What steps will reproduce the problem?
1. Use a library that has SPI access inside an ISR.
2. Run the "Webserver" Ethernet example.
3. Trigger the SPI interrupt on second device while webserver is running.
What is the expected output? What do you see instead?
The system hangs. The SPI data gets corrupted because both SPI buses are active
at the same time. Since the SPI accesses aren't atomic, if an interrupt occurs
before the SPI data register is read, its possible that the data will be
changed after the ISR exits. There is also the issue of the Wiznet chip. If the
chip is selected, then it does not properly release MISO which will corrupt any
other device on the SPI. If an interrupt occurs while the Wiznet chip is being
accessed, and there is an SPI access to a different chip, the access to the
other chip will be corrupted because of a data collision on MISO.
What version of the Arduino software are you using? On what operating
system? Which Arduino board are you using?
Arduino IDE version 0021. Windows XP. Custom board.
Please provide any additional information below.
An example of a fix would be:
uint8_t W5100Class::read(uint16_t _addr)
{
// DISABLE INTERRUPTS
cli();
setSS();
SPI.transfer(0x0F);
SPI.transfer(_addr >> 8);
SPI.transfer(_addr & 0xFF);
uint8_t _data = SPI.transfer(0);
resetSS();
// ENABLE INTERRUPTS
sei();
return _data;
}
Original issue reported on code.google.com by akiba.fr...@gmail.com on 21 Oct 2010 at 12:39
Original issue reported on code.google.com by
akiba.fr...@gmail.comon 21 Oct 2010 at 12:39