Start adding esp32 sketch

esp32/README.md

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+This module includes an arduino sketch designed to run on the ESP32.
+
+The sketch takes simple input from serial (ESP32 microusb port), and converts the input to a duty cycle that can be used on servos.
+
+The protocol specification is as follows, assuming an array of bytes:
+
+
+| Byte Number   | Value Description |
+| :---------- |  ----------: |
+| 0 | 0 if Calibrating a servo. Higher values indicates channel number to set duty cycle on. |
+| 1 | If byte 0 = 0: number of servos to calibrate. Else, the new duty cycle value for the channel specified in byte 0. |
+
+The table below describes the byte format for calibrating a servo. This array of bytes can be repeated for the given number of servos in byte 1:
+
+| Byte Number   | Value Description |
+| :----------   |  ----------:      |
+| 0             | Servo channel to set (this will be byte 0 when setting duty cycle, so don't use 0). |
+| 1             | The pin number to setup |
+| 2             | The frequency for the pin |
+
+The min/max pulse widths are hardcoded to 1000us/2000us respectively. 
+
+At the end of each loop, the entire array will be read, to flush any data that may cause issues later.