IF i2c_clock_50'EVENT AND i2c_clock_50 = '1' THEN
     
        IF (i2c_clk_en = '1') THEN
            i2c_scl <= clk_i2c;
        ELSE
            i2c_scl <= '1';
        END IF;
         
         
        -- ack on SCL = HIGH
        IF (ack_en = '1') THEN
         
            CASE i2c_fsm IS
             
                WHEN st3 => -- get ack
                 
                        IF (i2c_sda = '0') THEN
                            i2c_fsm <= st4;      --ack
                            data_index <= 15;
                        ELSE
                            i2c_clk_en <= '0';
                            i2c_fsm <= st0;      --nack
                        END IF;
                     
                 
                WHEN st5 => -- get ack
                 
                 
                        IF (i2c_sda = '0') THEN
                            i2c_fsm <= st6;          --ack
                            data_index <= 7;
                        ELSE
                            i2c_fsm <= st0;          --nack
                            i2c_clk_en <= '0';
                        END IF;
                         
                         
                WHEN st7 => -- get ack
                 
                 
                        IF (i2c_sda = '0') THEN
                            i2c_fsm <= st8;          -- ack  --st8 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
                        ELSE
                            i2c_fsm <= st0;          --nack
                            i2c_clk_en <= '0';
                        END IF;
                         
                         
                WHEN OTHERS => NULL;
            END CASE;
        END IF;
         
         
        IF (clk_en = '1') THEN
         
            CASE i2c_fsm IS
             
                WHEN st0 => -- stand by
                 
                    i2c_sda <= '1';
                    i2c_busy <= '0';
                    i2c_done <= '0';
                     
                    IF (i2c_send_flag = '1') THEN
                        i2c_fsm <= st1;
                        i2c_busy <= '1';
                    END IF;
                     
                     
                WHEN st1 => -- start condition
                 
                    i2c_sda <= '0';
                    i2c_fsm <= st2;
                    data_index <= 7;
                     
                 
                 
                WHEN st2 => -- send addr
                 
                    i2c_clk_en <= '1'; --start clocking i2c_scl
                     
                    IF (data_index > 0) THEN
                        data_index <= data_index - 1;
                        i2c_sda <= i2c_addr(data_index);
                    ELSE
                        i2c_sda <= i2c_addr(data_index);
                        get_ack <= '1';
                    END IF;
                     
                    IF (get_ack = '1') THEN
                        get_ack <= '0';
                        i2c_fsm <= st3;
                        i2c_sda <= 'Z';
                    END IF;
                     
                     
                WHEN st4 => -- send 1st 8 bit
                 
                 
                    IF (data_index > 8) THEN
                        data_index <= data_index - 1;
                        i2c_sda <= i2c_data(data_index);
                    ELSE
                        i2c_sda <= i2c_data(data_index);
                        get_ack <= '1';
                    END IF;
                     
                    IF (get_ack = '1') THEN
                        get_ack <= '0';
                        i2c_fsm <= st5;
                        i2c_sda <= 'Z';
                    END IF;
                     
                     
                WHEN st6 => -- send 2nd 8 bit
                 
                 
                    IF (data_index >0) THEN
                        data_index <= data_index - 1;
                        i2c_sda <= i2c_data(data_index);
                    ELSE
                        i2c_sda <= i2c_data(data_index);
                        get_ack <= '1';
                    END IF;
                     
                    IF (get_ack = '1') THEN
                        get_ack <= '0';
                        i2c_fsm <= st7;
                        i2c_sda <= 'Z';
                    END IF;
                     
                     
                WHEN st8 => -- stop condition
                 
                 
                    i2c_clk_en <= '0';
                    i2c_sda <= '0';
                    i2c_fsm <= st0;
                    i2c_done <= '1';
                 
                 
                WHEN OTHERS => NULL;
            END CASE;
        END IF;