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uDMA SPI doubt

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     Hi there, please bear with me, english is not my mother tongue, I have a doubt about  SPI reading through udma.
     In order to get the clock to perform a reading of spi via udma , Do I need to start a udma write  also in the TX channel, or as soon as I start the RX udma all the clocks are generated internaly without any further write. I mean, after the first write (dummy) which will start the receiving proccess??
     I hope i've made myself clear.

Thanks in advance


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What MCU are you using?



The SPI FIFOS can trigger the uDMA to make a transfer. Look at Table 9-1. μDMA Channel Assignments on the datasheet.

You can see that the RX FIFO and TX FIFO each have their own trigger source. So if you want the uDMA to take data from a array into the TX FIFO (to transmit), of the SSI0, you need to set up DMA channel 11 for that. If you want the uDMA to take data from the RX FIFO into a array, then you need to set up the DMA channel 10 (again, this considering your using SSI0, each TX/RX from each SSI module have their own DMA channel).

So you see, each FIFO has it's own trigger.


Also notice that the TX and RX have different setups since the TX sends data, so the ideia is array->TX FIFO, and RX FIFO->array.



In short, if you configure a TX FIFO to trigger the DMA, you need to do the same to the RX FIFO

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