From efbdb48966a7676d0f3158f89f5fe9205e6c333a Mon Sep 17 00:00:00 2001
From: Selene ToyKeeper
Date: Mon, 16 Aug 2021 04:56:54 -0600
Subject: made dynamic PWM phase-correct; replaced brute-force phase reset to
 avoid flickering (I didn't see any flickering on my lights, but SammysHP
 reported it was visible)

---
 spaghetti-monster/fsm-ramping.c | 41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

(limited to 'spaghetti-monster/fsm-ramping.c')

diff --git a/spaghetti-monster/fsm-ramping.c b/spaghetti-monster/fsm-ramping.c
index 503f90f..1a08149 100644
--- a/spaghetti-monster/fsm-ramping.c
+++ b/spaghetti-monster/fsm-ramping.c
@@ -153,30 +153,33 @@ void set_level(uint8_t level) {
         #endif  // ifdef USE_TINT_RAMPING
 
         #ifdef USE_DYN_PWM
+            uint16_t top = PWM_GET(pwm_tops, level);
+            #ifdef PWM1_CNT
+            // wait to ensure compare match won't be missed
+            // (causes visible flickering when missed, because the counter
+            //  goes all the way to 65535 before returning)
+            // (see attiny1634 reference manual page 103 for a warning about
+            //  the timing of changing the TOP value (section 12.8.4))
+            // to be safe, allow at least 64 cycles to update TOP
+            while(PWM1_CNT > (top - 64)) {}
+            #endif
             // pulse frequency modulation, a.k.a. dynamic PWM
-            PWM1_TOP = PWM_GET(pwm_tops, level);
+            PWM1_TOP = top;
+
+            // repeat for other channels if necessary
             #ifdef PMW2_TOP
-            PWM2_TOP = PWM_GET(pwm_tops, level);
+                #ifdef PWM2_CNT
+                while(PWM2_CNT > (top - 64)) {}
+                #endif
+                PWM2_TOP = top;
             #endif
             #ifdef PMW3_TOP
-            PWM3_TOP = PWM_GET(pwm_tops, level);
-            #endif
-
-            // reset the phase, to avoid random long pulses
-            // see attiny1634 reference manual page 103 for a warning about
-            // the timing of changing the TOP value (section 12.8.4)
-            // (we don't care about being phase-correct, so the brute-force
-            //  approach can be used to reset it here)
-            #ifdef PWM1_CNT
-            PWM1_CNT = 0;
-            #endif
-            #ifdef PWM2_CNT
-            PWM2_CNT = 0;
-            #endif
-            #ifdef PWM3_CNT
-            PWM3_CNT = 0;
+                #ifdef PWM3_CNT
+                while(PWM3_CNT > (top - 64)) {}
+                #endif
+                PWM3_TOP = top;
             #endif
-        #endif
+        #endif  // ifdef USE_DYN_PWM
     }
     #endif  // ifdef OVERRIDE_SET_LEVEL
     #ifdef USE_DYNAMIC_UNDERCLOCKING
-- 
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