Which type of non-basic cipher works better with microcontroller which has no interface and keyboard connected to it? Did a C++ code on Caesar Cipher to do encryption and decryption with my XMC4500 microcontroller but my lecturer said that Caesar Cipher is too simple. He wants me to use a non basic type of cipher and to include size of bit length of plain text and cipher text, secret and public message number and key. And the problem is no keyboard or display interface will be connected to my microcontroller so i could not use printf, scanf, cout and cin to input any of those values. Any ideas on what Cipher I should use and how I could do it?

UPDATE: Thank you for all the suggestions but my supervisor finally told me to use ASCON instead.
That's a 32 bit ARM chip (M4), but without any hardware based crypto capabilities. That means that the best choice of a cipher is one that runs best on 32 bit CPU's, e.g. ChaCha20, SOSEMANUK or NORX (taken from this answer by Thomas). Of course for transport security you may want to use authenticated encryption, but you can always bold that on (this seems to be an assignment after all).

Above ciphers are good ciphers to try to implement yourself. However, if there are ciphers available in libraries then you may want to use those and safe yourself a lot of time. Before implementing a cipher, make sure that this is the purpose of the assignment!

Note that a cipher in itself does not offer security. You need a security design for your system for that.