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TM4C1290NCPDT: Advanced Bi-SSI Function with uDMA

INGS
Prodigy 120 points

Hi 
Here again trying to make it work bi-mode with udma the main problem is when i work without udma it work well but with udma always i got just have of the word .. 
normally to read in bi-mode i was doing:

SSIDataPut(SSI2_BASE, 0x00);
data = HWREG(SSI2_BASE + SSI_O_DR);

it was working perfect but with udma;

uDMAChannelTransferSet(UDMA_CH12_SSI2RX | UDMA_PRI_SELECT, UDMA_MODE_BASIC, (void *) (SSI2_BASE + SSI_O_DR), data,48);
uDMAChannelEnable(UDMA_CH12_SSI2RX);

for me it look like with udma still reading as legacy mode .. but usually i "write" to be able to read when i work without udma .. but with udma i dont "write" is it correct ? 
I am missing some configuration to make udma read in mode bi-mode.

  • 0
    TI__Guru 72500 points

    No, as a master you still need to do a "write" to generate the clocks for the read. In SSI_ADV_MODE_BI_READ mode, the write to the TX FIFO only generates clocks for the slave. To read data from the slave using only uDMA you need to setup two uDMA channels, one to write to the SSIDR and one to read from that register.