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TM4C123GH6PM: 32-bit transaction via SPI with DMA in ping-pong/scatter-gather modes

Pavel Mychko
Intellectual 360 points
Part Number: TM4C123GH6PM

There are some discussions on the forum about 32-bit SPI transactions, but they are not suitable for me - I need continuous flow transfer through SPI (like I2S sound stream) with 32-bit data per one frame sync pulse. I tried a lot of variants but they didn't work. I can't use GPIO for control FS because CPU doesn't control SPI port - it's controlled by DMA.

I wonder if it possible at all or not?

  • 0
    TI__Guru 72500 points
    Unfortunately the TM4C123 family does not support the advanced modes of SSI that are found on the newer TM4C129 parts. Those parts support variable frame sizes in advanced mode.

    I have not tried it, but you might look into using Peripheral Scatter-Gather mode of the uDMA with the first task being to send out the 32 bits on the SSI and the next task to toggle a GPIO pin. If the resulting pulse on the GPIO pin is too short, you might change the second task to start a timer pin toggle or another SSI transmission to generate a pulse of the required width.