Electronic – arduino – SPI Interrupt (SPIE) in SPI control register

arduinomicrocontrollerspistm32

I have been trying to understand SPI Interrupt i.e. what does it do and why is it used ? Reading about it on the web has not helped me. Can some one please explain it in a simple terms ?

Best Answer

SPIE or "SPI Interrupt Enable" is used to enable the interrupt.

(Assuming you are in Master mode) There are two ways of transferring data using SPI:

1.Polling: Here you write data in SPI's data register (SPDR) and then poll on the flag for SPI Transmission complete (SPIF).

2.Interrupt based: In this case, when you enable Interrupt for SPI, you write data in SPDR. Controller will transmit the data and will raise an interrupt when transmission is completed.

A question may arise that why there is interrupt for transmission but not for the reception, I am tempted to answer but It would be better if you figure that out! :-)

Related Solutions

Spi interrupt code

With SPI the master generates the clock so there's not really a concept of being able to receive multiple bytes back from a slave automatically, you have to send additional dummy bytes to generate the clock. Say if you had a sensor and you wanted command 0x01 to send back the current temperature the pseudo-code for the master may look like:

spi_write(0x01);
t_lsb = spi_write(0x00); // These dummy bytes are just needed to generate a clock
t_msb = spi_write(0x00); // So that the slave gets a chance to send the results back

On and the slave it might look like:

cmd = spi_read();
if (cmd == 0x01) {
  spi_write(t_lsb);
  spi_write(t_msb);
}

You can technically send back a byte from the slave for each byte sent from the master, but for most protocols there probably isn't anything useful to send back until the slave has received and decoded the command. Hopefully you can understand that pseudo-code and the general concept OK, it's been a while since I've programmed PIC SPI at the register level but it sounds like you're on top of that side of things.

Electronic – SPI communication – bits per second vs Hz

SPI is a fully synchronous serial protocol. For every clock cycle one bit is transferred.

There is, therefore. a 1:1 relationship between bits per second and hertz.

A 20MHz SPI bus runs at 20Mbps.

Best Answer

Related Solutions

Spi interrupt code

Electronic – SPI communication – bits per second vs Hz

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