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From: berde on 9 Jul 2008 08:57
Hi,

I'm using the IAR development kit, Olimex LPC2378-STK. I'm trying to run
the CAN demo Software. But it just keep hanging here : while ( !(CAN1GSR &
(1 << 3)) );
Does anyone know how to solve this problem?

May thanks,

From: Heinz-Jürgen Oertel on 10 Jul 2008 16:42
berde wrote:

> Hi,
>
> I'm using the IAR development kit, Olimex LPC2378-STK. I'm trying to run
> the CAN demo Software. But it just keep hanging here : while ( !(CAN1GSR &
> (1 << 3)) );
> Does anyone know how to solve this problem?
>
> May thanks,

Reading the C statement, I guess the condition is always true.
What is the bit 3 in register CAN1GSR telling us? Can you please look up the
manual of the NXP chip.


Heinz

From: Paul Keinanen on 11 Jul 2008 02:21
On Wed, 09 Jul 2008 07:57:47 -0500, "berde"
<joramboekhoudt(a)hotmail.com> wrote:

>Hi,
>
>I'm using the IAR development kit, Olimex LPC2378-STK. I'm trying to run
>the CAN demo Software. But it just keep hanging here : while ( !(CAN1GSR &
>(1 << 3)) );
>Does anyone know how to solve this problem?

I hope CAN1GSR is declared as volatile.

Otherwise, an optimizing compiler might just once test that bit and
if not set, go into an infinite loop.

Paul

From: Heinz-Jürgen Oertel on 12 Jul 2008 10:12
Paul Keinanen wrote:

> On Wed, 09 Jul 2008 07:57:47 -0500, "berde"
> <joramboekhoudt(a)hotmail.com> wrote:
>
>>Hi,
>>
>>I'm using the IAR development kit, Olimex LPC2378-STK. I'm trying to run
>>the CAN demo Software. But it just keep hanging here : while ( !(CAN1GSR &
>>(1 << 3)) );
>>Does anyone know how to solve this problem?
>
> I hope CAN1GSR is declared as volatile.
>
> Otherwise, an optimizing compiler might just once test that bit and
> if not set, go into an infinite loop.
>
> Paul

Register GSR is the "Global Controller Status and Error Counters"
Bit 3 contains "TCS[3] Transmit Complete Status".
The manual says:
0 (incomplete) - At least one requested transmission has not been
successfully completed yet.


I think that it can be that the transmission in his case does not finish.
One reason, the CAN transceiver gets no acknowledge. A typical failure of
novices. CAN is in this regard very different from sending a byte via a
UART.

But of course, declaring the register as volatile is good practice.

Heinz
From: Paul Keinanen on 12 Jul 2008 10:55
On Sat, 12 Jul 2008 16:12:53 +0200, Heinz-J�rgen Oertel
<hj.oertel(a)t-online.de> wrote:

>
>I think that it can be that the transmission in his case does not finish.
>One reason, the CAN transceiver gets no acknowledge. A typical failure of
>novices. CAN is in this regard very different from sending a byte via a
>UART.

This might well be the case, since the OP did not say anything about
what other devices there are on the bus.

If the development kit is the only device on the CAN bus, the
transmitter tries over and over again to send the same message, until
an other device is connected to the bus, which acknowledges the
transmission.

This CANbus feature can be quite nasty if you are sending commands
over CANbus and the bus is intermittent for some reason. When the bus
is finally working again, a very outdated command might get through,
causing various kinds of hazards. In such cases, some higher level
protocol is required, e.g heartbeat messages or time tagged commands
etc. Clearing the transmission queue and reseting the CAN controller
chip if it appears to be stuck also reduces the risk related to
delayed commands.

Paul

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