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Date: Tue, 17 Jun 2008 10:29:57 +0200
From: Wolfgang Grandegger <wg@domain.hid>
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Subject: Re: [Xenomai-help] Hello, doubts with RT-CAN
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To: quinty <webquinty2@domain.hid>
Cc: xenomai@xenomai.org

quinty wrote:
> 
> 
> 2008/6/17 Wolfgang Grandegger <wg@domain.hid 
> <mailto:wg@domain.hid>>:
> 
>     quinty wrote:
> 
>         Hello,
> 
>         I am testing RT-CAN with MPC5200 and linux 2.6.23.14
>         <http://2.6.23.14> <http://2.6.23.14> , xenomai 2.4.2.
>         <http://2.4.2.> <http://2.4.2.>
> 
>         Well I have some doubts:
>         1.- In kernel configuration, there is a parameter to change
>         lenght of RX CAN buffer, 1024 by default.
>         What units???, 1024 bytes, 1024 telegrams??'
> 
> 
>     It is in bytes and must be 2^n.
> 
> 
>         2.- RT-CAN is a block or non-block??? in other words, when I use
>         rtcanrecv examples, code wait in this line of code
> 
>         ret = rt_dev_recvfrom
>         <http://www.xenomai.org/documentation/branches/v2.4.x/html/api/group__userapi.html#g0cc144457c649f197d485581686273dd>(s,
>         (void *)&frame, sizeof(can_frame_t
>         <http://www.xenomai.org/documentation/branches/v2.4.x/html/api/structcan__frame.html>),
>         0,(struct sockaddr *)&addr, &addrlen);, until driver recieve
>          message.
> 
> 
>     Yes, unless you have opened the socket with the non-blocking flag.
> 
> 
> 
>         3.- Have RT-CAN TX buffer???
> 
> 
>     No, Out-going messages are not queued.
> 
>     What is your problem?
> 
>     Wolfgang.
> 
> Hello Wolfgang,
> 
> well, in this moment I have not clear what is my problem. I have made 
> some examples with my board to try understand rt-can.
> 
> About non-block
> 
> ret = rt_dev_recvfrom(can_fd, (void *)&frame, sizeof(can_frame_t), 
> *MSG_DONTWAIT*,
>             (struct sockaddr *)&addr, &addrlen);
> 
> I have used this flag to not wait a message, but now, you told me that I 
> must open the socket with the non-blocking flag.

I'm wrong and your are right.

> 
> can_fd = rt_dev_socket(PF_CAN, SOCK_RAW, CAN_RAW);
> ret = rt_dev_ioctl(can_fd, SIOCGIFINDEX, &ifr);
> 
> but in this lines, I do not known how to set non-blocking flag.

See above.

> I am going to explaind you my problem. I am connected a device with CAN. 
> This device send message every 5ms with differents ID, for example, 
> 0x136, 0x624, 0x664, etc etc, then I need to read this telegrams and the 
> same time, I must calculate some values to send and check other process. 
> If driver is block, I can not check other process.

You could use a multi-threaded application with proper synchronization. 
But your single-threaded approach is a valuable option as well.

Wolfgang.