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Author Topic: FT82x  (Read 3587 times)

armadafg

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Re: FT82x
« Reply #30 on: October 30, 2018, 09:29:25 AM »

Anyway, even if there were only 256m it would still 256 times more than the ft81x
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armadafg

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Re: FT82x
« Reply #31 on: October 30, 2018, 03:16:30 PM »

I would like to know if it is possible to exceed 60 i / ps with the FT81x or bt81x?
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Re: FT82x
« Reply #32 on: October 31, 2018, 10:37:16 AM »

Hello

Basically the refresh rate depends on which Display you are using, the PCLK that this display can support, and its size. Multiplying the HCYCLE and VCYCLE values will give you the total number of Pixels to be rendered, dividing this number by PCLK will give you the theoretical refresh rate for the display.

Best Regards,
FTDI Community
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armadafg

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Re: FT82x
« Reply #33 on: October 31, 2018, 11:36:03 AM »

thank you for your reply.

So if I understood well with this screen : http://www.haoyuelectronics.com/Attachment/HY5-LCD-HD/KD50G21-40NT-A1.pdf
I do 1 / ((800 * 480) / 50000000).
which makes 130 i / ps ?
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Re: FT82x
« Reply #34 on: October 31, 2018, 01:30:11 PM »

Hello,

If we take the 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.

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

The intention in this example is to get the refresh rate at or near 60 fps, but if your display can support higher PCLKs then a higher refresh rate should be possible.

Best Regards,
FTDI Community
« Last Edit: October 31, 2018, 01:31:48 PM by FTDI Community »
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armadafg

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Re: FT82x
« Reply #35 on: October 31, 2018, 02:11:59 PM »

ok i understand better.
For this screen in question the frequnce max is 50mhz, so the best conbinaison with the ft811 or bt81x is 30Mhz ?
And for the bt81x it is necessary to find a screen with 72mhz max to use all this capacity? That's right ?
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Re: FT82x
« Reply #36 on: October 31, 2018, 03:30:10 PM »

Hello,

In general most displays target around a 60 fps refresh rate, as such settings are chosen to achieve this. In the previous example the clock was divide down to 30Mhz as this number combined with the HCYCLE and VCYCLE values got use very close to this desired number (60). It is normal practice to divide PCLK by 2 or more to achieve the desired frequency which best fits the display being used.
It is not the intended use of EVE to run at 'full tilt' with a display that can match the overall system clock of the IC.

Best Regards,
FTDI Community
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