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What determines the properties of the SPI flash: hardware or software ?

Posted: Fri Jun 22, 2018 6:04 pm
by Pato
Hey folks,

It's still unclear for me. When generating an image for the ESP or when flashing it, we are asked to indicate what flash map, which SPI mode and which SPI frequency we want to use. This info is then included in the header of the image. My question is:

Do we have to select the values that matches our hardware, i.e. it's the flash module that imposes these properties and it won't work corresctly with if we selected the wrong mode for example ?
OR
Do the value I selected will be applied and will make the SPI flash operate at the mode and frequency I set ?

In the same idea, if I have a 4M flash, can I select 512+512 map like 1024+1024 if I want to burn a larger software ? (or is the map also imposed by the hardware ?)

Thanks !

Re: What determines the properties of the SPI flash: hardware or software ?

Posted: Fri Jun 22, 2018 9:47 pm
by blubb
You have to set the values according to your hardware. The chip reads the values in a fail-safe default mode upon boot and then switches to the given mode. Likewise it expects the images to be at the positions based on your flash map setting.

https://github.com/espressif/esptool/wi ... age-Format
https://github.com/espressif/esptool/wi ... lash-Modes

Re: What determines the properties of the SPI flash: hardware or software ?

Posted: Tue Jun 26, 2018 3:39 pm
by Pato
Okay, thanks to have made it clear !