coredevice: add pcf8574a driver

I2C IO expander with 8 quasi-bidirectional pins
This commit is contained in:
Robert Jördens 2018-03-06 11:09:45 +00:00 committed by Robert Jordens
parent 62af7fe2ac
commit f4dad87fd9
2 changed files with 53 additions and 0 deletions

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@ -0,0 +1,47 @@
from artiq.experiment import kernel
from artiq.coredevice.i2c import (
i2c_start, i2c_write, i2c_read, i2c_stop, I2CError)
class PCF8574A:
"""Driver for the PCF8574 I2C remote 8-bit I/O expander.
I2C transactions not real-time, and are performed by the CPU without
involving RTIO.
"""
def __init__(self, dmgr, busno=0, address=0x7c, core_device="core"):
self.core = dmgr.get(core_device)
self.busno = busno
self.address = address
@kernel
def set(self, data):
"""Drive data on the quasi-bidirectional pins.
:param data: Pin data. High bits are weakly driven high
(and thus inputs), low bits are strongly driven low.
"""
i2c_start(self.busno)
try:
if not i2c_write(self.busno, self.address):
raise I2CError("PCF8574A failed to ack address")
if not i2c_write(self.busno, data):
raise I2CError("PCF8574A failed to ack data")
finally:
i2c_stop(self.busno)
@kernel
def get(self):
"""Retrieve quasi-bidirectional pin input data.
:return: Pin data
"""
i2c_start(self.busno)
ret = 0
try:
if not i2c_write(self.busno, self.address | 1):
raise I2CError("PCF8574A failed to ack address")
ret = i2c_read(self.busno, False)
finally:
i2c_stop(self.busno)
return ret

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@ -45,6 +45,12 @@ These drivers are for the core device and the peripherals closely integrated int
.. automodule:: artiq.coredevice.i2c
:members:
:mod:`artiq.coredevice.pcf8574a` module
---------------------------------------
.. automodule:: artiq.coredevice.pcf8574a
:members:
:mod:`artiq.coredevice.cache` module
------------------------------------