def begin(irq):
"""
This function opens the SPI connection available on the Raspberry Pi using the chip select #0. Normally, spidev can auto enable chip select when necessary. However, in our case, the dw1000's chip select is connected to GPIO16 so we have to enable/disable it manually.
It also sets up the interrupt detection event on the rising edge of the interrupt pin.
Args:
irq : The GPIO pin number managing interrupts.
"""
global _deviceMode
# Wait 5 us to open spi connection to let the chip enter idle state, see 2.3.2 of the DW1000 user manual (INIT).
time.sleep(C.INIT_DELAY)
GPIO.setmode(GPIO.BCM)
spi.open(0, 0)
# spi.max_speed_hz = 4000000
_deviceMode = C.IDLE_MODE
GPIO.setup(irq, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.add_event_detect(irq, GPIO.RISING, callback=handleInterrupt)
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