converted noctigon-dm11-boost to use PWM+DSM, and recalibrated timing for delays + smooth steps

Anduril has gradually gotten faster over the years, apparently, so it
needed longer delays to get accurate-ish timing for beacon and other modes.
Adding DSM also changes the timing perceptibly, so I made it possible to
calibrate the delay fudge factor on a per-build basis.

1 files changed, 50 insertions, 13 deletions

diff --git a/hwdef-noctigon-dm11-boost.c b/hwdef-noctigon-dm11-boost.c
index 08e2798..932323a 100644
--- a/hwdef-noctigon-dm11-boost.c
+++ b/hwdef-noctigon-dm11-boost.c
@@ -1,11 +1,11 @@
 // Noctigon DM11 (boost driver) PWM helper functions
 // Copyright (C) 2023 Selene ToyKeeper
 // SPDX-License-Identifier: GPL-3.0-or-later
-
 #pragma once
 
 #include "chan-rgbaux.c"
 
+
 void set_level_zero();
 
 void set_level_main(uint8_t level);
@@ -22,6 +22,12 @@ Channel channels[] = {
 
 
 void set_level_zero() {
+    // disable timer overflow interrupt
+    // (helps improve button press handling from Off state)
+    DSM_INTCTRL &= ~DSM_OVF_bm;
+
+    // turn off all LEDs
+    ch1_dsm_lvl = 0;
     CH1_PWM = 0;
     PWM_CNT = 0;  // reset phase
     CH1_ENABLE_PORT  &= ~(1 << CH1_ENABLE_PIN );  // disable opamp
@@ -30,28 +36,59 @@ void set_level_zero() {
 
 // single set of LEDs with single power channel, boost
 void set_level_main(uint8_t level) {
-    CH1_ENABLE_PORT  |= (1 << CH1_ENABLE_PIN );  // enable opamp
-    CH1_ENABLE_PORT2 |= (1 << CH1_ENABLE_PIN2);  // enable PMIC
+    PWM_DATATYPE ch1 = PWM_GET(pwm1_levels, level);
 
-    PWM_DATATYPE ch1_pwm = PWM_GET(pwm1_levels, level);
-    // pulse frequency modulation, a.k.a. dynamic PWM
-    uint16_t top = PWM_GET16(pwm_tops, level);
+    // set delta-sigma soft levels
+    ch1_dsm_lvl = ch1;
+
+    // set hardware PWM levels and init dsm loop
+    CH1_PWM = ch1_pwm = ch1 >> 7;
+
+    // enable timer overflow interrupt so DSM can work
+    DSM_INTCTRL |= DSM_OVF_bm;
 
-    CH1_PWM = ch1_pwm;
-    // wait to sync the counter and avoid flashes
-    while(actual_level && (PWM_CNT > (top - 32))) {}
-    PWM_TOP = top;
     // force reset phase when turning on from zero
     // (because otherwise the initial response is inconsistent)
     if (! actual_level) PWM_CNT = 0;
+
+    CH1_ENABLE_PORT  |= (1 << CH1_ENABLE_PIN );  // enable opamp
+    CH1_ENABLE_PORT2 |= (1 << CH1_ENABLE_PIN2);  // enable PMIC
 }
 
+// delta-sigma modulation of PWM outputs
+// happens on each Timer overflow (every 512 cpu clock cycles)
+// uses 8-bit pwm w/ 7-bit dsm (0b 0PPP PPPP PDDD DDDD)
+ISR(DSM_vect) {
+    // set new hardware values first,
+    // for best timing (reduce effect of interrupt jitter)
+    CH1_PWM = ch1_pwm;
+
+    // calculate next values, now that timing matters less
+
+    // accumulate error
+    ch1_dsm += (ch1_dsm_lvl & 0x007f);
+    // next PWM = base PWM value + carry bit
+    ch1_pwm  = (ch1_dsm_lvl >> 7) + (ch1_dsm > 0x7f);
+    // clear carry bit
+    ch1_dsm &= 0x7f;
+}
+
+
 bool gradual_tick_main(uint8_t gt) {
-    PWM_DATATYPE pwm1 = PWM_GET(pwm1_levels, gt);
+    PWM_DATATYPE ch1 = PWM_GET(pwm1_levels, gt);
+
+    // adjust multiple times based on current brightness
+    // (so it adjusts faster/coarser when bright, slower/finer when dim)
+
+    // higher shift = slower/finer adjustments
+    const uint8_t shift = 9;  // ((255 << 7) >> 9) = 63 max
+    uint8_t steps;
 
-    GRADUAL_ADJUST_SIMPLE(pwm1, CH1_PWM);
+    steps = ch1_dsm_lvl >> shift;
+    for (uint8_t i=0; i<=steps; i++)
+        GRADUAL_ADJUST_SIMPLE(ch1, ch1_dsm_lvl);
 
-    if (   (pwm1 == CH1_PWM)
+    if ((ch1 == ch1_dsm_lvl)
        ) {
         return true;  // done
     }