stm32f4 and PSRAM

Posted on April 27, 2013 at 20:09

The address increments by two because 16-bit contains TWO 8-bit bytes. The address inside the CPU is for bytes. It is a byte offset.

You know you can read/write to it like normal memory?

uint16_t *p = (uint16_t *)0x64000000; // As a pointer to 16-bit WORDS

p[0] = 0x1234;

p[1] = 0x5678;

p[2] = 0x9ABC;

p[3] = 0xDEF0;

printf(''%04X\n'',p[0]);

printf(''%04X\n'',p[1]);

printf(''%04X\n'',p[2]);

printf(''%04X\n'',p[3]);

uint8_t *q = (uint8_t *)0x64000000; // As a pointer to 8-bit BYTES

printf(''%02X\n'',q[0]);

printf(''%02X\n'',q[1]);

printf(''%02X\n'',q[2]);

printf(''%02X\n'',q[3]);

The RAM should extent 0x64000000..0x647FFFFF

ie through p[0x3FFFFF] or q[0x7FFFFF]

Posted on April 28, 2013 at 09:11

Thank you Clive :)

I understand a little more now.

I have do this test :

void test_Clive_ram(void)

{

uint8_t ReadRam[4] = {0};

uint16_t *p = (uint16_t *)Bank1_SRAM2_ADDR; // As a pointer to 16-bit WORDS

uint8_t *q = (uint8_t *)Bank1_SRAM2_ADDR; // As a pointer to 8-bit BYTES

p[0] = 0x1234;

p[2] = 0x5678;

p[4] = 0x9ABC;

p[6] = 0xDEF0;

ReadRam[0] = q[0]; // Result is : 0x34

ReadRam[1] = q[1]; // Result is : 0x12

ReadRam[2] = q[2]; // Result is : 0x78

ReadRam[3] = q[3]; // Result is : 0x56

}

I see that the data are LSB first ...

My point was to use the PSRAM as a little buffer for a TFT screen (SSD1963 480 x 272).

I get the rest of the components and will be able to use the board i have made at end of the

week day's.

As i understand a little more now i will have to use a step of 2 for the address because the data

i have to send to the screen controller are in 16bits.

It's just 2M x 16bits but better than nothing .....

I will have to look how the DMA work and prey that it can handle a step of 2 for the address too

so i can use it in background to send pixels continuously to the screen ;)

You can see the old board i made here :

http://www.youtube.com/watch?v=tx9YSFPpKLw&list=UUPP_IrS9eBG80PxEURo0Ctw&index=1

I made hw mistake with the memory and cant use it on that board.

It use a Core407i from waveshare.

The actual board i use is the HY-STM32F4xxCore144 from here :

http://www.hotmcu.com/hystm32f4xxcore144-coredev-board-p-10.html

So i don't have to solder any memory and don't made error again ;)

Anyway many thanks for your advice and i hope that my Frenglish language is

not too bad.

Cheers.

Posted on February 25, 2014 at 13:54

Hello darth,

did You use the HY_Board?

I run into trouble use that board with stemwin gui and the ps ram.  It is hard to debug because the trouble seems to be in the precompiled lib.