cam: Add a way to check if a frame is ready without blocking

Author: jepler

ports/esp32s2/cam.c

@@ -372,6 +372,13 @@ size_t cam_take(uint8_t **buffer_p) {
     return frame_buffer_event.len;
 }
 
+bool cam_ready(void) {
+    frame_buffer_event_t frame_buffer_event;
+    BaseType_t result = xQueuePeek(cam_obj->frame_buffer_queue, (void *)&frame_buffer_event, 0);
+    return result != pdFALSE;
+}
+
+
 void cam_give(uint8_t *buffer) {
     if (buffer == cam_obj->frame1_buffer) {
         cam_obj->frame1_buffer_en = 1;

ports/esp32s2/cam.h

@@ -66,6 +66,13 @@ void cam_stop(void);
  */
 size_t cam_take(uint8_t **buffer_p);
 
+/**
+ * @brief Check whether a frame is available
+ *
+ * @return - true if cam_take() will complete immediately, false if it will block
+ */
+bool cam_ready(void);
+
 /**
  * @brief enable frame buffer to get the next frame data.
  *