How to create Self signed certs/keys for both server and client?

Mbed TLS
1

Hi
I am new to MbedTLS using on STM32. We want to use self signed certificates for both device and server.

  1. How to create self signed cert/key for both test server and test device.

We want to fix the cipher suit to say ECDHE-RSA-AES256-GCM-SHA256 , and cut down the handshake flow and provide server/client authentication and encryption/decryption and HMAC. We understand like, for server authentication …we need to use RSA as per cipher suit, handshake with ECDHE…
2. What are the core mbedTLS api to achieve the above security w.r.t cipher suit mentioned.