Re: [Xenomai-help] error on rt_dev_read, code Success, what does it mean?

[Jan Kiszka <jan.kiszka@domain.hid>]

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Everett Wang wrote:
> On Sat, Jun 12, 2010 at 6:45 PM, Jan Kiszka <jan.kiszka@domain.hid> wrote:
>> Everett Wang wrote:
>>> Thanks. I looked my code again, which is modified from example
>>> cross-link.c. The section looks like:
>>>
>>> ...
>>>                  irq_time = rx_event.rxpend_timestamp;
>>>                 read = rt_dev_read(read_fd, &write_time, sz);
>>>                 if (read == sz) {
>>>                         read_time = rt_timer_read();
>>>                         printf("%3d |%16llu |%16llu |%16llu\n", nr,
>>>                                irq_time  - write_time,
>>>                                read_time - irq_time,
>>>                                read_time - write_time);
>>>                         nr++;
>>>                 } else if (read < 0 ) {
>>>                         printf(RTASK_PREFIX "error on rt_dev_read, code %s\n",
>>>                                strerror(-err)); <<<<<<<===========
>>>                         break;
>>>                 } else {
>>>                         printf(RTASK_PREFIX "only %d / %d byte received \n",
>>>                                read, sz);
>>>                         break;
>>>                 }
>>> ...
>>> I guess I should change the strerror(-err) to strerror(-read).
>> Indeed, the example suffers from some copy&paste mistakes. Same for the
>> write path. And closing in a loop is no longer required. A cleanup is
>> needed.
>>
>>> If I do
>>> that, I some
>>> times get a " code input/output error". That is better. What can cause
>>> input/output error?
>> Try RTSER_RTIOC_GET_STATUS to learn more.
> 
> Thanks for answer my questions, I added
> 
> err = rt_dev_ioctl(gps_fd,
>                         RTSER_RTIOC_GET_STATUS, &serstatus);
> printf(STASK_PREFIX "Error code line_status=%d
> modem_status=%d\n",serstatus.line_status, serstatus.modem_status);
> 
> This prints a message:
> 
> gps_task: Error code line_status=98 modem_status=187
> 
> Line_status bits are  RTSER_LSR_TRANSM_EMPTY , RTSER_LSR_THR_EMTPY,
> RTSER_LSR_OVERRUN_ER
> 
> and modem status bits:
>  RTSER_MSR_DCD, 	RTSER_MSR_DSR ,RTSER_MSR_CTS, 	RTSER_MSR_DDCD,
> RTSER_MSR_DDS, RTSER_MSR_DCTS
> 
> Does it caused by "RTSER_LSR_OVERRUN_ER"?
> The GPS device outputs upto 450 characters every 0.1 second.

Looking at your code, you probably want to clear the quickly overflowing
RX queue and pending overflow errors before entering the read loop.

Jan


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