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Feature/add no addr reads #22

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Feature/add no addr reads #22

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e16d59d
Add ability to perform i2c reads without register access to MicroPyth…
malcolm-sparkfun Nov 11, 2024
8d96ae2
add default arg for CircuitPython readByte
malcolm-sparkfun Nov 11, 2024
1151575
add __i2c_rdwr__ functions for MicroPython and CircuitPython for comp…
malcolm-sparkfun Nov 13, 2024
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34 changes: 30 additions & 4 deletions qwiic_i2c/circuitpy_i2c.py
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Original file line number Diff line number Diff line change
Expand Up @@ -162,7 +162,10 @@ def readWord(self, address, commandCode):
buffer = bytearray(2)

try:
self._i2cbus.writeto_then_readfrom(address, bytes([commandCode]), buffer)
if (commandCode == None):
self._i2cbus.readfrom_into(address, buffer) # TODO: not yet validated...
else:
self._i2cbus.writeto_then_readfrom(address, bytes([commandCode]), buffer)
except Exception as e:
self._i2cbus.unlock()
raise e
Expand All @@ -176,14 +179,17 @@ def read_word(self, address, commandCode):
return self.readWord(address, commandCode)

#----------------------------------------------------------
def readByte(self, address, commandCode):
def readByte(self, address, commandCode = None):
if not self._i2cbus.try_lock():
raise Exception("Unable to lock I2C bus")

buffer = bytearray(1)

try:
self._i2cbus.writeto_then_readfrom(address, bytes([commandCode]), buffer)
if (commandCode == None):
self._i2cbus.readfrom_into(address, buffer) # TODO: not yet validated...
else:
self._i2cbus.writeto_then_readfrom(address, bytes([commandCode]), buffer)
except Exception as e:
self._i2cbus.unlock()
raise e
Expand All @@ -203,7 +209,10 @@ def readBlock(self, address, commandCode, nBytes):
buffer = bytearray(nBytes)

try:
self._i2cbus.writeto_then_readfrom(address, bytes([commandCode]), buffer)
if (commandCode == None):
self._i2cbus.readfrom_into(address, buffer) # TODO: not yet validated...
else:
self._i2cbus.writeto_then_readfrom(address, bytes([commandCode]), buffer)
except Exception as e:
self._i2cbus.unlock()
raise e
Expand Down Expand Up @@ -332,3 +341,20 @@ def scan(self):
self._i2cbus.unlock()

return devices

#-----------------------------------------------------------------------
# Custom method for reading +8-bit register using `i2c_msg` from `smbus2`
#
# Designed to have same operation as the __i2c_rdwr method in linux_i2c.py
def __i2c_rdwr__(self, address, write_message, read_nbytes):
"""
Custom method used for 16-bit (or greater) register reads
:param address: 7-bit address
:param write_message: list with register(s) to read
:param read_nbytes: number of bytes to be read

:return: response of read transaction
:rtype: list
"""
self._i2cbus.readBlock(address, write_message, read_nbytes)
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This does not work in CircuitPython


35 changes: 33 additions & 2 deletions qwiic_i2c/micropython_i2c.py
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Original file line number Diff line number Diff line change
Expand Up @@ -117,19 +117,29 @@ def __setattr__(self, name, value):

# read commands ----------------------------------------------------------
def readWord(self, address, commandCode):
buffer = self._i2cbus.readfrom_mem(address, commandCode, 2)
if (commandCode == None):
buffer = self._i2cbus.readfrom(address, 2)
else:
buffer = self._i2cbus.readfrom_mem(address, commandCode, 2)

return (buffer[1] << 8 ) | buffer[0]

def read_word(self, address, commandCode):
return self.readWord(address, commandCode)

def readByte(self, address, commandCode):
def readByte(self, address, commandCode = None):
if (commandCode == None):
return self._i2cbus.readfrom(address, 1)[0]

return self._i2cbus.readfrom_mem(address, commandCode, 1)[0]

def read_byte(self, address, commandCode = None):
return self.readByte(address, commandCode)

def readBlock(self, address, commandCode, nBytes):
if (commandCode == None):
return self._i2cbus.readfrom(address, nBytes)

return self._i2cbus.readfrom_mem(address, commandCode, nBytes)

def read_block(self, address, commandCode, nBytes):
Expand Down Expand Up @@ -182,3 +192,24 @@ def ping(self, devAddress):
def scan(self):
""" Returns a list of addresses for the devices connected to the I2C bus."""
return self._i2cbus.scan()

#-----------------------------------------------------------------------
# Custom method for reading +8-bit register using `i2c_msg` from `smbus2`
#
# Designed to have same operation as the __i2c_rdwr method in linux_i2c.py
def __i2c_rdwr__(self, address, write_message, read_nbytes):
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This method should be changed. I know this is what was used elsewhere, but it's not a great name. Should match the conventions of the other methods in this driver, and get added to i2c_driver.py and linux_i2c.py. Then any device drivers that use it (I think just the VL53?) should be changed to use this new method. Does that make sense?

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@santaimpersonator santaimpersonator Nov 20, 2024 •
edited
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The naming convention was based off the original i2c_rdwr() method from the smbus2 Python package that this package utilizes as the driver on Linux platforms:

def i2c_rdwr(self, *i2c_msgs):

When we added this method, I included the double underscores (__) to give it a private attribute. This keeps the method hidden (in a way), since we were only using it for the VL53L1x. Additionally, the method wasn't considered a feature of the package, as noted in the README.md file of the smbus2 GitHub repository, :

Note

Starting with v0.2, the smbus2 library also has support for combined read and write transactions. i2c_rdwr is not really a SMBus feature but comes in handy when the master needs to:

  1. read or write bulks of data larger than SMBus' 32 bytes limit.
  2. write some data and then read from the slave with a repeated start and no stop bit between.

Each operation is represented by a i2c_msg message object.

As a recommendation... I'd keep the __i2c_rdwr__()method for backwards compatibility. Since it is technically private, we could create a new public method with the naming convention that you prefer. To keep the functionality, you could:

  • Call on the __i2c_rdwr__()method
  • Reuse the same code

"""
Custom method used for 16-bit (or greater) register reads
:param address: 7-bit address
:param write_message: list with register(s) to read
:param read_nbytes: number of bytes to be read

:return: response of read transaction
:rtype: list
"""

# micropython I2C doesn't have a corresponding "i2c_rdwr" function like smbus2, so we will make our own by passing stop=False to not send stop bits between repeated transfers
self._i2cbus.writeto(address, bytes(write_message), False)
return self._i2cbus.readfrom(address, read_nbytes)