94 lines
4.5 KiB
ReStructuredText
94 lines
4.5 KiB
ReStructuredText
General information about the ESP8266 port
|
|
==========================================
|
|
|
|
ESP8266 is a popular WiFi-enabled System-on-Chip (SoC) by Espressif Systems.
|
|
|
|
Multitude of boards
|
|
-------------------
|
|
|
|
There are multitude of modules and boards from different sources which carry
|
|
ESP8266 chip. MicroPython tries to provide a generic port which would run on
|
|
as many boards/modules as possible, but there may be limitations. Adafruit
|
|
Feather HUZZAH board is taken as a reference board for the port (for example,
|
|
testing is performed on it). If you have another board, please make sure you
|
|
have datasheet, schematics and other reference materials for your board
|
|
handy to look up various aspects of your board functioning.
|
|
|
|
To make a generic ESP8266 port and support as many boards as possible,
|
|
following design and implementation decision were made:
|
|
|
|
* GPIO pin numbering is based on ESP8266 chip numbering, not some "logical"
|
|
numbering of a particular board. Please have manual/pin diagram of your board
|
|
handy to find correspondce between your board pins and actual ESP8266 pins.
|
|
We also encourage users of various boards to share this mapping via MicroPython
|
|
forum, with the idea to collect community-maintained reference materials
|
|
eventually.
|
|
* All pins which make sense to support, are supported by MicroPython
|
|
(for example, we don't expose pins which are used to connect SPI flash
|
|
are not exposed, as they're unlikely useful for anything else, and
|
|
operating on them will lead to board lock-up). However, any particular
|
|
board may expose only subset of pins. Consult your board reference manual.
|
|
* Some boards may lack external pins/internal connectivity to support
|
|
ESP8266 deepsleep mode.
|
|
|
|
|
|
Technical specifications and SoC datasheets
|
|
-------------------------------------------
|
|
|
|
The datasheets and other reference material for ESP8266 chip are available
|
|
from the vendor site: http://bbs.espressif.com/viewtopic.php?f=67&t=225 .
|
|
The are primary reference for the chip technical specifications, capabilities,
|
|
operating modes, internal functioning, etc.
|
|
|
|
For your convinience, some of technical specifications are provided below:
|
|
|
|
* Architecture: Xtensa lx106
|
|
* CPU frequency: 80MHz overclockable to 160MHz
|
|
* Total RAM available: 96KB (part of it reserved for system)
|
|
* BootROM: 64KB
|
|
* Internal FlashROM: None
|
|
* External FlashROM: code and data, via SPI Flash. Normal sizes 512KB-4MB.
|
|
* GPIO: 16 + 1 (GPIOs are multiplexed with other functions, including
|
|
external FlashROM, UART, deep sleep wake-up, etc.)
|
|
* UART: One RX/TX UART (no hardware handshaking), one TX-only UART.
|
|
* SPI: 2 SPI interfaces (one used for FlashROM).
|
|
* I2C: No native extenal I2C (bitbang implementation available on any pins).
|
|
* I2S: 1.
|
|
* Programming: using BootROM bootloader from UART. Due to external FlashROM
|
|
and always-available BootROM bootloader, ESP8266 is not brickable.
|
|
|
|
|
|
Boot process
|
|
------------
|
|
|
|
On boot, MicroPython EPS8266 port executes ``_boot.py`` script from internal
|
|
frozen modules. It mounts filesystem in FlashROM, or if it's not available,
|
|
performs first-time setup of the module and creates the filesystem. This
|
|
part of boot process is considered fixed, and not available for customization
|
|
for end users (even if you build from source, please refrain from changes to
|
|
it; customization of early boot process is available only to advanced users
|
|
and developers, who can diagnose themselves any issues arising from
|
|
modifying the standard process).
|
|
|
|
Once filesystem is mounted, ``boot.py`` is executed from it. The standard
|
|
version of this file is created during first-time module set up and by
|
|
defaults starts up a WebREPL daemon to handle incoming connections. This
|
|
file is customizable by end users (for example, you may want to disable
|
|
WebREPL for extra security, or add other services which should be run on
|
|
module start-up). But keep in mind that incorrect modifications to boot.py
|
|
may still lead to boot loops or lock ups, requiring to reflash a module
|
|
from scratch.
|
|
|
|
As a final step of boot procedure, ``main.py`` is executed from filesystem,
|
|
if exists. This file is a hook to start up a user application each time
|
|
on boot (instead of going to REPL). For small test applications, you may
|
|
name them directly as ``main.py``, and upload to module, but instead it's
|
|
recommended to keep your application(s) in separate files, and have just
|
|
the following in ``main.py``::
|
|
|
|
import my_app
|
|
my_app.main()
|
|
|
|
This will allow to keep structure of your application clear, as well as
|
|
allow to install multiple applications on a board, and switch among them.
|