This command retrieves the certificate of the device which it created a PKI connection to. 
- Returns
 - BRP_OK on success or BRP_ERR_BUFFER_OVERFLOW if dev_cert_buf_size is smaller than the device certificates actual size. 
 
- Parameters
 - 
  
    | protocol | an opened pki protocol handle  | 
    | dev_cert_buf | a pointer to a buffer, where the device's certificate shall be returned. Will only be written if BRP_OK is returned. May be NULL if dev_cert_buf_size is 0.  | 
    | dev_cert_buf_size | the size of 'dev_cert_buf'  | 
    | dev_cert_len | returns the actual size of the certificate. Will be even set to the actual size of the certificate, if dev_cert_buf_size is smaller.  |