TMS570LS3137: MIBSPI + DMA - First transaction all 0's

Hi Paul,

I am suspecting this issue is due to the below mentioned reason:

(+) TMS570LS3137: MibSPI Slave -> Master transfer 1st value missing first bit - Arm-based microcontrollers forum - Arm-based microcontrollers - TI E2E support forums

Could you please try the workaround i given in the above thread once?

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Thanks & regards,
Jagadish.

Hi Jagadish,

I tried that, but it didn't help.

It's the whole transaction that 0'd though, not just the first bit.

I really think it must be the first DMA does not occur, but then fine after that. I can't work out why the first DMA would be phantom. The source data is in uncached RAM, BTW.

On a possibly related note, the SPI doesn't work AT ALL unless I het the restart button in CCS.

i.e.

Hit debug in CCS --> sometime it pauses at main(), sometimes it just carries on.

Hit resume if paused -> IO lines are configured (clk goes low, MOSI goes low)

Nothing further changes on the lines

Hit suspend then restart --> goes back to main()

Hit resume --> SPI transactions as they should (apart from the first) 

Through all of this I have CAN packets output, and when suspend is hit, the processor will stop somewhere sensible.

No SPI either if I press the PORST or RESET buttons on the devkit

Some interesting findings...

Originally, I would set up the Rx/Tx g_dmaCTRL structures with defaults, but NOT call dmaSetCtrlPacket there on init.

instead I was completing the struct (setting src/dst, size etc) then calling dmaSetCtrlPacket just prior to mibspiEnableGroupNotification.

This caused the the symptoms described above.

Now, if I add dmaSetCtrlPacket after setting up the structs (so with incorrect src/dst etc) on initialisation, then setting the proper src/dst etc along with dmaSetCtrlPacket each transfer I DO get all the transfers from power-on, and the first transfer is not zeros... instead it's nonsense (so probably dereferencing the null pointer and sending that).

So I've been fiddling around, and still I've not found a way of having proper data in the first transfer.

Hi Paul,

I am providing you some references to MibSPI DMA in Hercules,

1. Here is the video tutorial:

Hercules Tutorial: MibSPI and DMA Overview - YouTube

2. Go through the HALCoGen Help Topics

Here you can find one more example with step by step procedure

3. (+) [FAQ] TMS570LS3137: TMS570LS3137 MibSPI5 Tx and Rx with DMA - Arm-based microcontrollers forum - Arm-based microcontrollers - TI E2E support forums

Try to verify all these examples and try to solve the issue at your end.

If none of them helpful to solve your issue, then if possible, share your code for quick debugging at my end.

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Thanks & regards,
Jagadish.

Hi Paul,

Paul Sheppard said:

OK, I think I found it.

It was enabling the DMA transfers (not starting them) too early.

Good to hear that paul.

Paul Sheppard said:

Still not quite there though. Still investigating...

Take your time and let me know if you need any further assistance.

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Thanks & regards,
Jagadish.