change blink to use PICO_DEFAULT_LED_PIN to support other boards (#57)

* change blink to use PICO_DEFAULT_LED_PIN to support other boards

* also update pio/pwm and picoboard/blinky system/hello_double_tap

Author: hathach

blink/blink.c

@@ -7,7 +7,7 @@
 #include "pico/stdlib.h"
 
 int main() {
-    const uint LED_PIN = 25;
+    const uint LED_PIN = PICO_DEFAULT_LED_PIN;
     gpio_init(LED_PIN);
     gpio_set_dir(LED_PIN, GPIO_OUT);
     while (true) {

picoboard/blinky/blinky.c

@@ -8,7 +8,7 @@
 #include "pico/stdlib.h"
 #include "hardware/gpio.h"
 
-const uint LED_PIN = 25;
+const uint LED_PIN = PICO_DEFAULT_LED_PIN;
 const uint DOT_PERIOD_MS = 100;
 
 const char *morse_letters[] = {

pio/pwm/pwm.c

@@ -33,7 +33,7 @@ int main() {
     uint offset = pio_add_program(pio, &pwm_program);
     printf("Loaded program at %d\n", offset);
 
-    pwm_program_init(pio, sm, offset, 25);
+    pwm_program_init(pio, sm, offset, PICO_DEFAULT_LED_PIN);
     pio_pwm_set_period(pio, sm, (1u << 16) - 1);
 
     int level = 0;