From 8cb19e052e288d6ebaa4280929d5b50d3d377271 Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@proton.me>
Date: Thu, 4 Jan 2024 15:28:54 +0100
Subject: [PATCH] fix: make sure scl changed after delay

---
 src/i2c/scl_generator.vhd   |  6 ++----
 tb/i2c/scl_generator_tb.vhd | 25 +++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/i2c/scl_generator.vhd b/src/i2c/scl_generator.vhd
index 0554ba2..0414306 100644
--- a/src/i2c/scl_generator.vhd
+++ b/src/i2c/scl_generator.vhd
@@ -30,7 +30,6 @@ architecture a1 of scl_generator is
   signal can_change : std_logic;
 
   signal req_change : std_logic;
-  signal change : std_logic;
 
   signal scl_changing : std_logic;
 
@@ -52,14 +51,13 @@ begin  -- architecture a1
   can_change <= '1' when curr_stable_count = MIN_STABLE_CYCLES else '0';
 
   -- requests a change of the SCL, not of SCL enable
-  req_change <= can_change and should_change;
-  change <= req_change and (scl_i xor exp_scl);
+  req_change <= '1' when (can_change and should_change) = '1' and next_stable_count /= 0 else '0';
 
   exp_scl <= '1' when should_rise = '1' and req_change = '1' else
              '0' when should_fall = '1' and req_change = '1' else
              not curr_scl_enable;
 
-  next_scl_enable <= curr_scl_enable xor change;
+  next_scl_enable <= not exp_scl;
 
   scl_changing <= scl_rising_i or scl_falling_i;
 
diff --git a/tb/i2c/scl_generator_tb.vhd b/tb/i2c/scl_generator_tb.vhd
index d638795..92fb950 100644
--- a/tb/i2c/scl_generator_tb.vhd
+++ b/tb/i2c/scl_generator_tb.vhd
@@ -134,6 +134,27 @@ begin  -- architecture tb
           for i in 0 to 10 loop
             check_equal(scl, 'H');
           end loop;  -- i
+        elsif run("continuous_rising") then
+          req_continuous;
+          for i in 0 to 5 loop
+            wait_delay(DELAY - 1);
+            report "Hi" & std_logic'image(scl);
+          end loop;  -- i
+
+          check_equal(scl, '0');
+          req_rising;
+          wait_delay(DELAY);
+          check_equal(scl, 'H');
+        elsif run("continuous_falling") then
+          req_continuous;
+          for i in 0 to 6 loop
+            wait_delay(DELAY - 1);
+          end loop;  -- i
+
+          check_equal(scl, 'H');
+          req_falling;
+          wait_delay(DELAY);
+          check_equal(scl, '0');
         elsif run("rising_scl_low") then
           scl <= '0'; -- pull down
           req_rising;
@@ -151,6 +172,8 @@ begin  -- architecture tb
           wait_delay(DELAY);
           check_equal(cannot_comply, '1');
           check_equal(scl_enable, '0');
+          wait_delay(DELAY);
+          check_equal(scl_enable, '0');
         end if;
     end loop;
 
@@ -161,6 +184,7 @@ begin  -- architecture tb
   begin  -- process scl_rising
     wait until rising_edge(scl);
     scl_rising <= '1';
+    wait until rising_edge(clk);
     wait until falling_edge(clk);
     scl_rising <= '0';
   end process set_scl_rising;
@@ -169,6 +193,7 @@ begin  -- architecture tb
   begin  -- process scl_rising
     wait until falling_edge(scl);
     scl_falling <= '1';
+    wait until rising_edge(clk);
     wait until falling_edge(clk);
     scl_falling <= '0';
   end process set_scl_falling;
-- 
2.48.1