Not Finding devices and warnings on Arduino M0 about arduino

[jpliew]

@DiE-MaRMeLaDe due to differences in 32bit SAMD21 in M0 and 8bit 32U4 using int, you may be able to cast (uint8_t) in line 150 and 151 of WebUSB.cpp

D_ENDPOINT((uint8_t)USB_ENDPOINT_OUT(pluggedEndpoint),USB_ENDPOINT_TYPE_BULK,0x40,0),
D_ENDPOINT((uint8_t)USB_ENDPOINT_IN (pluggedEndpoint+1),USB_ENDPOINT_TYPE_BULK,0x40,0)

This will remove the -Wnarrowing error. However there should more error that was missed

C:\Users\JP\Documents\Arduino\libraries\WebUSB\WebUSB.cpp:164:42: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]

    if (USB_SendControl(0, &landingPage, 1) < 0)

It will be really hard to get rid of this without major reworking on the M0 USBCore.cpp

uint32_t USBDeviceClass::sendControl(const void* _data, uint32_t len)
{
	const uint8_t *data = reinterpret_cast<const uint8_t *>(_data);
	uint32_t length = len;
	uint32_t sent = 0;
	uint32_t pos = 0;

	if (_dry_run == true)
		return length;

	if (_pack_message == true) {
		memcpy(&_pack_buffer[_pack_size], data, len);
		_pack_size += len;
		return length;
	}

 	while (len > 0)
 	{
		sent = armSend(EP0, data + pos, len);
		pos += sent;
		len -= sent;
 	}

	return length;
}

Above, you can see that in SAMD21's USBCore.cpp the command sendControl only returns unsigned number but in Leonardo sendControl has negative 1 number return that mean something

int USB_SendControl(u8 flags, const void* d, int len)
{
	int sent = len;
	const u8* data = (const u8*)d;
	bool pgm = flags & TRANSFER_PGM;
	while (len--)
	{
		u8 c = pgm ? pgm_read_byte(data++) : *data++;
		if (!SendControl(c))
			return -1;
	}
	return sent;
}

So, either you report a bug at Arduino M0's github or it will be easier and less stress to use another board that is listed here, since M0 is a retired product.

Hope this helps. If you think this answer your questions, please close this issue.