Using "high ram"?

Pokitto Programming
1

Hi, is there any example how to use “HIGH RAM” for own data? I know I need to say in my_settings.h:
#define PROJ_HIGH_RAM HIGH_RAM_ON

But then what? In which address that is usable? Can I copy data normally using memcpy() between the high ram and the normal ram?

2

I can’t remember for sure, but if you dig around the Pokittolib source, the music code just uses a pointer to that memory location I think.

3

Something like this…

unsigned char *myBuffer = (unsigned char *) 0x20000000;
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4

I used both in PtaD like so

constexpr uint32_t HIGH_RAM1 = 0x20000000;
constexpr uint32_t HIGH_RAM2 = 0x20004000;

Then its just defining pointers and setting their address to an offset into either HIGH_RAM1 or HIGH_RAM2 like this:

constexpr uint32_t TILEMAPBG_MEMORY_ADDRESS = HIGH_RAM1;
constexpr uint32_t TILEMAPFG_MEMORY_ADDRESS = HIGH_RAM1 + TILEMAP_MEMORY_SIZE;

uint8_t *PTAD::tilemapBG = (uint8_t*)PTAD::TILEMAPBG_MEMORY_ADDRESS;
uint8_t *PTAD::tilemapFG = (uint8_t*)PTAD::TILEMAPFG_MEMORY_ADDRESS;

Here both my background and foreground tilemaps are stored sequentially in HIGH_RAM1.

3 Likes
5

the ld file contain what you need to declare any var to be into others ram chip :

MEMORY
{
...
Ram1_2 (rwx) : ORIGIN = 0x20000000, LENGTH = 0x800 /* 2K bytes */
Ram2USB_2 (rwx) : ORIGIN = 0x20004000, LENGTH = 0x800 /* 2K bytes */
...
}
...
    /* possible MTB section for Ram1_2 */
    .mtb_buffer_RAM2 (NOLOAD) :
    {...
    } > Ram1_2 
    
    /* DATA section for Ram1_2 */
    .data_RAM2 : ALIGN(4)
    {...
    } > Ram1_2 AT>MFlash256
    /* possible MTB section for Ram2USB_2 */
    .mtb_buffer_RAM3 (NOLOAD) :
    {...
    } > Ram2USB_2 
    
    /* DATA section for Ram2USB_2 */
    .data_RAM3 : ALIGN(4)
    {...
    } > Ram2USB_2 AT>MFlash256

so you may check using theses sections for your variables definitions, using gcc attribute section way :

int myvar __attribute__((section (".mysection"))) ;

_ . -

yet for my own projects i wasn’t able to properly use these (as i lack too much about some asm and low level basis like “data” “mtb” “bss” and so lol) so i redeclared sections into my ld file ( gm0/LPC11U68.ld at main · r043v/gm0 · GitHub

MEMORY
{
...
  SRAM  (rwx) : ORIGIN = 0x20000000, LENGTH = 0x800
  USBSRAM (rwx) : ORIGIN = 0x20004000, LENGTH = 0x800
}
...
  __top_SRAM = 0x20000000 + 0x800;
  __top_USBSRAM = 0x20004000 + 0x800;
...
SECTIONS
{
...
  .sram :
  {
    . = ALIGN(4);
    __sram_start__ = .;
	*(.sram*)
    __sram_end__ = .;
  } > SRAM AT>MFlash256

  .usbsram :
  {
    . = ALIGN(4);
    __usbsram_start__ = .;
	*(.usbsram*)
    __usbsram_end__ = .;
  } > USBSRAM AT>MFlash256
...
}

and i use them in my code with these :

u8 gfxBank[16*16*4] __attribute__((section (".sram"))) ;
u32 rgfxBank32[16*16] __attribute__((section (".usbsram"))) ;
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