Diff: pwm.c

Revision:

0:cb80470434eb

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pwm.c	Tue Oct 28 12:19:42 2014 +0000
@@ -0,0 +1,49 @@
+/*
+Copyright 2013 Paul Soulsby www.soulsbysynths.com
+    This file is part of Atmegatron.
+
+    Atmegatron is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    Atmegatron is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Atmegatron.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+//*****Pulse Width Modulation.  This sets a portion of the waveform to 0.   The amount of the waveform blanked is set by the LFO and LFO amount******
+
+#include "atmegatron.h"
+
+//lets and gets
+byte pwm_lfoamt = 0;                
+//LFO amount  - stored as byte 0-31.  represents the maximum proportion of waveform that can be blanked.  
+void PWM_Let_LFOAmt(byte newamt)
+{
+  pwm_lfoamt = newamt;
+}
+
+
+byte PWM_Get_LFOAmt(void)
+{
+  return pwm_lfoamt;
+}
+
+//PWM meat
+void PWM_Process(void)
+{
+  byte i;
+  long curindex, maxindex;
+  if (pwm_lfoamt > 0) {                                                                        //pwm on:
+    maxindex = (WAVE_LEN - pwm_lfoamt);                                                        //intermediate value - min possible index to start blanking
+    curindex = ((127 - LFO_Get_Level()) * (long)pwm_lfoamt * 8225 >> 21) + maxindex;           //then multiply by lfo level (8225 >> 21 is a way of doing / 255, without using a slow divide)
+    for(i=curindex;i<WAVE_LEN;i++){                                                            //blank the relevant part of the waveform
+      Wave_Let_Process(i, 0);
+    }
+  }
+}