RTOS/TM4C1294NCPDT: SPI DMA Ping Pong Mode

I know of no inherent reason why you cannot use uDMA in Ping-Pong mode for both the TX and RX data.

Hi,

I have configured SPI Tx and Rx for Ping pong mode and its working fine.

My question is,
1. Can I use Circular buffer in Basic mode to send data continuously?
2. Without reconfiguring the buffer in DMA ISR? can I transfer data continuously through SPI TX ?



Regards,
Manohar.

1. Use Ping-Pong mode for continuous transfers. Basic mode stops after the count expires and does not reset the buffer address.
2. Yes, using Ping-Pong mode.

Hi,

I am transferring a 2048 bytes of data to my DMA SPI Rx, which is configured in ping pong mode with each buffer size to be 512bytes.
How to make a continuous transfer? because after the completion of pong buffer, the channel is disabling.

Because of this, only 1024 bytes of data is send at a time. After that I have to enable the channel to continue receiving.


Question:
1. Is there is any way I can receive data continuously without the channel is disabling after pong buffer?
2.Maximum of 1024 bytes are received in ping pong buffer with a size of 512 each? why?


Regards,
Manohar

Hi,

Below is the code:

void ISRhandler()
{
//check primary Rx channel
ulMode = uDMAChannelModeGet(UDMA_CHANNEL_SSI0RX | UDMA_PRI_SELECT);
if(ulMode == UDMA_MODE_STOP) {

memcpy(ui8ReceivedBuf, ui8DMAPrimary_Buffer, SSI_RXBUF_SIZE);
uDMAChannelTransferSet(UDMA_CHANNEL_SSI0RX | UDMA_PRI_SELECT,
UDMA_MODE_PINGPONG, (void *)(SSI0_BASE + SSI_O_DR),
ui8DMAPrimary_Buffer, SSI_RXBUF_SIZE);
}


//check Alternate Rx channel
ulMode = uDMAChannelModeGet(UDMA_CHANNEL_SSI0RX | UDMA_ALT_SELECT);
if(ulMode == UDMA_MODE_STOP) {

memcpy(ui8ReceivedBuf, ui8DMASecondary_Buffer, SSI_RXBUF_SIZE);
uDMAChannelTransferSet(UDMA_CHANNEL_SSI0RX | UDMA_ALT_SELECT,
UDMA_MODE_PINGPONG, (void *)(SSI0_BASE + SSI_O_DR),
ui8DMASecondary_Buffer, SSI_RXBUF_SIZE);


}
event_post();
}

buffer size is 64 bytes each ping and pong, the mode is working fine and if I send data below 128 bytes as of ping and pong buffer the event is posted for 2 times. if I send above 128 bytes the event post is still 2 times only and the channel is getting disabled after pong buffer? why?

I can re- enable the channel again in ISR, but the transfer is not continuous.



Regards,
Manohar

The Ping-Pong mode does require the CPU to process the data and reconfigure the Channel Control Word once the transfers to or from one buffer has completed. Since the DMA has now switched to the second buffer, the transfers continue without stopping.