A bit of a hack, here is what I do.
I usually put a static variable in the CDC file called usb_configured and
initialize it to 0. When cdcacm_set_config is called, I set it to one.
Then my main loop calls pop char, looks like this:
static void pop_usb_char(void)
{
if (!usb_configured)
return;
if (!qempty(cdc->tx.head, cdc->tx.tail)) {
if (usbd_ep_write_packet(iface, 0x82,
&cdc->tx.buf[cdc->tx.tail], 1) == 0) {
return;
}
cdc->tx.tail = qinc(cdc->tx.tail, cdc->queuesize);
}
}
Works well, but wont work if the device is self powered, and you disconnect the
usb and plug it back in.
Hope that helps.
Sincerely,
Jason
> On Nov 9, 2015, at 11:41 AM, Matthew Lai <[email protected]> wrote:
>
> Cool! That demo code does do that.
>
> I am not sure if it is completely compliant however.
>
> It implements SET_LINE_CODING and SET_CONTROL_LINE_STATE, but the
> capability bit (0x2) indicates that we support GET_LINE_CODING as well.
> The bit indicates support for these 3 requests (and a notification,
> which we don't care about).
>
> There is no way to indicate support for only SET_CONTROL_LINE_STATE.
>
> And it seems like the only symbol missing (for implementing this) in
> cdc.h is GET_LINE_CODING.
>
> I am not sure if GET_LINE_CODING is actually ever sent by Windows or
> Linux, and whether not supporting it (despite setting the capability
> bit) would actually be a problem.
>
> Thanks
> Matthew
>
> On 2015-11-09 4:41 AM, Karl Palsson wrote:
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> Hrm, I thought the ti/lm4f cdc-acm demo code did this, but it
>> might have it locally. The definitions from the standard would be
>> certainly welcome in cdc.h
>>
>> Cheers,
>> Karl P
>>
>> Matthew Lai <[email protected]> wrote:
>>> Upon further research, I found that there is an optional "Set
>>> Control Line State" request that does exactly what I want. It
>>> is not yet implemented in cdc.h.
>>>
>>> I am going to implement it myself unless someone has done it
>>> already?
>>>
>>> Thanks
>>> Matthew
>>>
>>> On 2015-11-08 11:31 PM, Matthew Lai wrote:
>>>> Hello!
>>>>
>>>> I am using CDC ACM as a debug logging interface, so sometimes there is a
>>>> USB cable connected, and sometimes there isn't.
>>>>
>>>> My send routine looks like this -
>>>>
>>>> int ret = 0;
>>>>
>>>> do
>>>> {
>>>> ret = usbd_ep_write_packet(usbd_dev, 0x82, data, size);
>>>> }
>>>> while (ret == 0);
>>>>
>>>> However, if I call this function when either the USB cable isn't plugged
>>>> in or serial monitor is not opened on the computer, usbd_ep_write_packet
>>>> will just keep returning 0.
>>>>
>>>> Is there a way around this? Is there a way to tell whether the function
>>>> returned zero because there is no receiver, or if it returned zero
>>>> because it's busy and we should retry? Detecting whether the cable is
>>>> plugged in (or even whether the device is enumerated) is insufficient.
>>>>
>>>> Thanks!
>>>> Matthew
>>>>
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>
>
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