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[on:]

It appears that something SPI.end() changes isn't being reset by SPI.begin() on the Due. As a result, if SPI.end() is used to disable SPI, it can't be re-enabled later in the program. A simplified example is shown below.

This sequence works:

Code:

SPI.begin();
SPI.transfer(0);

This sequence hangs on the Due, but works on other Arduino boards:

Code:

SPI.end();
SPI.begin();
SPI.transfer(0);

[Reply #1 on:]

I can confirm this. (The problem seems to be that SPI.end() calls SPI_Disable(), but SPI.begin doesn't call SPI_Enable() - it's called in the constructor.)

To fix this: open the file hardware/arduino/sam/libraries/SPI/SPI.cpp and at the beginning of the SPIClass::begin() method add the line
SPI_Enable(spi);
The method should now look like this:

Code:

void SPIClass::begin() {
        SPI_Enable(spi);
        // NPCS control is left to the user

        // Default speed set to 4Mhz
        setClockDivider(BOARD_SPI_DEFAULT_SS, 21);
        setDataMode(BOARD_SPI_DEFAULT_SS, SPI_MODE0);
        setBitOrder(BOARD_SPI_DEFAULT_SS, MSBFIRST);
}

I've added this issue to the Arduino github here: https://github.com/arduino/Arduino/issues/1406

[Reply #2 on:]

Thanks. That fixes the problem. Is there somewhere else I should be posting this to make sure this fix gets into the SPI release version?

[Reply #3 on:]

I've already reported the issue in the official place and as it's a simple one-liner I expect it will get fixed pretty soon.