What is it? -- This a Universal USB to Serial upload adapter for Arduino Boards, similar to the FTDI, CP2102 or CH340G based modules.

Why did I design it? -- I needed an adapter to use with all my Arduino boards, be they proMinis or barebones ESP-12, ESP-01 etc.

What makes it special? -- The ESP series of MCUs require manipulation of 2 separate pins to enter and exit bootload mode. Some of them have 2 button for this purpose, and others also have a special circuit to do this automatically. If you are doing work with bare ESP modules like the ESP-01, -07 or -12 etc, you have to play with jumpers or setup your own switches to up load code. This module has jumpers and the special circuitry to enable automatic uploading.

The module uses the CP2102 which has the DTR and RTS signals available to implement the special circuit needed to get in and out of bootload mode. A pair of jumpers is provided to select this circuitry. Installing the jumpers in the "ESP" position provides the correct Reset signal on the DTR pin, and the required GPIO0 signal on the RTS pin. Installing them in the AVR position will allow the module to work as a regular CP2102 with Reset output on the DTR pin. (The jumper for the RTS pin can be left off - it is not used by AVR MCUs like the proMINI.)

Although the CP2102 has an internal 3V3 regulator it is not always sufficient for beefier MCUs such as the ESP32 and even some ESP8266 modules. For this reason I have included a LMS1117 850mA separate regulator which will also be useful if you are powering additional modules. There is a jumper provided to select the raw 5V Vcc from the USB or the regulator output.

There are solder pads on the bottom of the board to enable the TX and RX LEDs. They can interfere with more esoteric uses of the board such as jury rigging an UPDI programmer for AVR128s and many of the very new MCUs from MicroChip. (next version of this module will include the jury rig as an option)