Hello everyone, I am attempting to create an embedded device for a school project where I need to send some text data over USB on power-up. It is a constant stream of serial data.
For this, I am setting my own application as the entry point instead of NSH,
which requires me to instantiate the USB
output myself.
I have copied the USB console setup from NSH into my application, and I can see
the USB device showing up with `dmesg`
so I know it is successfully started. However, none of my `write()` calls to
the file descriptor or `fprintf` calls are
working correctly.
The code for the USB setup is:
```c
void board_late_initialize(void) {
/* Initialize the USB serial driver */
struct boardioc_usbdev_ctrl_s ctrl;
FAR void *handle;
int ret;
#if defined(CONFIG_CDCACM)
ctrl.usbdev = BOARDIOC_USBDEV_CDCACM;
ctrl.action = BOARDIOC_USBDEV_CONNECT;
ctrl.instance = 0;
ctrl.handle = &handle;
ret = boardctl(BOARDIOC_USBDEV_CONTROL, (uintptr_t)&ctrl);
UNUSED(ret); /* Eliminate warning if not used */
DEBUGASSERT(ret == OK);
#endif
}
```
Then I am writing to the USB device like so:
```c
#define USB_CONSOLE "/dev/ttyACM0"
do {
console = open(USB_CONSOLE, O_RDWR);
/* ENOTCONN means that the USB device is not yet connected, so sleep.
* Anything else is bad.
*/
DEBUGASSERT(errno == ENOTCONN);
sleep(1);
} while (console < 0);
/* Make USB stdout, stderr, stdin */
dup2(console, 0);
dup2(console, 1);
dup2(console, 2);
printf("A=%lf,B=%lf,G=%lf\n", pos.x, pos.y, pos.z);
```
I have tried using `fprintf` on the file descriptor returned by `open`, and
also using `write` directly to no avail. The
console just stays blank on my host computer.
Any ideas what else I could try?
Thanks,
Matteo
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