I2Cmaster with MPU6050 in VHDL not working

Question

For my hobby project I try to make a quadcopter which balances itself with the MPU-6050. The flight controller shall be the FPGA Altera cyclone IV, because its fun. I'm coding it in VHDL.

Anyway I'm stuck on the I2C communication with the MPU-6050. As bases I used the I2C master VHDL code from: https://www.digikey.com/eewiki/pages/viewpage.action?pageId=10125324.

I try to read the gyro registers and print them out on 8 leds just to see if I have some communication coming in.

I have tried to run with a 1Hz prescaler all the I2C phases in the state machine and light up some leds just to see if all phases are run through. This is the case. I have assigned the pins 2.5V default, I use 10k pull up resistors. The MPU6050 works perferct on an arduino.

    library ieee;
    use ieee.std_logic_1164.all;
    use ieee.numeric_std.all;

     entity mpu6050_2 is
    port( clk_50 : in std_logic;
            areset : in std_logic;  
            i2c_SDA : INOUT  STD_LOGIC;
            i2c_SCL : INOUT  STD_LOGIC;
            leds : out std_LOGIC_VECTOR(7 downto 0)
     );
     end entity mpu6050_2;

     architecture struc of mpu6050_2 is

     component i2c_master is
     GENERIC(
     input_clk : INTEGER := 50_000_000; 
     bus_clk   : INTEGER := 400_000);   
     PORT(
      clk       : IN     STD_LOGIC;                   
      reset_n   : IN     STD_LOGIC;                   
      ena       : IN     STD_LOGIC;                   
      addr      : IN     STD_LOGIC_VECTOR(6 DOWNTO 0); 
      rw        : IN     STD_LOGIC;                    
      data_wr   : IN     STD_LOGIC_VECTOR(7 DOWNTO 0);  
      busy      : OUT    STD_LOGIC;     
      data_rd   : OUT    STD_LOGIC_VECTOR(7 DOWNTO 0);
      ack_error : BUFFER STD_LOGIC;  
      sda       : INOUT  STD_LOGIC;                    
      scl       : INOUT  STD_LOGIC);       
      end component ;

      type machine is (config1, config2, gyroH, gyroL);
      signal state  : machine:= config1; --current state

      signal SDA_int : std_LOGIC;
      signal SCL_int : std_LOGIC;
      signal i2c_ena : std_LOGIC;
      signal i2c_busy : std_LOGIC;
      signal busy_prev : std_LOGIC;
      signal i2c_rw : std_LOGIC;
      signal i2c_data_wr : STD_LOGIC_VECTOR(7 DOWNTO 0);
      signal gyro_data : std_LOGIC_VECTOR(15 downto 0);
      signal i2c_data_rd : std_LOGIC_VECTOR (7 downto 0);
      signal i2c_addr : STD_LOGIC_VECTOR(6 DOWNTO 0);


begin

process(areset, clk_50) 

    VARIABLE busy_cnt  : INTEGER := 0;  --keeps track of i2c busy signals during transaction

    begin

    if areset = '0' then
        busy_cnt := 0; 
        i2c_ena <= '0';
        state <= config1;

    elsif rising_edge(clk_50) then

        case state is

        when config1 =>
            busy_prev <= i2c_busy;
            if (busy_prev = '0' and i2c_busy = '1') then
                busy_cnt := busy_cnt + 1;
            end if;

                case busy_cnt is
                    when 0 =>
                        i2c_ena <= '1';
                        i2c_addr <= "1101000"; --MPU6050 adress
                        i2c_rw <= '0'; --write
                        i2c_data_wr <= x"6B"; -- hex6B powermanagement          
                    when 1 =>
                        i2c_rw <= '0'; --write
                        i2c_data_wr <= "00000000"; -- ON with internal clock
                    when 2 =>
                            i2c_ena <= '0';
                            if(i2c_busy = '0') then
                                busy_cnt := 0;
                                state <= config2;
                            end if;

                    when others => NULL;
                end case;       

