Prevent custom task blocking tud_task for 5s every time

Author: will-v-pi

usb/device/dev_multi_cdc/main.c

@@ -9,9 +9,15 @@
 #include <tusb.h>
 
 #include <pico/stdio.h>
+#include <pico/stdlib.h>
 
 void custom_cdc_task(void);
 
+bool tud_task_callback(__unused struct repeating_timer *t) {
+    tud_task();
+    return true;
+}
+
 int main(void)
 {
     // Initialize TinyUSB stack
@@ -26,15 +32,18 @@ int main(void)
     // let pico sdk use the first cdc interface for std io
     stdio_init_all();
 
+    // TinyUSB device task must be called regularly, so we use a repeating timer
+    struct repeating_timer timer;
+    add_repeating_timer_ms(1, tud_task_callback, NULL, &timer);
+
     // main run loop
     while (1) {
-        // TinyUSB device task | must be called regurlarly
-        tud_task();
-        
-        // custom tasks
+        // custom tasks can run in the main loop without blocking the TinyUSB task
         custom_cdc_task();
     }
 
+    cancel_repeating_timer(&timer);
+
     // indicate no error
     return 0;
 }

usb/device/dev_multi_cdc/usb_descriptors.c

@@ -15,7 +15,7 @@
 #define CDC_EXAMPLE_VID     0xCafe
 // use _PID_MAP to generate unique PID for each interface
 #define CDC_EXAMPLE_PID     (0x4000 | _PID_MAP(CDC, 0))
-// set USB 2.0
+// set to 2.10 so the MS_OS_20_DESCRIPTOR works
 #define CDC_EXAMPLE_BCD     0x0210
 
 // String descriptors referenced with .i... in the descriptor tables