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Thread: 256k sram

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    Default 256k sram

    Hello,

    I am working with TFT and AVR. Since graphic app requires lot of SRAM, I am thinking of ATmega128 + 256K external SRAM. Approx 150KB will be used to double buffer the main graphic for flicker free movements. The rest will be used to keep app related graphics. My design is almost final, I just need the chip http://www.issi.com/pdf/61LV2568L.pdf(IS61LV2568L-8TL). If any one know some good dealer where I can find the chip, please help.

    I know that AVRs support at most 64K ram but from software control of address lines A16 and A17 we can use more memory.

    The Idea is that the graphic library I will develop do all rendering to the second buffer that is on SRAM (not directly to the screen) this way the final output can be finally sent to any graphic hardware like TFT or TV or VGA by developing suitable low level drivers.
    Avinash Gupta
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    www.eXtremeElectronics.co.in

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    Administrator T-1000 vikas's Avatar
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    Nope no vendors i know of in india who supply it.

    Some points if you are looking at developing a smart/serial TFT ( as they are called )

    8 bits are simply too underpowered to driver TFT's
    12 to 32 bit with PMP and DMA are the microcontrollers you should be looking for.
    PIC24F is a nice start ( Awesome microchip graphics library you get for free )

    Look into PIC24FJ256DA210 if possible.

    You can also go for STM32 ( 72 Mhz ) / LPC1768 ( 1000 Mhz ) and eliminate the external ram ... these are very powerfull and handle TFT with ease ... though at a little higher component cost.
    Vikas Patial

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    My AIM was to create a system that can drive a TFT in most simplest manner, thus most easy for new developers. Going 16bit or 32bit adds complexity. I don't need very high performance. As we know AVR are most common MCUs worldwide by hackers and hobbyiest so I just wanna develop a library for it.

    For commercial perpose we can go for 32 bit.

    The problem is that Chinese are having their new year (which is the biggest festival of China) other wise my loyal friends their could have already found it for me.

    Looks like I have ta wait till 10th Feb

    I though a ATmega128 board with SRAM and TFT would be a nice thing. Portable Graphic lib can then be ported to PICs and ARM etc too.
    Last edited by avinash_g; 02-01-2011 at 01:36 PM.
    Avinash Gupta
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    www.eXtremeElectronics.co.in

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    I understand what you are trying to devlop , i was also trying to do the same thing 2 months back , but little stuck with some other product launch.

    What its called is a smart lcd , 4d systems is the current market leader

    http://www.rhydolabz.com/index.php?m...b39efb37877b7e

    The user finally gets a high speed SPI / serial interface ... he does not bother with whats inside.

    Initially i too planned on coding a library too, but after looking at Microchips i dropped the idea ... huge library with good driver support and free. Also commercial libraries like from RAMTEX offer so much more ...
    Vikas Patial

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    Quote Originally Posted by avinash_g View Post
    My AIM was to create a system that can drive a TFT in most simplest manner, thus most easy for new developers. Going 16bit or 32bit adds complexity.
    Albert Einstein: "It can scarcely be denied that the supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience". More conveniently written as: Make things simple, but not simpler.

    Point is, don't overdo the simplification. 16-bit microcontrollers are, in fact, simpler to use than 8-bit. The instruction set is better (if you code in assembly). There are more features, hardware and peripheral wise. They are faster. Have more memory.

    I mean, an Atmega with external SRAM cannot be simpler than a 16-bit PIC with more memory and DMA.


    I don't need very high performance.
    With a TFT, I think you do. :-)


    As we know AVR are most common MCUs worldwide by hackers and hobbyiest
    Another time, another place, I might have debated this; but what's the point... Neither can you prove your quote nor can I disprove it. :-)
    --
    Mohit Mahajan,
    www.BioZen.co.in

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    @MohitM

    If I was designing the library for me or your or Vikas, then I might have used 32bit. But I am creating this for those who don't know what is a CONFIG word in PIC16 or FUSE byte in AVRs. If only we jump from PIC16 to PIC18's we have complicated CONFIG Words that too 14 of them. We need to patiently read the clock source structure and complex PLL configuration just to get the CPU breathing.

    Simplicity is most important that they are very overdone in most successfull products.

    Why we have USB? (Earlier we have to configure port address and ISRs manually and ISA devices broke badly and adding hardware was nightmare)
    Why we have PnS camera if DSLRs are there? (Coz in some case a buggy program running on CPU is considered wiser than a human brain! 3 cheers for AUTO mode!)
    (I have to wait 4 days to get a high end camera coz most retailers were selling common peoples cameras )
    Why Windows rules desktop if Linux is there?
    Why GUI won the battle?
    Why we have autoplay?
    Why people buy a Rs 1500 water purifier more than a Rs 8000 aquaguard.
    Why people sit on top of train roof first and then burn the train?
    Why we have suncream in India?

    You are following RI regularly and know people don't go no further than a line follower! And the type of querries asked.
    And most Videos posted by Vikas are from some other planet.

