Happy Bison

ESP8266 Dev board around ESP-201 module

I recently came across ESP8266 WiFi chip and various modules based on it. This is a low cost microcontroller with WiFi built into it. There is a huge community around ESP8266. You can develop for it using C, Lua and even Wiring using Arduino development tools.

I decided to get my hands on it to play with it a little. I ordered some boards for a start. First, I needed some kind of easy prototyping dev board for easier testing. I got ESP-201 and Dev board designed specifically for it. After unsuccessful search looking for schematic to see how GPIO pins connected on it, I decided to trace it and make my own to share with others.

I traced it as much as I could, but it may have some bugs. If you find something, feel free to let me know. Update: I found similar schematics after I created my version, so I'll keep it here anyway.

Interesting thing is that CH340G is powered using 5V power and connected to RX/TX of ESP-201 module without any level shifters. At first, I did not know it and was able to test the board. So it seems like RX/TX are 5V tolerant after all.

Board features

The board has the following:

• USB Mini: power and serial communications
• USB Micro: power only. One USB can be connected at a time, not both
• AMS1117 3.3V LDO (capable up to 1A)
• Power on/off switch
• CH340G USB-RS232 bridge. You can by-pass it by using JP4/JP7 jumpers and JP2 connector
• Boot mode S2/S3 switches
• Switch block to connect/disconnect various load (LED, Relay, etc)
• RGB Led, White LED, Buzzer, Relay, Pot, DHT11 connector

The LEDs are very bright so I had to use PWM to lower the brightness.

Connections

Here is the connection table of all peripherals on the board:

Additionally, the switch block has K1 linking ground to GPIO 15, and K2 linking ground to GPIO 0 (for bootloader).