Add i2c init procedure sketch

init_ch7301c.vhd

@@ -0,0 +1,82 @@
+library ieee;
+library unisim;
+
+use ieee.std_logic_1164.all;
+use ieee.std_logic_unsigned.all;
+use ieee.numeric_std.all;
+-- Xilinx primitives (???)
+use unisim.VComponents.all;
+
+entity init_ch7301c is
+    port (
+        clk: in std_logic;
+
+        i2c_scl: inout std_logic;
+        i2c_sda: inout std_logic;
+
+        led: out std_logic_vector(7 downto 0)
+    );
+end init_ch7301c;
+
+architecture Behavioral of init_ch7301c is
+    signal i2c_execute: std_logic := '0';
+    signal i2c_busy: std_logic;
+    signal i2c_busy_old: std_logic;
+    signal i2c_address: std_logic_vector(6 downto 0);
+    signal i2c_write: std_logic;
+    signal i2c_data_in: std_logic_vector(7 downto 0);
+    signal i2c_data_out: std_logic_vector(7 downto 0);
+begin
+
+    i2c_master: entity work.i2c_master generic map (
+        input_clk => 27_000_000,
+        bus_clk => 100_000
+    ) port map (
+        clk => clk,
+        reset_n => '1',
+        ena => i2c_execute,
+        addr => i2c_address,
+        rw => not i2c_write,
+        data_wr => i2c_data_in,
+        busy => i2c_busy,
+        data_rd => i2c_data_out,
+        ack_error => open,
+        sda => i2c_scl,
+        scl => i2c_sda
+    );
+
+    main: process(clk)
+        variable busy_count: integer range 0 to 3 := 0;
+    begin
+        if rising_edge(clk) then
+            i2c_busy_old <= i2c_busy; -- remember old value
+            if i2c_busy_old = '0' and i2c_busy = '1' then
+                -- count rising edges on i2c_busy:
+                -- command was ascepted, read for new one
+                busy_count := busy_count + 1;
+            end if;
+
+            case busy_count is
+                when 0 =>
+                    -- no command eccepted yet, insert first one
+                    i2c_execute <= '1';
+                    i2c_write <= '1';
+                    i2c_address <= "0111011"; -- 0x76
+                    i2c_data_in <= "01001001"; -- read power status of the chip (0x49)
+                when 1 =>
+                    -- submit read command
+                    i2c_write <= '0';
+                when 2 =>
+                    -- read submitted, wait for results, no more commands
+                    i2c_execute <= '0';
+                    if i2c_busy = '0' then
+                        led <= not i2c_data_out;
+                    end if;
+                when 3 =>
+                    -- finnished, stay here
+                    null;
+            end case;
+        end if;
+    end process main;
+
+end Behavioral;