def _write24(self, command, value):
i2c_start(self.busno)
try:
if not i2c_write(self.busno, self.address):
raise I2CError("TCA6424A failed to ack address")
if not i2c_write(self.busno, command):
raise I2CError("TCA6424A failed to ack command")
for i in range(3):
if not i2c_write(self.busno, value >> 16):
raise I2CError("TCA6424A failed to ack data")
value <<= 8
finally:
i2c_stop(self.busno)
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)
def i2c_write_byte(busno, busaddr, data, ack=True):
"""Write one byte to a device.
:param busno: I2C bus number
:param busaddr: 8 bit I2C device address (LSB=0)
:param data: Data byte to be written
:param nack: Allow NACK
"""
i2c_start(busno)
try:
if not i2c_write(busno, busaddr):
raise I2CError("failed to ack bus address")
if not i2c_write(busno, data) and ack:
raise I2CError("failed to ack write data")
finally:
i2c_stop(busno)
def set(self, channel):
"""Select one channel.
Selecting multiple channels at the same time is not supported by this
driver.
:param channel: channel number (0-7)
"""
i2c_start(self.busno)
try:
if not i2c_write(self.busno, self.address):
raise I2CError("PCA9548 failed to ack address")
if not i2c_write(self.busno, 1 << channel):
raise I2CError("PCA9548 failed to ack control word")
finally:
i2c_stop(self.busno)
def readback(self):
i2c_start(self.busno)
r = 0
try:
if not i2c_write(self.busno, self.address | 1):
raise I2CError("PCA9548 failed to ack address")
r = i2c_read(self.busno, False)
finally:
i2c_stop(self.busno)
return r
def i2c_write_many(busno, busaddr, addr, data, ack_last=True):
"""Transfer multiple bytes to a device.
:param busno: I2c bus number
:param busaddr: 8 bit I2C device address (LSB=0)
:param addr: 8 bit data address
:param data: Data bytes to be written
:param ack_last: Expect I2C ACK of the last byte written. If `False`,
the last byte may be NACKed (e.g. EEPROM full page writes).
"""
n = len(data)
i2c_start(busno)
try:
if not i2c_write(busno, busaddr):
raise I2CError("failed to ack bus address")
if not i2c_write(busno, addr):
raise I2CError("failed to ack data address")
for i in range(n):
if not i2c_write(busno, data[i]) and (i < n - 1 or ack_last):
raise I2CError("failed to ack write data")
finally:
i2c_stop(busno)
def i2c_read_many(busno, busaddr, addr, data):
"""Transfer multiple bytes from a device.
:param busno: I2c bus number
:param busaddr: 8 bit I2C device address (LSB=0)
:param addr: 8 bit data address
:param data: List of integers to be filled with the data read.
One entry ber byte.
"""
m = len(data)
i2c_start(busno)
try:
if not i2c_write(busno, busaddr):
raise I2CError("failed to ack bus address")
if not i2c_write(busno, addr):
raise I2CError("failed to ack data address")
i2c_restart(busno)
if not i2c_write(busno, busaddr | 1):
raise I2CError("failed to ack bus read address")
for i in range(m):
data[i] = i2c_read(busno, ack=i < m - 1)
finally:
i2c_stop(busno)
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
def i2c_read_byte(busno, busaddr):
"""Read one byte from a device.
:param busno: I2C bus number
:param busaddr: 8 bit I2C device address (LSB=0)
:returns: Byte read
"""
i2c_start(busno)
data = 0
try:
if not i2c_write(busno, busaddr | 1):
raise I2CError("failed to ack bus read address")
data = i2c_read(busno, ack=False)
finally:
i2c_stop(busno)
return data