TFT with RX62N dev board

Hi all,

I am willing to make a TFT example by the use of this board here: http://www.renesas.com/products/tools/introductory_evaluation_tools/renesas_demo_kits/yrdkrx62n/

I know I can do it with other micros but I intend to learn Renesas controllers and this will be  a final project.

I am willing to build a car dashboard and control system (a proof-of-concept one), but I can not afford paying too much.

I saw the direct drive LCD board costs a lot (about 550$)... I can only pay around 100$ which is why I picked this dev board. Can I use "direct drive LCD" with this board? if not, then what driver I must use? give me some examples plz. how about the RTOS? I also need free software/

thanks,

Hossam 

  • Hi Hossam,

    The YRDKRX62N board is not suitable for direct drive TFT LCD. The RX62N package version on that board does not have sufficient available I/O pins for the TFT interface. It is a 100 pin package and most of the pins are already committed to other functions on the board. Also, the DDLCD application requires external SDRAM that is not available on that board. The 100 pin package RX62N device does not have the SDRAM controller or EXDMA controller that is used by the DDLCD application. 

  • In reply to Gerald:

    Hi Gerald,

    Well, you wrote some good info. However, what do you suggest in this? as I told you, paying 550$ for one board is just too much, and I can not do it really.

    How about using the 100$ board with external driver chip and external SRAM? can it be done? can you name the renesas devices that has DDLCD and DMA?

    Also, does the pricey board has programmer/debugger that can actually be used with renesas chips themselves without the board (like PICKit3 for PIC)?

    thanks

  • In reply to VEGETA:

    How about the Embedded GUI Solution Kit?

    YLCDRX63N am.renesas.com/.../index.jsp

    It sells for about $200 and already has the display included. It uses the newer RX63N MCU which is a better choice for a new project as it is easier to use than the RX62N. The kit include a debugger adapter that can be used for programming the device.

  • In reply to Gerald:

    Well, this seems a bit better solution.

    Why is 63N is easier to use than 62N? I thought they are the same. I see a 4.3" display with the kit... I want a bigger one like 7" or maybe 10" if I want to go that far. Can it do the job?

    I still insist to use the 99$ board xD. I will get it for a very cheap price (used), and I don't mind using an external controller or anything. Do you know how to do this?

    thanks friend.

  • In reply to VEGETA:

    In my opinion the I/O ports are easier to assign and configure for the RX63N.

    Sorry I can't help you with cheaper solutions. I think you will need to raise more money or settle for a simpler project.

  • In reply to Gerald:

    Well, I will get the 99$ board myself, as well as any required part. you don't have to help me get that at all.

    I just ask about the possibility to drive a TFF with a renesas RX board that doesn't have direct lcd features. It would still be a powerful MCU... so there must be a way to do it right?

    Also, does screen size has any relation to this?

  • In reply to VEGETA:

    The problem with driving a TFT display is you need to (1) have memory to store the screen, and (2) have hardware to get that data to the screen fast enough and with the right timing.  The TFT itself doesn't have any storage, it's like a VGA monitor.  So, you need something to store and stream the data.  DRAM is a cheap way to store the data, but now you need refresh cycles too.  The big RX chips (you need one with enough pins) have all that hardware built-in, and the EXDMA hardware knows how to stream the data from the DRAM to the TFT without interrupting your software.  It also maps the DRAM to your address space, so it's easy to access.  You could, in theory, use an FPGA or some other processor to manage the DRAM and TFT, but if you're doing custom work anyway, you might as well use the RX chip.  Betweek the RX chip and the DRAM you're probably spending around $30, including the little logic you'll need.  The TFT itself is up to you; size doesn't matter but pixels does (320x200 vs 640x480, for example) as more pixels means a faster data stream, which the hardware might not be able to do (I think it's a 10MHz dot clock limit, but you also need some cycles to update the data from your program ;).

    I've built my own boards using the FPGA option here: www.delorie.com/.../os-board.html (About $200 assembled, no they're not for sale)

    I still have some cheap 62N breakout boards that might work for you if you use the 144-pin chip: www.delorie.com/.../rx62n-breakout.html

    So if you don't mind doing some (or a lot) electronics, there are cheaper options than using a pre-existing SDK board.  Buying the $99 board would probably be a waste of money, as it has no way of getting data off the board fast enough to update the display, unless you get some "smart TFT module", which is itself a CPU that you're paying extra for and might as well just use instead of the RX.

  • In reply to DJ Delorie:

    DJ Delorie, thanks for your info.

    I already know that the 99$ doesn't have a built-in feature to drive the TFT. I just see some driver chips available and I wonder about using one of them with RX board... as I read that even weaker MCUs can use these driver chips to drive TFT displays.

    what do you think about it? so is this near your cheaper solutions?

  • In reply to VEGETA:

    also, i forgot to mention the software used in all this. I would need to use a free one as I don't intend to do fancy graphics and stuff.

    does the software used has any relation with the use of dev boards or driver chips?

    where to store all images? micro SD?

    thanks!

  • In reply to VEGETA:

    That depends on the driver chip and your requirements.  The biggest problem is bandwidth - getting data from your application to the TFT display fast enough to do what you want it to do.  The more "things" you have between you and the TFT, the slower the data will be, unless the data is somehow compressed.  I'm just thinking, if you're going to be doing custom electronics *anyway*, you might as well use the EXDMA solution and make it a lot easier and cheaper in the long run.  Otherwise, anything that will work with a small MCU will work with the RX also.

    As for software, you have a range of options, from Renesas's tools to GCC to others, and lots of OS options.

    MicroSD is big but really slow.  If you do use it, I suggest copying the data from there to RAM/DRAM if you can.

  • In reply to DJ Delorie:

    I have stated my requirements, so what about driver chips? I really don't know any. Plus, what is easier, the driver chips or direct drive?

    you mentioned EXDMA, is that a part of any affordable renesas boards? what is the difference between it and the direct drive lcd solution (that costs 770$)? If you want me to deal with bare chips (not dev boards), then I will need a programmer and other stuff that I am not aware of now.

    In the previous replies, he mentioned a 200$ kit from renesas which is the gui one. what do you think about it? does it have what is required to drive 7" display?

    as for software, I need a GUI design tool plus an OS. right now I don't know much about RTOS but they are in my plan (I have a timetable).

    If I shouldn't use a microSD, then use what to store stuff? as you know, there will be pictures and maybe other heavy stuff.

    thanks!

  • In reply to VEGETA:

    A quick google for "tft driver chip" or "tft driver board" will give you plenty of choices.  EXDMA is part of any 144-pin RX chip or bigger, so even my $6.25 breakout could to it.  However, the only Renesas SDK boards I've used (which was some time ago) that work with EXDMA are the ones that comes with a TFT, as all the other ones use those pins for other features that the boards are showing off.  SDK boards are designed to do "as much as possible" to let developers quickly evaluate various functions, so tend to be more expensive than special-purpose boards.

    As for the $200 board, perhaps you should read the "Product Overview" section and see for yourself.  I'm not going to read it for you.

    I didn't say "don't use microSD", I said you should consider copying the data off the microSD at startup so it will be faster to access it.  At least, for the commonly used graphics and sounds.

    I can't help you much with the software, but I do know that uC/OS and FreeRTOS both support the RX chip.