From e811d778ea51ac1e25588a9cc957fca4f532ea5a Mon Sep 17 00:00:00 2001
From: Brett Weiland <brett_weiland@bpcspace.com>
Date: Fri, 27 Oct 2023 07:10:26 -0500
Subject: init

---
 software_pwm.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 software_pwm.c

(limited to 'software_pwm.c')

diff --git a/software_pwm.c b/software_pwm.c
new file mode 100644
index 0000000..561edfd
--- /dev/null
+++ b/software_pwm.c
@@ -0,0 +1,89 @@
+#include <stdint.h>
+#include <string.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <stdbool.h>
+#include <stddef.h>
+
+#include "software_pwm.h"
+#include "pins.h"
+
+
+static struct link_pair {
+  struct pwm_event *next; 
+  struct pwm_event *prev;
+};
+
+//if next is ever zero, node is assumed not part of list/disabled
+static struct pwm_event {
+  struct link_pair active;
+  struct link_pair twins;
+  uint8_t time;
+  uint8_t pins;
+  bool enabled;
+} events[SOFTPWM_PIN_COUNT + 1];
+
+
+#define LIST_INSERT(new, former, member) (\
+    list_insert(&(new.member), &(former.member), offsetof(struct pwm_event, time)))
+
+static void list_insert(struct link_pair *new_links, struct link_pair *former_links, size_t parent_offset) {
+
+}
+
+static void list_remove(struct link_pair *event) {
+}
+
+void init_softpwm() {
+
+  //this one never moves
+  events[SOFTPWM_PIN_COUNT].time = 0;
+  events[SOFTPWM_PIN_COUNT].pins = 0;
+  events[SOFTPWM_PIN_COUNT].active.next = &events[SOFTPWM_PIN_COUNT];
+  events[SOFTPWM_PIN_COUNT].active.prev = &events[SOFTPWM_PIN_COUNT];
+  events[SOFTPWM_PIN_COUNT].enabled = true;
+
+  //TODO: move all to zero once init_softpwm tested
+  for(size_t event_i = 0; event_i < SOFTPWM_PIN_COUNT; event_i++) {
+    events[event_i].time = event_i;
+    events[event_i].pins = (1 << (event_i + 1)) - 1;
+    LIST_INSERT(events[event_i], events[((int)event_i - 1) % (SOFTPWM_PIN_COUNT + 1)], active);
+  }
+
+  SOFTPWM_DDR = 0xff; 
+
+  //use external 10mhz clock (we just have one laying around)
+  //then prescale by 1024. Check at different freqs for brightness
+  TCCR0A = 0b00000010;
+  TIMSK0 = 0b00000011;
+  OCR0A = events[SOFTPWM_PIN_COUNT].time;
+  TIFR0 = 0b00000010; //interupts enabled!
+  sei();
+}
+
+void softpwm_set(uint8_t pin, uint8_t duty) { 
+  /**
+  struct pwm_event *event_unmoved = &events[pin]; //TODO describe if you want ig
+  struct pwm_event *this_event = &events[pin];
+  this_event->time = duty;
+  if(duty < events[pin].time) {
+    while(duty < event_unmoved->time) event_unmoved = event_unmoved->next;
+  }
+  else {
+  }
+  **/
+}
+
+/**
+ISR(TIMER0_OVF_vect) {
+}
+**/
+
+ISR(TIMER0_COMP_vect) {
+  /**
+  static struct pwm_event *on_event = &events[SOFTPWM_PIN_COUNT];
+  SOFTPWM_PORT = on_event->pins;
+  on_event = on_event->next;
+  OCR0A = on_event->time;
+  **/
+}
-- 
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