Continuous SPI Interrupts

charles saperstein

Using an F28335. I copied the code from the Example_28335Spi_FFDLB_int sample. Only thing I did differently is to turn off internal loopback and set it to 8 bits instead of 16 bits. With nothing connected to the SPI on my device, I am getting constant Rx and Tx interrupts.

What's up with that?

over 10 years ago

0 charles saperstein over 10 years ago

Expert 1445 points

P.S. I'm using SCI interrupts and receiving data.

0 Mark Labbato over 10 years ago in reply to charles saperstein

Guru 30330 points

Charles,

Can you elaborate on the issue you are having? The code in the example will continuously send and receive data. Even if you disable the Internal loopback and leave the SPI pins unconnected, the RX interrupt will still fire. It is based on the number of SPICLKs received. In master mode, the SPI will always send and receive data with every word transmitted. If you do not wish to receive any data, you can just disable the SPIRX interrupt.

-Mark

0 charles saperstein over 10 years ago in reply to Mark Labbato

Expert 1445 points

I guess my question is that we never do a Tx in the main(), so what causes the Tx interrupt to get fired in the first place?

0 Mark Labbato over 10 years ago in reply to charles saperstein

Guru 30330 points

The TX interrupt will fire because you enabled the Interrupt in the module and at the CPU level, and there are 0 words in the transmit FIFO. The TX interrupt will fire until TXFFST is greater than TXFFIL. If you do not want these interrupts to constantly fire, you can dynamically enable/disable the interrupt in the PIE until they are needed. If you do not ever want TX interrupts, do not enable them in the module.

Regards,
Mark

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Continuous SPI Interrupts