ESP8266 Community Forum

- Fri Apr 15, 2016 7:12 am #45520 Thanks for the directions lethe, it is of great help!
Now during startup I read the first four bytes of address 0x00 of the flash.
If it reads 0xE9030060, this means the mode is QIO, and I write back 0xE9030260 to set it to DIO.
If it already has been set to DIO, I don't write anything.
This really seems to work well!
Just a small summary:

Code: Select all0xE9         03      02         60
Magic value   ?      SPI Mode   Size(high nibble)&   Speed(low nibble)
                     00: QIO    0x: 512kB (256x2)    x0: 40 MHz
                     01: QOUT   1x: 256kB            x1: 26,67 MHz
                     02: DIO    2x: 1MB (512x2)      x2: 20 MHz
                     03: DOUT   3x: 2MB (512x2)      xf: 80 MHz
                                4x: 4MB (512x2)
                                5x: 2MB (1024x2)
                                6x: 4MB (1024x2)


One more thing I can't seem to figure out:
I have to erase the whole first sector(4kB), before I can write to it.
This means I first have to read 4096 Bytes to a buffer, change the 3rd Byte and write the whole thing back.
Is there a way which would not consume this many RAM?
I know I can do a os_zalloc and then free the whole block, but I'd rather not.

Code: Select allspi_flash_read(0x0 * SPI_FLASH_SEC_SIZE, (uint32 *)buff, 4096);
os_printf("0x0 sec:%02x%02x%02x%02x\r\n", buff[0], buff[1], buff[2], buff[3]);
if((buff[2] != 0x02) || buff[3] != 0x60)
{
   os_printf("Flash is not set to DIO or 4MB+40MHz. Correcting settings...\n\r");
   buff[0] = 0xE9;
   buff[1] = 0x03;
   buff[2] = 0x02;
   buff[3] = 0x60;
   spi_flash_erase_sector(0x0);
   result = spi_flash_write(0x0 * SPI_FLASH_SEC_SIZE, (uint32 *)&buff[0], 4096);
   os_printf("Result: %d\n\r", result);
}
else
{
   os_printf("Flash settings are quitte allright\n\r");
}


- Fri Apr 15, 2016 11:21 am #45543 You have to read & write the entire 4k sector, since you can only erase whole sectors (due to the way NOR flash hardware works).
So you have to use os_malloc()/os_free(), unless you are ok with wasting 4k of RAM permanently.