB connector and set parameters :

   lcdWidth   = 1024;                                                            // Active width of LCD display
   lcdHeight  = 600;                                                            // Active height of LCD display
   lcdHcycle  = 1114;                                                            // Total number of clocks per line
   lcdHoffset = 90;                                                             // Start of active line
   lcdHsync0  = 0;                                                               // Start of horizontal sync pulse
   lcdHsync1  = 48;                                                            // End of horizontal sync pulse
   lcdVcycle  = 610;                                                           // Total number of lines per screen
   lcdVoffset = 10;                                                            // Start of active screen
   lcdVsync0  = 0;                                                              // Start of vertical sync pulse
   lcdVsync1  = 3;                                                              // End of vertical sync pulse
   lcdPclk    = 1;                                                                  // Pixel Clock
   lcdSwizzle = 0;                                                              // Define RGB output pins
   lcdPclkpol = 1;                                                              // Define active edge of PCLK

HCYCLE = 1114
VCYCLE = 610
VCYCLE * HCYCLE  = 679,540

Result = 30,000,000/679,540 = ~ 88 fps

Yes I am also looking to exceed 60 fps
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FlorianG

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Re: BT815 in HD
« Reply #8 on: July 28, 2019, 10:52:10 PM »

*Result = 60,000,000/679,540 = ~ 88 fps
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Re: BT815 in HD
« Reply #9 on: July 29, 2019, 09:47:58 AM »

Hello

Please see table 4.11 in the BT81X datasheet (page 27), it is not possible to run the PCLK at the same rate as the system Clock (60Mhz in your calculation), the highest achievable would be 36Mhz:
https://brtchip.com/wp-content/uploads/Support/Documentation/Datasheets/ICs/EVE/DS_BT81X.pdf

This would give you an approximate FPS of (36,000,000/679,540) = ~ 53.

I would however advise that running the PCLK at the fastest possible rate reduces the computation time available for each pixel on the screen. This can cause issues if the GPU runs out of time to calculate what it should display for a given pixel if many graphics elements intersect this given point. In simple terms the faster you run the PCLK the less complex of a Display List you can run on the screen.

Best Regards,
BRT Community
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FlorianG

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Re: BT815 in HD
« Reply #10 on: July 29, 2019, 11:30:55 AM »

So if I understand correctly the maximum PCLK speed available for the BT815 (36Mhz) is lower than that of the ft81x (60Mhz) .

So for what reason it is said that it is possible to make HD with the bt815 on the PDF available on your web site? How is it possible ?
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Re: BT815 in HD
« Reply #11 on: July 31, 2019, 10:07:09 AM »

Hello,

No, if you read the datasheet for the FT81X you will see that the max PCLK available is 30MHz (hence using this number in the above calculations).

The term HD in this context refers to the screen resolution, not necessarily the screens frame rate (which the document does not reference). It is possible to run EVE at these higher resolutions, though this will incur a performance penalty in terms of frame rate. EVE is designed primarily to be an HMI, and is optimized to give a good visual experience for such use cases, it is not designed to be for example to be a high frame rate video player, although it can be used to display video. I would suggest the differences between 60 and 53 fps in this scenario is negligible.

Best Regards,
BRT Community
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FlorianG

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Re: BT815 in HD
« Reply #12 on: August 08, 2019, 10:23:02 AM »

Hello,

sorry but that's not what I saw on the ft81x Datasheet on page 26


More than 60 Mhz works correctly on my FT81x .
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Re: BT815 in HD
« Reply #13 on: August 08, 2019, 01:18:33 PM »

Hello,

It is not recommended to run REG_PCLK = 1, this will significantly short the computation time for each pixel.
Theoretically it is possible, but the likelihood of you running into issues when adding components on the screen and the GPU not having enough computational time to calculate for a given pixel is high. So yes, you can run the PCLK at 60MHz (if your chosen LCD supports this), but I suggest once you actually start developing your application you will need to lower this.

Again, EVE is designed primarily to be an HMI, and is optimized to give a good visual experience for such use cases, it is not designed to be for example to be a high frame rate video player or similar.

Best Regards,
BRT Community
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FlorianG

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Re: BT815 in HD
« Reply #14 on: August 08, 2019, 08:23:24 PM »

Hello and thank you for your answer,

ctually I am well aware that the calculation time is greatly reduced. I plan to reduce the REG_PCLK by two if the run program needs a lot of items to display simutanerment and not display speed.

(Depending on the program run, I know it is not possible to change it instantly. Well I think).

But I'm not ready to finish my project and I'm moving to the BT815. Does it support the REG_PCLK = 1? If this is not the case are that another graphics chip is planned?

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