hello_double_tap: use pico_bootsel_via_double_reset from SDK

Author: Wren6991

system/CMakeLists.txt

@@ -1,5 +1,4 @@
 if (NOT PICO_NO_HARDWARE)
-    add_subdirectory(double_tap_usb_boot)
     add_subdirectory(narrow_io_write)
     add_subdirectory(hello_double_tap)
     add_subdirectory(unique_board_id)

system/double_tap_usb_boot/CMakeLists.txt

@@ -2,12 +2,19 @@ add_executable(hello_double_tap
         hello_double_tap.c
         )
 
-# Double tap reset into bootrom is injected by linking with the double_tap_usb_boot library
+# Double tap reset into bootrom is injected by linking with the
+# pico_bootsel_via_double_reset library
 target_link_libraries(hello_double_tap
         pico_stdlib
-        double_tap_usb_boot
+        pico_bootsel_via_double_reset
         )
 
+# Entering the bootloader in this way also lets us specify a GPIO to be used
+# as a bootloader activity LED:
+target_compile_definitions(hello_double_tap PRIVATE
+	PICO_BOOTSEL_VIA_DOUBLE_RESET_ACTIVITY_LED=25
+	)
+
 pico_add_extra_outputs(hello_double_tap)
 
 # add url via pico_set_program_url

system/double_tap_usb_boot/double_tap_usb_boot.c

@@ -6,10 +6,14 @@
 
 #include "pico/stdlib.h"
 
-// This is a regular old LED blinking example, however it is linked with double_tap_usb_boot
-// so pressing reset quickly twice, will reset into USB bootloader
+// This is a regular old LED blinking example, however it is linked with the
+// `pico_bootsel_via_double_reset` library, so resetting the board twice
+// quickly will enter the USB bootloader. This is useful for boards which have
+// a reset button but no BOOTSEL, as long as you remember to always link the
+// `pico_bootsel_via_double_reset` library!
+
 int main() {
-    const uint LED_PIN = 21;
+    const uint LED_PIN = PICO_DEFAULT_LED_PIN;
     gpio_init(LED_PIN);
     gpio_set_dir(LED_PIN, GPIO_OUT);
     while (true) {