I hope I clarify things with my answer here:
The ESP-WROOM-02 is a module based on the ESP8266. The main purpose of this module is to give you a small subsystem or module that you can directly place into your applcaition without having to bother about designing a chip antenna and dealing with RF circuit design!
What does the ESP-WROOM-02 contain?
It contains the ESP8266 SoC, which contains the entire RF transceiver circuit on the silicon die. The ESP8266 chip thus has a 32-bit Xtensa core which interfaces to the on-chip WiFi block via the usual way SoC cores access peripherals (i.e. address bus, data bus, registers... etc).
The WROOM-02 also contains a flash memory chip to store the user program... and a crystal oscillator to clock the ESP8266. So there are these 2 chips and a crystal inside + some discrete cmoponents!
Can you access the WiFi peripheral using registers?
No! We provide SDK APIs and functions for that. The main code is confidential because we don't want people to be messing around with a programmable 2.4GHz radio and render all other WiFi networks in the area useless by transmitting gibberish with a buggy software!
Also, messing with the internal parameters may potentially cause permanent damage to the chip in some cases.
How is the flash connected to the ESP8266?
The flash chip inside the WROOM-02 module uses the SPI interface to connect to ESP8266.Statistics: Posted by Guest — Sat Nov 19, 2016 1:29 pm
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