The problem of ATmega168's SPI sending register SPIF not being set-EEWORLD

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Use the ATmega168 hardware SPI driver 74HC595 to expand the serial interface. Set MOSI and SCK to output, and then set the registers. , as follows:

static void vSpi595Init(void)

{

DDRB|=(1<

DDRD|=(1<

SPCR=(1<

}

Then call the following send function

static void vSPIMasterTransmit(unsigned char ucData)

{

SS_L(); //Pull down the storage register clock

SPDR = ucData; // Start data transmission

while(!(SPSR & (1<

SS_H(); //Pull up the storage register clock

}

But I found that the SPIF interrupt was not generated. Replacing the chip, adjusting the clock and SPI rate did not work.

Later I searched on ouravr website and found that many people encountered the same problem, and someone gave a solution. It is necessary to set the SS pin to output.

The modified initialization function is

static void vSpi595Init(void)

{

DDRB|=(1<

DDRD|=(1<

SPCR=(1<

}

That is to say, when acting as a host, SS must be set to output, and after the chip is reset, the SS pin defaults to input, so it must be actively set in the program. It seems that this is not clearly stated in the datasheet.

Keywords：ATmega168 Reference address：The problem of ATmega168's SPI sending register SPIF not being set

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