mirror of https://github.com/m-labs/artiq
48 lines
1.4 KiB
Python
48 lines
1.4 KiB
Python
from artiq.experiment import kernel
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from artiq.coredevice.i2c import (
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i2c_start, i2c_write, i2c_read, i2c_stop, I2CError)
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class PCF8574A:
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"""Driver for the PCF8574 I2C remote 8-bit I/O expander.
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I2C transactions not real-time, and are performed by the CPU without
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involving RTIO.
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"""
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def __init__(self, dmgr, busno=0, address=0x7c, core_device="core"):
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self.core = dmgr.get(core_device)
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self.busno = busno
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self.address = address
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@kernel
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def set(self, data):
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"""Drive data on the quasi-bidirectional pins.
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:param data: Pin data. High bits are weakly driven high
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(and thus inputs), low bits are strongly driven low.
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"""
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i2c_start(self.busno)
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try:
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if not i2c_write(self.busno, self.address):
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raise I2CError("PCF8574A failed to ack address")
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if not i2c_write(self.busno, data):
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raise I2CError("PCF8574A failed to ack data")
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finally:
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i2c_stop(self.busno)
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@kernel
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def get(self):
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"""Retrieve quasi-bidirectional pin input data.
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:return: Pin data
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"""
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i2c_start(self.busno)
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ret = 0
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try:
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if not i2c_write(self.busno, self.address | 1):
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raise I2CError("PCF8574A failed to ack address")
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ret = i2c_read(self.busno, False)
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finally:
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i2c_stop(self.busno)
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return ret
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