shithub: m8c

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Improve cpu usage

- Makes nonblocking calls to serial read
- Moves main thread wait to an SDL_Delay() call
- Adds an INI parameter to control SDL_Delay() argument/ thread sleep time

This is not a perfect solution but lower end and battery powered systems may
get a lot of mileage out of it. On higher-end systems with large thread wakeup
periods, there may be an impact to framerate, limiting it below 60.

--- a/config.c

+++ b/config.c

@@ -23,6 +23,7 @@

   c.init_fullscreen = 0;  // default fullscreen state at load

   c.init_use_gpu = 1;     // default to use hardware acceleration

+  c.idle_ms = 10;         // default to high performance

   c.key_up = SDL_SCANCODE_UP;

   c.key_left = SDL_SCANCODE_LEFT;

@@ -78,6 +79,7 @@

           conf->init_fullscreen ? "true" : "false");

   sprintf(ini_values[initPointer++], "use_gpu=%s\n",

           conf->init_use_gpu ? "true" : "false");

+  sprintf(ini_values[initPointer++], "idle_ms=%d\n", conf->idle_ms);

   sprintf(ini_values[initPointer++], "[keyboard]\n");

   sprintf(ini_values[initPointer++], "key_up=%d\n", conf->key_up);

   sprintf(ini_values[initPointer++], "key_left=%d\n", conf->key_left);

@@ -164,6 +166,7 @@

 void read_graphics_config(ini_t *ini, config_params_s *conf) {

   const char *param_fs = ini_get(ini, "graphics", "fullscreen");

   const char *param_gpu = ini_get(ini, "graphics", "use_gpu");

+  const char *idle_ms = ini_get(ini, "graphics", "idle_ms");

   if (strcmpci(param_fs, "true") == 0) {

     conf->init_fullscreen = 1;

@@ -176,6 +179,9 @@

     } else

       conf->init_use_gpu = 0;

   }

+

+  if (idle_ms)

+    conf->idle_ms = SDL_atoi(idle_ms);

 }

--- a/config.h

+++ b/config.h

@@ -10,6 +10,7 @@

   char *filename;

   int init_fullscreen;

   int init_use_gpu;

+  int idle_ms;

   int key_up;

   int key_left;

--- a/main.c

+++ b/main.c

@@ -35,6 +35,8 @@

   // TODO: take cli parameter to override default configfile location

   read_config(&conf);

+  SDL_Log("idle_ms=%d", conf.idle_ms);

+

   // allocate memory for serial buffer

   uint8_t *serial_buf = malloc(serial_read_size);

@@ -115,7 +117,8 @@

     while (1) {

       // read serial port

-      int bytes_read = sp_blocking_read(port, serial_buf, serial_read_size, 1);

+      //int bytes_read = sp_blocking_read(port, serial_buf, serial_read_size, 1);

+      int bytes_read = sp_nonblocking_read(port, serial_buf, serial_read_size);

       if (bytes_read < 0) {

         SDL_LogCritical(SDL_LOG_CATEGORY_ERROR, "Error %d reading serial. \n",

                         (int)bytes_read);

@@ -140,6 +143,7 @@

       }

     }

     render_screen();

+    SDL_Delay(conf.idle_ms);

   }

   // exit, clean up

--- a/render.c

+++ b/render.c

@@ -203,7 +203,7 @@

 }

 void render_screen() {

-  if (dirty && (SDL_GetTicks() - ticks > 14)) {

+  if (dirty) {

     dirty = 0;

     ticks = SDL_GetTicks();

     SDL_SetRenderTarget(rend, NULL);

-- 

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