SPI Flash

linas2 · ‎2012-05-31

Posted on May 31, 2012 at 10:04

Hello

I am working on LCD project (Fractals) and i need large buffer for storing iteration values, so i can calculate fractal and when paint it.

I need to store 8b number, total of 130560. so what would be around 1Mb.

I have W25Q16 flash below my lcd, i remade code from ST SPI sampl, but don't know how to write individual numbers and then read them.

i guess i have to use this function:

/* Write Tx_Buffer data to SPI FLASH memory */

sFLASH_WriteBuffer(Tx_Buffer, FLASH_WRITE_ADDRESS, BufferSize);

/* Read data from SPI FLASH memory */

sFLASH_ReadBuffer(Rx_Buffer, FLASH_READ_ADDRESS, BufferSize);

But what kind of C syntax that would be?

code is like this

int h=0;

u32 i =0;

while(i<(480*272))

{

h=fractal iteration number ;//0-255

sFLASH_WriteBuffer(h, i, 1);

i++;

}

i=0;

int x=,y=0;

while(x<480)

{

while(y<272)

{

sFLASH_ReadBuffer(&h, i, 1);

LCD_Pixel(x,y,asemble_rgb(h)):

y++;

i++;

}

y=0;

x++;

}

Help is highly appreciated

#stm32f4-fsmc-lcd-tft-ssd1963

frankmeyer9 · ‎2012-05-31

Posted on May 31, 2012 at 13:27

I believe Flash is NOT what you want for this purpose.

First, it has a limited number of erase/write cycles, usually about 10.000 cycles.

It would not take long until you run into problems, because the cells can't be written anymore.

Second, a Flash write takes long (several milliseconds), the erase you need before takes even longer - about.200ms

Flash is for values which are rarely changed, and mostly read.

For intermediate values things like iteration variables, you would need RAM.

frankmeyer9 · ‎2012-05-31

Posted on May 31, 2012 at 20:18

The more I tinker with it, the less appealing I find this idea.

while(i<(480*272))
{ 
h=fractal iteration number ;//0-255
sFLASH_WriteBuffer(h, i, 1);
i++;
}

What would be the runtime of this loop, when each (serial) write access consumes several milliseconds, and adding the erase delay for each block of ..250ms ? If you intend to use an stm32f4, why not taking advantage of the FSMC, i.e. the external memory interface ? Or, use a Cortex A8 device or similiar, if you need more RAM and performance.

linas2 · ‎2012-06-02

Posted on June 02, 2012 at 17:57

i would love to use cortex A8, but i don't know where to find something that you can solder at home to pcb.

i guess i will buy some ram and use same fsmc line as lcd

max speed for this type of processor is 250MHz (texas Hercules m4 core )

http://www.youtube.com/watch?v=j2dKBz2jUt0