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SDK • HELLO_USB uses USB, but Blink ... Not

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Hi Sirs,

HELLO_USB uses USB, i.e., it sends the content of e.g. “printf(”Hello, world - %i !\n“, i++);” to the USB port.
I can then receive and read the output on my PC using any serial monitor (e.g., PuTTY or VS Code).
As a nice side effect, make / picotool can reset the PICO to boot mode if necessary.
HELLO_USB is not particularly difficult, so I was able to find the probably relevant line:

Code:

stdio_init_all();
and add them to Blink, what now looks like this

Code:

 int main() {       int rc = pico_led_init();    hard_assert(rc == PICO_OK);    stdio_init_all();    while (true) {        printf("Hello, world!\n");        pico_set_led(true);        sleep_ms(LED_DELAY_MS_ON);        pico_set_led(false);        sleep_ms(LED_DELAY_MS_OF);    }}
But: No effect. No COM port.
And consequently, of course, nothing to read.
To load a new program into PICO, press bootsel and unplug/plug into the USB.
Which isn't so great, as my PC USB ports informed me after the first 50 times.

However, why does PICO not open a USB connection to the PC in the case of “Blink,” but does so in the case of “Hello_USB”?

Cheers,
Martin

Statistics: Posted by MartinHill — Thu Jan 29, 2026 6:20 pm — Replies 3 — Views 42



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