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machine.I2C

Classes

`I2C`	Construct and return a new I2C object using the following parameters:
`SoftI2C`	Construct a new software I2C object. The parameters are:

Module Contents

Construct and return a new I2C object using the following parameters:

id identifies a particular I2C peripheral. Allowed values for depend on the particular port/board

scl should be a pin object specifying the pin to use for SCL.

sda should be a pin object specifying the pin to use for SDA.

freq should be an integer which sets the maximum frequency for SCL.

timeout is the maximum time in microseconds to allow for I2C transactions. This parameter is not allowed on some ports.

Note that some ports/boards will have default values of scl and sda that can be changed in this constructor. Others will have fixed values of scl and sda that cannot be changed.

deinit() → None

Turn off the I2C bus.

Availability: WiPy.

init(scl, sda, *, freq=400000) → None

Initialise the I2C bus with the given arguments:

scl is a pin object for the SCL line

sda is a pin object for the SDA line

freq is the SCL clock rate

In the case of hardware I2C the actual clock frequency may be lower than the requested frequency. This is dependent on the platform hardware. The actual rate may be determined by printing the I2C object.

readfrom(addr, nbytes, stop=True) → bytes: Read nbytes from the peripheral specified by addr. If stop is true then a STOP condition is generated at the end of the transfer. Returns a bytes object with the data read.

readfrom_into(addr, buf, stop=True) → None

Read into buf from the peripheral specified by addr. The number of bytes read will be the length of buf. If stop is true then a STOP condition is generated at the end of the transfer.

The method returns None.

readfrom_mem(addr, memaddr, nbytes, *, addrsize=8) → bytes: Read nbytes from the peripheral specified by addr starting from the memory address specified by memaddr. The argument addrsize specifies the address size in bits. Returns a bytes object with the data read.

readfrom_mem_into(addr, memaddr, buf, *, addrsize=8) → None

Read into buf from the peripheral specified by addr starting from the memory address specified by memaddr. The number of bytes read is the length of buf. The argument addrsize specifies the address size in bits (on ESP8266 this argument is not recognised and the address size is always 8 bits).

The method returns None.

readinto(buf, nack=True) → Incomplete: Reads bytes from the bus and stores them into buf. The number of bytes read is the length of buf. An ACK will be sent on the bus after receiving all but the last byte. After the last byte is received, if nack is true then a NACK will be sent, otherwise an ACK will be sent (and in this case the peripheral assumes more bytes are going to be read in a later call).

scan() → List: Scan all I2C addresses between 0x08 and 0x77 inclusive and return a list of those that respond. A device responds if it pulls the SDA line low after its address (including a write bit) is sent on the bus.

start() → None: Generate a START condition on the bus (SDA transitions to low while SCL is high).

stop() → None: Generate a STOP condition on the bus (SDA transitions to high while SCL is high).

write(buf) → int: Write the bytes from buf to the bus. Checks that an ACK is received after each byte and stops transmitting the remaining bytes if a NACK is received. The function returns the number of ACKs that were received.

writeto(addr, buf, stop=True) → int: Write the bytes from buf to the peripheral specified by addr. If a NACK is received following the write of a byte from buf then the remaining bytes are not sent. If stop is true then a STOP condition is generated at the end of the transfer, even if a NACK is received. The function returns the number of ACKs that were received.

writeto_mem(addr, memaddr, buf, *, addrsize=8) → None

Write buf to the peripheral specified by addr starting from the memory address specified by memaddr. The argument addrsize specifies the address size in bits (on ESP8266 this argument is not recognised and the address size is always 8 bits).

The method returns None.

writevto(addr, vector, stop=True) → int

Write the bytes contained in vector to the peripheral specified by addr. vector should be a tuple or list of objects with the buffer protocol. The addr is sent once and then the bytes from each object in vector are written out sequentially. The objects in vector may be zero bytes in length in which case they don’t contribute to the output.

If a NACK is received following the write of a byte from one of the objects in vector then the remaining bytes, and any remaining objects, are not sent. If stop is true then a STOP condition is generated at the end of the transfer, even if a NACK is received. The function returns the number of ACKs that were received.

class machine.I2C.SoftI2C(scl, sda, *, freq=400000, timeout=50000)

Bases: I2C

Construct a new software I2C object. The parameters are:

scl should be a pin object specifying the pin to use for SCL.

sda should be a pin object specifying the pin to use for SDA.

freq should be an integer which sets the maximum frequency for SCL.

timeout is the maximum time in microseconds to wait for clock stretching (SCL held low by another device on the bus), after which an OSError(ETIMEDOUT) exception is raised.