i2c: refactor common operations

This commit is contained in:
Robert Jördens 2018-06-18 09:34:04 +00:00
parent 0e640a6d6f
commit 21a48711ec
1 changed files with 109 additions and 30 deletions

View File

@ -33,6 +33,110 @@ def i2c_read(busno: TInt32, ack: TBool) -> TInt32:
raise NotImplementedError("syscall not simulated")
@kernel
def i2c_poll(busno, busaddr):
"""Poll I2C device at address.
:param busno: I2C bus number
:param busaddr: 8 bit I2C device address (LSB=0)
:returns: True if the poll was ACKed
"""
i2c_start(busno)
ack = i2c_write(busno, busaddr)
i2c_stop(busno)
return ack
@kernel
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)
@kernel
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
@kernel
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)
@kernel
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)
class PCA9548:
"""Driver for the PCA9548 I2C bus switch.
@ -53,14 +157,7 @@ class PCA9548:
:param mask: Bit mask of enabled channels
"""
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, mask):
raise I2CError("PCA9548 failed to ack control word")
finally:
i2c_stop(self.busno)
i2c_write_byte(self.busno, self.address, mask)
@kernel
def set(self, channel):
@ -72,15 +169,7 @@ class PCA9548:
@kernel
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
return i2c_read_byte(self.busno, self.address)
class TCA6424A:
@ -97,19 +186,9 @@ class TCA6424A:
self.address = address
@kernel
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 _write24(self, addr, value):
i2c_write_many(self.busno, self.address, addr,
[value >> 16, value >> 8, value])
@kernel
def set(self, outputs):