Created Sonoff B1 (markdown)

Sonoff-B1.md

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+Sonoff B1 R2 is the replacement for Sonoff B1 and can be programmed the same way as the B1. See [here](https://github.com/arendst/Sonoff-Tasmota/issues/3347#issuecomment-413579744) for more background information.
+
+## Serial Flashing
+
+Please see the [Hardware Preparation](https://github.com/arendst/Sonoff-Tasmota/wiki/Hardware-Preparation) page for general instructions.
+
+As always, you need to access the serial interface. First pop up the top part of the bulb with controlled force. The PCB as shown in the image will become visible.
+
+
+<img alt="Sonoff B1 PCB" src="https://user-images.githubusercontent.com/174291/51180848-dacef480-18c9-11e9-9390-ed294dfc77b5.jpg" width="60%" align="right" />
+
+<img alt="Sonoff B1 PCB" src="https://user-images.githubusercontent.com/174291/51180849-db678b00-18c9-11e9-8ac7-be43f6c71790.jpg" width="60%" align="right" />
+
+The **four serial pins** (3V3, RX, TX, GND) as well as the GPIO0 signal line are available as test points and clearly marked. Solder wires to those or use pogo pins as you prefer.
+
+As with all modules pulling GPIO0 to GND is needed to put the chip in programming mode. You need to **connect GPIO0 and GND** during power up. An additional GND pad is available in the middle of the PCB.
+
+**NOTE:** The **B1 R2** needs the GPIO0 connected to the GND pad in the middle of the PCB. Otherwise it won't enter flash mode. 
+
+### LED HEX10 Color Codes
+The Sonoff B1 uses a TEN charter HEX code for all colors. 
+Colors tested with firmware 5.9.1 20171107:
+* 00000000A0 = WARM
+* 000000A000 = COOL
+* 0000A00000 = BLUE
+* FF14500000 = PURPLE
+* 551A8B0000 = DARK PURPLE
+* A300000000 = RED
+* 00ff000000 = GREEN
+
+## Official Sources
+
+* Itead Product Page: http://sonoff.itead.cc/en/products/residential/sonoff-b1
+* Itead Shop: https://www.itead.cc/sonoff-b1.html
+* Itead Wiki: (not available)