        when config2 =>
            busy_prev <= i2c_busy;
            if (busy_prev = '0' and i2c_busy = '1') then
                busy_cnt := busy_cnt + 1;
            end if;

                case busy_cnt is
                    when 0 =>
                        i2c_ena <= '1';
                        i2c_addr <= "1101000"; --MPU6050 adress
                        i2c_rw <= '0'; --write
                        i2c_data_wr <= x"1B"; -- Gyro config            
                    when 1 =>
                        i2c_rw <= '0'; --write
                        i2c_data_wr <= "00000000"; -- 250 degree/sec, no self test
                    when 2 =>
                            i2c_ena <= '0';
                            if(i2c_busy = '0') then
                                busy_cnt := 0;
                                state <= gyroH;
                            end if;
                    when others => NULL;
                end case;               


        when gyroH =>
            busy_prev <= i2c_busy;
            if (busy_prev = '0' and i2c_busy = '1') then
                busy_cnt := busy_cnt + 1;
            end if;

                case busy_cnt is
                    when 0 =>
                        i2c_ena <= '1';
                        i2c_addr <= "1101000"; --MPU6050 adress
                        i2c_rw <= '0'; --write
                        i2c_data_wr <= x"43"; -- hex43 GYRO_OUT[15:8]           
                    when 1 =>
                        i2c_rw <= '1'; --read
                    when 2 =>
                            i2c_ena <= '0';
                        if(i2c_busy = '0') then
                            gyro_data(15 downto 8) <= i2c_data_rd;
                            busy_cnt := 0;
                            state <= gyroL;
                        end if;
                    when others => NULL;
                end case;

        when gyroL =>   
            busy_prev <= i2c_busy;
            if (busy_prev = '0' and i2c_busy = '1') then
                busy_cnt := busy_cnt + 1;
            end if;

                case busy_cnt is
                    when 0 =>
                        i2c_ena <= '1';
                        i2c_addr <= "1101000"; --MPU6050 adress
                        i2c_rw <= '0'; --write
                        i2c_data_wr <= x"44"; -- hex44 GYRO_OUT[7:0]            
                    when 1 =>
                        i2c_rw <= '1'; --read
                    when 2 =>
                            i2c_ena <= '0';
                        if(i2c_busy = '0') then
                            gyro_data(7 downto 0) <= i2c_data_rd;
                            busy_cnt := 0;
                            state <= gyroH; 
                        end if;

                    when others => NULL;
                end case;           

        end case;
    end if;

end process;

u0: i2c_master
port map(clk => clk_50, reset_n => areset, ena => i2c_ena, addr => i2c_addr, rw => i2c_rw, data_wr => i2c_data_wr, busy => i2c_busy, data_rd => i2c_data_rd
, sda => SDA_int, scl => SCL_int);

leds(7) <= gyro_data(0); --D4 
leds(6) <= gyro_data(1); -- D5 
leds(5) <= gyro_data(4); -- D6 
leds(4) <= gyro_data(7); -- D7 
leds(3) <= gyro_data(8);  -- D8 
leds(2) <= gyro_data(11); -- D9
leds(1) <= gyro_data(13); -- D10
leds(0) <= gyro_data(15); -- D11

i2c_SDA <= SDA_int;
i2c_SCL <= SCL_int;


end struc;

Result: all the leds dont change status despite if i rotate the MPU6050. So no communication. Can anyone help me what i'm doing wrong?

Answer 1

First: I'm using the same component in one of my designs and do confirm it works.

I think you are just using the wrong i2c address to begin with.

In datasheets, i2c addresses are usually given including the read/write bit (for the MPU-6050, this is 0x68/01101000 and 0x69/01101001). The i2c master component used, however, expects to build the final i2c address by itself by appending (&) the i2c rw bit to the given address (see line 124 in the original sources), thus you must pass the address from the datasheet shifted by one bit.

Try using 0x34/0110100 as i2c address for read and write instead.

I only looked very briefly into the rest of your code (so there might be other culprits as well), but this should be enough to get you going.