Timer Capture DMA

Horea Aflat

Other Parts Discussed in Thread: EK-TM4C1294XL

Good day,

I have a small problem regarding reading data for timer capture using DMA on the board EK-TM4C1294XL.
According with "TivaWar Peripheral Driver Library" spmu298a.pdf the procedure to initialize the DMA is:

+uDMAEnable() is called once to enable the controller.
+uDMAControlBaseSet() is called once to set the channel control table.
+uDMAChannelAttributeEnable() is called once or infrequently to configure the behavior of the
channel.
+uDMAChannelControlSet() is used to set up characteristics of the data transfer. It is only called
once if the nature of the data transfer does not change.
+uDMAChannelTransferSet() is used to set the buffer pointers and size for a transfer. It is called
before each new transfer.
+uDMAChannelEnable() enables a channel to perform data transfers.
+uDMAChannelRequest() is used

I attached a test project which reads DMA at a timer capture interrupt time.
Can you please take a look and send me an answer what I did wrong.
timer_capture_dma.zip

Regards
Horea

over 10 years ago

0 Amit Ashara over 10 years ago

TI__Guru**** 244440 points

Hello Horea

I think your code is missing the enable of the control trigger.

TimerControlTrigger(TIMER3_BASE, TIMER_A, true);

EDIT: The above was the case for ADC triggers. Can you please provide a snapshot of the Timer Registers when the condition is satisfied for the interrupt and dma event.

Regards
Amot

0 Horea Aflat over 10 years ago in reply to Amit Ashara

Intellectual 280 points

Amit,

Here is the picture:

Thanks

Horea

0 Amit Ashara over 10 years ago in reply to Horea Aflat

TI__Guru**** 244440 points

Hello Horea

The Timer A is not enabled in TIMERCTL register. Look at the value 0xC. The bit 0 which Timer A Enable is 0.

Regards
Amit

0 Horea Aflat over 10 years ago in reply to Amit Ashara

Intellectual 280 points

Hi Amit,

I am working at API level with C functions, like document: "TivaWare Peripheral Driver Library" (spmu298a.pdf).
The chapter 32. uDMA Controller lists all the C functions for DMA.
My question is: how I can translate your condition into an API function?

Thanks
Horea

0 Amit Ashara over 10 years ago in reply to Horea Aflat

TI__Guru**** 244440 points

Hello Horea,

Does the Timer Interrupt get asserted for capture count?

Regards
Amit

0 Horea Aflat over 10 years ago in reply to Amit Ashara

Intellectual 280 points

Hi Amit,

Yes, the interrupt is triggered for capture count.

Thanks
Horea

0 Horea Aflat over 10 years ago in reply to Horea Aflat

Intellectual 280 points

Hi Amit,

I improved my test project.

But it still not working.

I attached the project.

0876.timer_capture_dma.zip

Thanks

Horea

0 Amit Ashara over 10 years ago in reply to Horea Aflat

TI__Guru**** 244440 points

Hello Horea,

It will take me some time to get a setup working with the capture mode.

Regards
Amit

0 Amit Ashara over 10 years ago in reply to Horea Aflat

TI__Guru**** 244440 points

Hello Horea,

In the latest project file, there was an issue. When the timer match is reached the Timer is disabled. The user must re enable it.

extern "C" void hwiTimer3AFxn(void)
{
TimerIntClear(TIMER3_BASE, TIMER_CAPA_MATCH);
TimerEnable(TIMER3_BASE, TIMER_A);

Swi_post(swiTimer3A);
}

Also i moved the following configuration of the DMA to the main code.

// primary transfer set
uDMAChannelTransferSet(UDMA_CH2_TIMER3A | UDMA_PRI_SELECT,
UDMA_MODE_BASIC, // linear filling
(void *)(TIMER3_BASE + TIMER_O_TAV), // GPIOD data register
uiDest, // my buffer
sizeof(uiDest)); // buffer size

uDMAChannelEnable(UDMA_SEC_CHANNEL_TMR3A);

After that I see that for every timer interrupt I get one DMA transfer.

Regards
Amit

0 Horea Aflat over 10 years ago in reply to Amit Ashara

Intellectual 280 points

Hi Amit,

Thank you for your answer.

I attached the project updated.

Regards

Horea

2475.timer_capture_dma.zip

0 Amit Ashara over 10 years ago in reply to Horea Aflat

TI__Guru**** 244440 points

Hello Horea

So is it working or not working?

Regards
Amit

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Timer Capture DMA