3 files changed, 11 insertions(+), 3 deletions(-)

M src/i2c/slave.vhd
M src/i2c/tx.vhd
M tb/i2c/tx_tb.vhd

@@ 156,6 156,9 @@ begin  -- architecture a1
       scl_stretch_o         => tx_scl_stretch,
       sda_i                 => sda_i,
       sda_enable_o          => tx_sda_enable,
+      unexpected_sda_o      => open,    -- ignore in the slave, nothing to do?
+                                        -- TODO output an error if unexpected
+                                        -- level when transmitting
       ready_o               => tx_ready_o,
       valid_i               => tx_valid_i,
       write_data_i          => tx_data_i);

@@ 24,10 24,11 @@ entity tx is
     clk_i               : in  std_logic;
     rst_in              : in  std_logic;
     start_write_i       : in  std_logic;
-    ss_condition_i      : in std_logic;    -- Reset rx circuitry
-    clear_buffer_i      : in std_logic;
+    ss_condition_i      : in  std_logic;    -- Reset rx circuitry
+    clear_buffer_i      : in  std_logic;
 
-    expect_ack_i        : in std_logic;
+    expect_ack_i        : in  std_logic;
+    unexpected_sda_o    : out std_logic;
     err_noack_o         : out std_logic;
 
     scl_rising_pulse_i  : in  std_logic;


@@ 80,6 81,7 @@ begin  -- architecture a1
   scl_stretch_o <= '1' when curr_state = WAITING_FOR_DATA else '0';
   ready_o <= ready and not curr_err_noack;
   sda_enable_o <= not tx_buffer(8) when curr_state = SENDING else '0';
+  unexpected_sda_o <= '1' when curr_state = SENDING and sda_i /= tx_buffer(8) else '0';
   err_noack_o <= curr_err_noack;
 
   ready <= '0' when curr_tx_buffers_filled(curr_saving_buffer_index) = '1' or curr_err_noack = '1' else '1';

@@ 29,6 29,8 @@ architecture a1 of tx_tb is
   signal write_data : std_logic_vector(7 downto 0);
   signal scl_stretch : std_logic;
 
+  signal unexpected_sda : std_logic;
+
   signal err_noack : std_logic;
 
   signal validate_sda_stable_when_scl_high : std_logic := '0';


@@ 133,6 135,7 @@ begin  -- architecture a1
       scl_stretch_o         => scl_stretch,
       scl_rising_pulse_i    => scl_rising_pulse,
       scl_falling_delayed_i => scl_falling_pulse,
+      unexpected_sda_o      => unexpected_sda,
       sda_enable_o          => sda_enable,
       sda_i                 => sda,
       ready_o               => ready,