[En-Nut-Discussion] Ethernut with CAN-IF

[Huett W.]

Thanks, for the information. I will try it, and for sure have much fun with
ethernut.
Perhaps you can answer one more question.
Should the mode pin of sja1000 selected for Intel or Motorola ?

Best regards

Wolfgang Hütt
----- Original Message -----
From: "Ole Reinhardt" <ole.reinhardt at kernelconcepts.de>
To: "Ethernut User Chat (English)" <en-nut-discussion at egnite.de>
Sent: Wednesday, July 27, 2005 12:29 PM
Subject: Re: [En-Nut-Discussion] Ethernut with CAN-IF


> Hello,
>
> > I'm searching for some information how the ethernut could be extended
with a new CAN device.
> > I've seen already some sources sja1000.c etc. with a complete set of HW
Driver functions.
> > How is this connected with Nut/OS ? (Same as already existing devices
NutRegister,NUTDEVICE......)
>
> I have added CAN support for SJA1000 devices. Especialy I have made
> these extensions having our own CAN board in mind.
>
> http://www.kernelconcepts.de/products/mcan/
>
> In detail you can use the SJA1000 driver like a "normal" device driver.
>
> Initialisation phase:
>
> u_short base_address = 0x8000;
> NutRegisterDevice(&devSJA1000, base_address, 0);
>
> The base address can be passed as parameter of NutRegisterDevice.
> The interrupt can not be passed, but specified in include files (see
> include/cfg/m-can.h). I don't use the configurator as it is not running
> on my system, but it should be possible to set the interrupt in the
> configurator as well.
>
> Configuration example:
>
> #define SJA_SIGNAL     sig_INTERRUPT7
> #define SJA_EICR       EICRB
> #define SJA_SIGNAL_BIT 7
>
> After initialisation you can use the functions defined in
> include/dev/can_dev.h
>
> These functions can transmit only raw frames. A frame is defined as:
>
> struct _CANFRAME {              // todo: Implement flags
>     u_long id;                  // Identifier
>     u_char len;                 // Length of frame, max = 8
>     u_char byte[8];
>     u_char ext;                 // Boolean, extendet frame
>     u_char rtr;                 // Boolean, remote transmition bit
> };
>
> The functions you can use are:
>
> Setting an acceptance filter and acceptance mask:
>
> void   CAN_SetFilter(NUTDEVICE *dev, u_char *ac, u_char *am);
>
> For more information about this filter take a look into the sja1000
> datasheet.
>
>
> Transmit a frame (blocking):
>
> void   CAN_TxFrame(NUTDEVICE *dev, CANFRAME *frame);
>
> Try to transmit a frame:
>
> u_char CAN_TryTxFrame(NUTDEVICE *dev, CANFRAME *frame);
>
> On success this returns 0, if there is no free transmit buffer 1.
>
> u_char CAN_TxFree(NUTDEVICE *dev);
>
> This returns the space available in the transmit buffer.
>
>
> Same for the receiving functions:
>
> void   CAN_RxFrame(NUTDEVICE *dev, CANFRAME *frame);
> u_char CAN_TryRxFrame(NUTDEVICE *dev, CANFRAME *frame);
> u_char CAN_RxAvail(NUTDEVICE *dev);
>
> An example receive code could look like this:
>
>
> while (!CAN_TryRxFrame(&devSJA1000, &frame))
> {
>     if (count == MAX_DEVICES) {
>         error = ERR_TOO_MUCH_DEVICES;
>         break;
>     }
>     if ((frame.rtr) || (!frame.ext)) {
>         error = ERR_INVALID_FRAME;
>     } else {
>         source_id = (u_char) frame.id;
>         dest_id = (u_char) (frame.id >> 8);
>         cmd = (u_char) (frame.id >> 16);
> ...
>
> An example send code could look like this:
>
> void SendCANFrame(u_char prio, u_char source, u_char dest, u_char cmd,
> u_char length, can_msg_t * message)
> {
>     CANFRAME frame;
>     frame.id = ((u_long) (prio & 0x07) << 26) | ((u_long) cmd << 16) |
> ((u_long) dest << 8) | ((u_long) source);
>     frame.len = length;
>     frame.ext = 1;
>     frame.rtr = 0;
>     memcpy(frame.byte, message, length);
>     CAN_TxFrame(&devSJA1000, &frame);
> }
>
> Hope this helps... If you need help with your application feel free to
> contact us.
>
> Best regards,
>
> Ole Reinhardt
>
> --
> kernel concepts    Tel: +49-271-771091-14
> Dreisbachstr. 24   Fax: +49-271-771091-19
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> --
>
>
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