From f4dad87fd9cfd0b33454e9843f81290bb6ff81cb Mon Sep 17 00:00:00 2001 From: Robert Jordens Date: Tue, 6 Mar 2018 11:09:45 +0000 Subject: [PATCH] coredevice: add pcf8574a driver I2C IO expander with 8 quasi-bidirectional pins --- artiq/coredevice/pcf8574a.py | 47 +++++++++++++++++++++++++++ doc/manual/core_drivers_reference.rst | 6 ++++ 2 files changed, 53 insertions(+) create mode 100644 artiq/coredevice/pcf8574a.py diff --git a/artiq/coredevice/pcf8574a.py b/artiq/coredevice/pcf8574a.py new file mode 100644 index 000000000..ed11cc311 --- /dev/null +++ b/artiq/coredevice/pcf8574a.py @@ -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 diff --git a/doc/manual/core_drivers_reference.rst b/doc/manual/core_drivers_reference.rst index e55d6a79f..4185ddc47 100644 --- a/doc/manual/core_drivers_reference.rst +++ b/doc/manual/core_drivers_reference.rst @@ -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 ------------------------------------