/**

@defgroup    boards_esp8266_sparkfun-thing SparkFun ESP8266 Thing
@ingroup     boards_esp8266
@brief       Support for the SparkFun ESP8266 Thing modules.

## Overview

The [SparkFun ESP8266 Thing](https://www.sparkfun.com/products/13231) and
[SparkFun ESP8266 Thing DEV](https://www.sparkfun.com/products/13711) are
low-cost and easy to use breakout and development boards for the ESP8266.
Both SparkFun ESP8266 Thing boards are relatively simple boards. The pins
are simply broken out to two parallel, breadboard-compatible rows.

@image html "https://gitlab.com/gschorcht/RIOT.wiki-Images/raw/master/esp8266/Sparkfun_Thing_x.png" "SparkFun ESP8266 Thing (left) / SparkFun ESP8266 Thing DEV (right)"

## Hardware

### MCU

Most features of the board are provided by the ESP8266EX SoC.

<center>

MCU         | ESP8266EX
------------|----------------------------
Family      | Tensilica Xtensa LX106
Vendor      | Espressif
RAM         | 80 kByte
Flash       | 512 kByte
Frequency   | 80 / 160 MHz
FPU         | no
Timers      | 1 x 32 bit
ADCs        | 1 x 10 bit (1 channel)
LEDs        | 1 x GPIO1
I2Cs        | 2 (software implementation)
SPIs        | 1
UARTs       | 1 (console)
WiFi        | built in
Vcc         | 2.5 - 3.6 V
Datasheet   | [Datasheet](https://www.espressif.com/sites/default/files/documentation/0a-esp8266ex_datasheet_en.pdf)
Technical Reference | [Technical Reference](https://www.espressif.com/sites/default/files/documentation/esp8266-technical_reference_en.pdf)
Board Schematic | [ESP8266 Thing](https://cdn.sparkfun.com/datasheets/Wireless/WiFi/SparkFun_ESP8266_Thing.pdf)\n [ESP8266 Thing Dev](https://cdn.sparkfun.com/datasheets/Wireless/WiFi/ESP8266-Thing-Dev-v10.pdf)

</center>

### Board Versions

Although the board definition works with both boards, it's important
to know that they differ slightly in some features:

<center>

Feature                        | ESP8266 Thing | ESP8266 Thing Dev
-------------------------------|---------------|------------------
USB to Serial adapter on-board | no            | yes
I2C pull-up resistors on-board | yes (jumpable)| no [1]
Programming interface          | FTDI USB to Serial adapter | USB
Reset/Flash/Boot logic         | FTDI          | USB
Battery connector              | yes           | no (can be retrofitted)
LiPo Charger on-board          | yes           | no
LED (GPIO5)                    | high active   | low active [2]
GPIO15 broken out              | no            | yes
CHIP_EN broken out             | yes           | no

</center>

[1] Although the SparkFun ESP8266 Thing Dev has no on-board I2C pull-up
resistors, the I2C interface can be used because the ESP8266 SoC has
built-in pull-up resistors that are activated by the I2C peripheral driver.

[2] The board configuration defines high-active LEDs. If the
SparkFun ESP8266 Thing Dev is used with this board configuration,
the LED outputs must be inverted by the application.

### RIOT Pin Mapping

The following figures show the mapping of these pin holes to RIOT pins.

@image html "https://gitlab.com/gschorcht/RIOT.wiki-Images/raw/master/esp8266/Sparkfun_Thing_pinout.png" "SparkFun Thin Pinout"
\n

@image html "https://gitlab.com/gschorcht/RIOT.wiki-Images/raw/master/esp8266/Sparkfun_Thing_Dev_pinout.png" "SparkFun Thin Dev Pinout"
\n

Flash SPI pins including GPIO9 and GPIO10 are not broken out. The
SparkFun Thing board has solder pads for these pins at the bottom layer.

## Flashing the Device

To flash the RIOT image, the device has to be connected to the host computer.
Since the SparkFun Thing Dev board has an USB to Serial adapter on board,
this can done directly using the Micro USB. SparkFun Thin board has to be
connected to the host computer using the FTDI interface and a FTDI USB to
Serial adapter/cable. For more information on how to program the
SparkFun Thing board, please refer the
[ESP8266 Thing Hookup Guide](https://learn.sparkfun.com/tutorials/esp8266-thing-hookup-guide/programming-the-thing).

@note Please make sure the FTDI USB to Serial adapter/cable uses 3.3 V.

Both boards have a reset/flash/boot logic on-board so that flashing is
quite simple. To flash the RIOT image just type:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
make flash BOARD=esp8266-sparkfun-thing ...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For detailed information about ESP8266 as well as configuring and compiling
RIOT for ESP8266 boards, see \ref esp8266_riot.
*/