It is written in the docs that the dct sector of photon is mapped to a separate dfu media device to enable updating the dct contents independently. Can anyone please elaborate this? I really cannot get the mapping to dfu media device.
Also, please kindly explain the following contents in the dct.
led mirror and led theme
alt server address
P.S: I am a newbie and I really need to understand the memory map correctly. So, please guide me through this!!
The alt server address and keys aren’t used on the Photon. It’s only used on the Electron and E series.
When you use DFU mode and special the -a 1 flag to dfu-util it writes to the alt DFU mapping, which is the DCT. The address is then relative to start of the DCT, so the numbers in the data sheet will match up with what you specify to dfu-util.
There are two sectors of flash memory for the DCT. One is the active one and the other is typically erased to 0xFFs. Whenever you write to the DCT, the entire thing is copied to the other sector with the changes, as flash memory can only be erased at the sector level.
Thanks @rickkas7 for your answer.
But, If alt server address is not used in photon, where is actually the server address stored in photon?
And could you please explain what is actually stored in the led mirror (I now know what is stored in the led theme)?