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SEM_ipost() problem

Started by lwj ●July 10, 2004
I am working with the c6712 and I am having problems with semaphores. We
are using one of the McBSPs to implement a UART. Our code is based on
the TI Sample code. In my transmit code I am trying to use a semaphore
to block the task during the EDMA transfer:

void SerialTransmit(char *Bytes, int Count)
{
while (Count)
{
//Wait for any EDMA transfer in progress.
SEM_pend(TxSema, SYS_FOREVER);
SendCount = MIN(Count, EDMA_BUFFER_MAX);
//Configure EDMA and fill the buffer.
FillEdmaBuffer(Bytes, SendCount);
//Kick-off the EDMA transfer.
KickOffEdmaTransfer();
//Update the buffer info.
Bytes += SendCount;
Count -= SendCount;
}
} The relevant parts of the transfer complete ISR are void TransferCompleteISR(void)
{
EDMA_intClear();
EDMA_disableChannle();

//Signal any waiting tasks that the transfer is complete
SEM_ipost(TxSema);
} The problem is that the SEM_ipost() does not seem to change the
semaphore count. Because the count does not change my code blocks on the
SEM_pend....

I googled around a bit and saw some references to wrapping the ISR code
with HWI_disable() and HWI_enable()/HWI_restore() but this does not
change the problem.

I created the semaphore with CCS.

The count is initialized to 1.

The first call to SEM_pend does not seem to change the count either!
However, the second time it does. I am looking at the semaphore value
using the object view in CCS.

Does anyone have any ideas on what I might be doing wrong?

Thanks.



Reply by Brett Olsen ●July 12, 20042004-07-12
Hi.

I am sucessfully using the SEM_ipost within the context of an ISR, but I believe that you must be using the HWI dispatcher in order for this to be sucessful.
I have not used any HWI_disable or HWI_enable calls either.

Goodluck,
Brett

lwj wrote:
I am working with the c6712 and I am having problems with semaphores.
We
are using one of the McBSPs to implement a UART. Our code is based on
the TI Sample code. In my transmit code I am trying to use a semaphore
to block the task during the EDMA transfer:
void SerialTransmit(char *Bytes, int Count)
{
while (Count)
{
//Wait for any EDMA transfer in progress.
SEM_pend(TxSema, SYS_FOREVER);
SendCount = MIN(Count, EDMA_BUFFER_MAX);
//Configure EDMA and fill the buffer.
FillEdmaBuffer(Bytes, SendCount);
//Kick-off the EDMA transfer.
KickOffEdmaTransfer();
//Update the buffer info.
Bytes += SendCount;
Count -= SendCount;
}
}
The relevant parts of the transfer complete ISR are
void TransferCompleteISR(void)
{
EDMA_intClear();
EDMA_disableChannle();
//Signal any waiting tasks that the transfer is complete
SEM_ipost(TxSema);
}
The problem is that the SEM_ipost() does not seem to change the
semaphore count. Because the count does not change my code blocks on the
SEM_pend....
I googled around a bit and saw some references to wrapping the ISR code
with HWI_disable() and HWI_enable()/HWI_restore() but this does not
change the problem.
I created the semaphore with CCS.
The count is initialized to 1.
The first call to SEM_pend does not seem to change the count either!
However, the second time it does. I am looking at the semaphore value
using the object view in CCS.
Does anyone have any ideas on what I might be doing wrong?
Thanks.
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Brett Olsen
Senior DSP Design Engineer
Tait Electronics Ltd
535 Wairakei Rd
Christchurch
New Zealand
 
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