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LPC1788 board & porting


#1

Hello,

With al lot of fun I use the EMX module, only I see that I have problems when using a a 800x480 TFT screen. The screen is works ok, but when I use the sd card to read a bmp file, you see the TFT screen flickering.
The solution should be to change the lcd clock, but when I do that you some litte flickering in the screen. Also an screen update from the sd card cost a lot of time, more then 5 seconds.

The strange of the story is, when I use an USB stick to read a bitmap file, the flickering is not present and also I can use the good lcd clock speed. But the time to show an picture is very slow.

So I looked and saw that NXP has an new microcontroller the LPC1788 @ 120Mhz and SDRAM clock @ 80Mhz.

My idea is to make a board with a 16-bit flash and a 32-bit SDRAM and the LPC1788, the advantage I think is the use of 32-bit SDRAM this will give an lower load on the LCD bus, so the programm can works faster.

The question is, is it already possible to port the micro frame work to the LPC1788 and are the any suggestions for this board?

Thanks

Patrick


#2

We had LPC1788 running our EMX firmware about a year ago already :slight_smile: The results were disappointing! It was not faster by anything usable.

Long story short, ARM7/cortex do not have cache so a faster clock (120mha vs 72mhz) didn’t make any difference as the SDRAM bus speed (the bottleneck) is the same on both chips. The faster chip spent most of its time waiting for SDRAM, add a 800x480 display on SDRAM and things get even more disappointing.

The only way to go faster than EMX on today’s processors is to go with ARM9…here, I saved you few months of work :slight_smile:


#3

ARM9, you say, sounds like you need a ChipworkX!


#4

@ Gus, can you maybe do a wiki or just run us through some learnings on porting? What works and what doesn’t?

I’m also curious why NETMF is not going beyond ARM to RISC processors. 15 cycles per instruction vs. 1 to 4 seem to be something that could make a big difference on tiny devices.

.Net Nano Framework? :slight_smile:


#5

You mean this? http://wiki.tinyclr.com/index.php?title=Category:Beginner_Porting_Guide_ebook


#6

Gus, thank you for your reply.

I realy tought that the LPC1788 can be faster, but the coming NXP processor LPC1857. I read that this on have a cpu clock of 150Mhz and a SDRAM clock of 120Mhz.

Would this be faster or must the ARM9 or ARM11 the next step