    Many people asked me that the programmer is not opening the .C file I just wrote! Hey man forgot the compiler?

    I have the experience of running Microchip Application library (USB part) but to get them running on a particular configuration we need to do lot of setting, as the same code if wriiten to support 8,16 and 32 bit MCU. There were lots of conditional compilation and pre-processor magic going inside. After editing the linker script and lots other tweek I got it working!

    If you look at Mobile OS's
    Symbian ^3 is simpler UI than S60v5 which was simpler than earlier S60 devices.

    Even when I saw Android it was much less geeky (bigger font size, over smart software).

    Theoretically we can write program in ANY text editor and compile using command line tools. But the Worlds(even me) uses high end IDEs with syntax highlighting and code completing (the basic use of computer or any machine is to free humans from work as much as possible), Now even open source developers use Netbeans and other IDEs which offer such service for free (but MS where first to create a flawless syntax highlight and code completion features).
    Last edited by avinash_g; 02-02-2011 at 09:51 AM.
    Avinash Gupta
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    www.eXtremeElectronics.co.in

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    I am working with TFT and AVR. Since graphic app requires lot of SRAM, I am thinking of ATmega128 + 256K external SRAM. Approx 150KB will be used to double buffer the main graphic for flicker free movements. The rest will be used to keep app related graphics. My design is almost final, I just need the chip http://www.issi.com/pdf/61LV2568L.pdf(IS61LV2568L-8TL). If any one know some good dealer where I can find the chip, please help.
    No idea, the link does not work.

    If I was designing the library for me or your or Vikas, then I might have used 32bit. But I am creating this for those who don't know what is a CONFIG word in PIC16 or FUSE byte in AVRs. If only we jump from PIC16 to PIC18's we have complicated CONFIG Words that too 14 of them. We need to patiently read the clock source structure and complex PLL configuration just to get the CPU breathing.
    Never. Never make something like this for people who dont know about fuse bits. In my opinion, they wont be able to write an SPI code themselves. You CANNOT do much more than static displays with an 8 bit micro and a TFT. I guess you know about it.
    If you have worked with TFTs(or any displays), you know the limitation of driving them with a low frequency/ 8 bit processor.


    And most Videos posted by Vikas are from some other planet.
    That was an avoidable statement. Not at all related to the SRAM we were discussing about. These things happen in our planet, we see them a lot, in videos and in real, and if you think they are from a different planet, you need to seriously update your robotics point of view. All of the 8 videos posted by you are demos, mostly for advertisement sake, providing people with no knowledge at all. They do not motivate or give information about any technology. Please stick to the topic. I have refrained from saying this for long, but i do see a lot of arrogance in most of your posts.

    You are following RI regularly and know people don't go no further than a line follower!
    If you believe this, you should not build your display project, because no one is going further than the line follower. So, they simply will not use your display driver.


    I have the experience of running Microchip Application library (USB part) but to get them running on a particular configuration we need to do lot of setting, as the same code if wriiten to support 8,16 and 32 bit MCU. There were lots of conditional compilation and pre-processor magic going inside. After editing the linker script and lots other tweek I got it working!
    It is going to be the same, for your library too. or else, your library will be specific to one chip or one board, probably manufactured by you.
    .... I didnt do it ! ....

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    Sticking back to topic -

    I always assume people are lazy , they will do minimum work required. But as a product developer designer you have to overcome this.

    For TFT's a serial driven TFT is the simplest way to drive one , lot of examples around. To the end user he simply gets a serial port connection on a tft board thats all , nothing can be easier than issuing command in serial or connecting a serial tft ( just 3 wires ). The example i provided is of a serial TFT ( though at 5k they are expensive ).

    A 89c2051 can drive a serial TFT , so can you Quad core PC and it is architecture independent. So it is the best bet for most beginners in TFT.

    Now lets talk of the smart panel which i proposed -

    To drive a tft decently you need atleast a 16 bit bus and some other io and a powerful micro controller . Though you can drive with SPI , results are not satisfactory. It is recommend to use a use a chip with PMP and DMA. Also most smart tft controllers will come with sd slot , graphics/video/audio can be stored in a cheap card making final output look and sound great great. Also SDcards in SDIO Mode with DMA are really awesome.

    Do go through the documents of the link i provided , you will see it is damn simple to use and connect ... but as its expensive due to proprietary controller and software the final result is expensive. A serial TFT under say Rs 1000 will be awesome and Rs 2000 will be great .

    But if you just wish to build a library then the above will not be relevant to you , In that case some observations -
    Preferably write a generic library ( like HAMTEX one )
    Wiring 40 lines to a uC from a LCD is not easy , even one error can cause the thing to not work.
    Also TFTs require care , Recently I tore the plastic ribbon connector when connecting a 7" to a controller ... i was like WTF.
    Also if you look the numbers of TFT controllers out there with no documentation it is insane

    I would recommend build a smart panel inspired from 4d systems , and i will be your first buyer .
    Vikas Patial

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