At the link below you can download the source code to run the Enigma algorithm in an Arduino.
Enigma thru serial port
Download the file called EnigmaSerial.ino
The machine settings are initialized in the initEnigma() function, the wheel types, rotor positions, ring settings, plugboard and Uhr are initialized there.
In the loop function, the serial port is read, if the special character ! is sent, the next characters will be used as rotor positions. Then the machine will encode a character.
This will allow you to have an external device to the computer performing the enigma encryption.
This is the same engine used in the Arduino Enigma Machine Simulator.
This open enigma engine has been used to create several enigma machines. arduinoenigma.blogspot.com/2015/10/projects-made-with-arduino-enigma.html