change DEBUG optimization option from O0 to Og

add uart write to board test example

examples/device/board_test/src/main.c

@@ -42,6 +42,8 @@ enum  {
   BLINK_UNPRESSED = 1000
 };
 
+#define HELLO_STR   "Hello from TinyUSB\n"
+
 int main(void)
 {
   board_init();
@@ -49,13 +51,20 @@ int main(void)
   uint32_t start_ms = 0;
   bool led_state = false;
 
+
   while (1)
   {
     uint32_t interval_ms = board_button_read() ? BLINK_PRESSED : BLINK_UNPRESSED;
 
+    // uart echo
+//    uint8_t ch;
+//    if ( board_uart_read(&ch, 1) ) board_uart_write(&ch, 1);
+
     // Blink every interval ms
     if ( !(board_millis() - start_ms < interval_ms) )
     {
+      board_uart_write(HELLO_STR, strlen(HELLO_STR));
+
       start_ms = board_millis();
 
       board_led_write(led_state);

examples/make.mk

@@ -79,7 +79,7 @@ CFLAGS += \
 
 # Debugging/Optimization
 ifeq ($(DEBUG), 1)
-  CFLAGS += -O0 -ggdb -DCFG_TUSB_DEBUG=1
+  CFLAGS += -Og -ggdb -DCFG_TUSB_DEBUG=2
 else
 ifneq ($(BOARD), spresense)
   CFLAGS += -flto -Os