LPC54102 Software Trigger DMA

[rhsalced]

Hello,

My goal is start/stop DMA transfers via software control. From the main loop I would like to start/stop DMA transfers.

The version of the SDK that I am using is v.3.04.000 and the example project is spis_dma. The reason for using this version is that I am working with legacy code that expects this version of the SDK. I am not planning on using the latest SDK and do not plan to.

From my understanding, I need to configure the DMA to be software trigger driven. From the UM10850 14.7.1 doc:

• “CFGVALID and SV allows a more direct DMA block timing control by software”
  1. Are these set in the .xfercfg on lines 131, 138, 146, 153 or should they be set elsewhere?

• ”Leaving a CFGVALID bit set to 0 allows the DMA sequence to pause at the description unit software triggers the continuation”
  1. How and where do I set this up?

• “If a channel is configured with SWTRIG = 0, the channel can be later triggered either by hardware or software. Software triggering is accomplished by writing a 1 to the appropriate bit in the SETTRIG register”
  1. How and where do I set this register from the main loop?

• “When a channel is initially set up, the SWTRIG bit in the XFERCFG register can be set, causing the transfer to begin immediately”

I am unsure if I am configuring the DMA to be software driven.

 Also, I don’t know what function/register I should call to start/stop the transfer. I’m calling the Chip_DMA_SetTrigChannel() function from the main loop, I don’t think I’m using this function correctly.

All that I am trying to do is set a DMA transfer once a second from the main loop via a software trigger. I could really use some help on how to do this.

The changes that I made to spis_dma.c

• Set SPI as master
  1. Original project SPI was configured as slave. Set spiSetup.master = 1 on line 80.
• Removed DMA_XFERCFG_RELOAD from xfercfg (lines 131, 138, 146, 153). I think I needed to do this so the DMA wouldn’t continuously execute.
• Commented out spis_dma_Start(); from lines 189 and line 201.
• In main, calling software dma trigger once a second. Lines 257- 258.

Any help on how to set up a software DMA trigger would be appreciated.

Thanks!