pico: use a low priority alarm for audio when core1 is disabled

32blit · Sep 26, 2023 · d8b3c10 · d8b3c10
1 parent f487e36
commit d8b3c10
Showing 1 changed file with 17 additions and 3 deletions.
diff --git a/32blit-pico/main.cpp b/32blit-pico/main.cpp
@@ -2,6 +2,7 @@
 
 #include "hardware/structs/rosc.h"
 #include "hardware/vreg.h"
+#include "hardware/timer.h"
 #include "pico/binary_info.h"
 #include "pico/multicore.h"
 #include "pico/rand.h"
@@ -104,6 +105,7 @@ void update(uint32_t);
 
 bool core1_started = false;
 
+#ifdef ENABLE_CORE1
 void core1_main() {
   core1_started = true;
   multicore_lockout_victim_init();
@@ -118,6 +120,15 @@ void core1_main() {
   }
 }
 
+#else
+static void alarm_callback(uint alarm_num) {
+  update_audio(::now());
+
+  timer_hw->intr = 1 << alarm_num;
+  hardware_alarm_set_target(alarm_num, make_timeout_time_ms(5));
+}
+#endif
+
 int main() {
 #if OVERCLOCK_250
   // Apply a modest overvolt, default is 1.10v.
@@ -193,6 +204,12 @@ int main() {
 
 #if defined(ENABLE_CORE1)
   multicore_launch_core1(core1_main);
+#else
+  // fallback audio timer if core1 is unavailable / not enabled
+  int alarm_num = hardware_alarm_claim_unused(true);
+  hardware_alarm_set_callback(alarm_num, alarm_callback);
+  hardware_alarm_set_target(alarm_num, make_timeout_time_ms(5));
+  irq_set_priority(TIMER_IRQ_0 + alarm_num, PICO_LOWEST_IRQ_PRIORITY);
 #endif
 
   blit::set_screen_mode(ScreenMode::lores);
@@ -208,9 +225,6 @@ int main() {
     update_display(now);
     update_input();
     int ms_to_next_update = tick(::now());
-#if !defined(ENABLE_CORE1)
-    update_audio(now);
-#endif
     update_led();
     update_usb();
     update_multiplayer();