Why VGA and not DVI/HDMI


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lew247

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Joined: 23/12/2015
Location: United Kingdom
Posts: 1584
Posted: 10:49am 30 Jan 2022      

  Mixtel90 said  A:  The chip on the QSPI is flash RAM, not fast access RAM. It's much slower to access and has a shorter lifetime.


QSPI has XIP
"XIP stands for eXecute In Place, it is a feature which allows the microcontroller to execute code straight from the external flash memory without copying it first. This allows for faster and more efficient execution of code"

  Mixtel90 said  
B: The Raspberry Pi Pico only has 2MB of flash RAM on the QSPI. Yes, the RP2040 can address 16MB but only if it's got it. :)


W25Q128JVSIQ-ND 16Mb thousands in stock Digikey simple swap chips to use

  Mixtel90 said  
The Pico can only output 720P video *at all* if it's not doing anything else. You couldn't do that and run MMBasic on the same Pico at the same time. There isn't enough RAM.
 
XIP?

  matherp said  1080p
1920*1080 = 2073600 /8 = 259200 bytes = 253Kb
Total memory on RP2040 is 264kB
This has been explained above.  These demos are just that and have no useful significance for MMbasic


1080P was black and white only -no use in real life

720P was full colour and according to your calculations would be
1280*720 = 921600 /8 = 115200 bytes = 112.5Kb

As the QSPI interface used on the Pico is not only fast but it also has XIP can this not be used as a frame buffer?

  Grogster said  As I note that the Pico module use QSPI for the external memory device, I decided to read a little more about it - it is a clever interface.

QSPI description

This page is easy to understand despite QSPI being quite complicated in and of itself.

I found this a very interesting read.