ESP8266 Community Forum

Hello friends, a couple of questions

Question 1
I noticed that the bundled AT firmware that comes with the IOT_SDK changed from being made for 512kB flash in 1.0.0 to 1024kB in 1.0.1 and above. But for older devices, which, all have 512kB flash - are we supposed to compile AT firmware ourselves? (Not a hard thing to do, just asking for clarification )

Question 2
How does one go about establishing the size of their flash chip? Using esptool I can see something like:


But of course, that doesn't include the size. Searching this board led me to identify my flash as:

Is there an easier way to do this?

Ok, so I think I can answer (1) by myself. Here are the sizes of the binaries (rom), as compiled with default settings (-g -Os -O2) in Espressif's makefile:



Here are the maximum rom sizes, depending on flash configuration.



Single slot has no second stage bootloader section, and uses most of the flash for storing just one rom (libs+user). The dual slot needs a second stage bootloader and the remaining space is split in two. Thus, the stock AT will just barely not fit into a 512kB flash in a dual slot setup. For this reason, it has been shipped as compiled for a larger (1024kB) flash in a dual slot setup.

There you have it. If you've got an older device with a 512kB flash (which most of them currently are) and you want fresh AT firmware you have to:

1. Compile yourself
2. Compile as single slot (no OTA)

New wrinkle:

When I write the flash.bin and irom0text.bin to 0x0 and 0x40000, respectively - I get only bootloader output. In other words - something is broken in the usercode.

After flashing with:


I read back with:


And sure enough! The first 0x5000 bytes are erased (all FF's), whereas in flash.bin the first 0x5000 bytes are valid/normal/magic number/etc.

What is going on?

Some experiment results:



What gives? Is this an esptool.py bug?