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@ -9,86 +9,55 @@ level it consists of 2 wires: SCL and SDA, the clock and data lines respectively |
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I2C objects are created attached to a specific bus. They can be initialised |
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when created, or initialised later on. |
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.. only:: port_wipy |
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Printing the I2C object gives you information about its configuration. |
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Example:: |
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Example usage:: |
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from machine import I2C |
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from machine import I2C |
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i2c = I2C(0) # create on bus 0 |
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i2c = I2C(0, I2C.MASTER) # create and init as a master |
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i2c.init(I2C.MASTER, baudrate=20000) # init as a master |
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i2c.deinit() # turn off the peripheral |
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i2c = I2C(freq=400000) # create I2C peripheral at frequency of 400kHz |
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# depending on the port, extra parameters may be required |
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# to select the peripheral and/or pins to use |
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Printing the i2c object gives you information about its configuration. |
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i2c.scan() # scan for slaves, returning a list of 7-bit addresses |
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.. only:: port_wipy |
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i2c.writeto(42, b'123') # write 3 bytes to slave with 7-bit address 42 |
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i2c.readfrom(42, 4) # read 4 bytes from slave with 7-bit address 42 |
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A master must specify the recipient's address:: |
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i2c.init(I2C.MASTER) |
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i2c.writeto(0x42, '123') # send 3 bytes to slave with address 0x42 |
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i2c.writeto(addr=0x42, b'456') # keyword for address |
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Master also has other methods:: |
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i2c.scan() # scan for slaves on the bus, returning |
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# a list of valid addresses |
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i2c.readfrom_mem(0x42, 2, 3) # read 3 bytes from memory of slave 0x42, |
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# starting at address 2 in the slave |
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i2c.writeto_mem(0x42, 2, 'abc') # write 'abc' (3 bytes) to memory of slave 0x42 |
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# starting at address 2 in the slave, timeout after 1 second |
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i2c.readfrom_mem(42, 8, 3) # read 3 bytes from memory of slave 42, |
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# starting at memory-address 8 in the slave |
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i2c.writeto_mem(42, 2, b'\x10') # write 1 byte to memory of slave 42 |
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# starting at address 2 in the slave |
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Constructors |
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------------ |
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.. only:: port_wipy |
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.. class:: I2C(bus, ...) |
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Construct an I2C object on the given bus. `bus` can only be 0. |
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If the bus is not given, the default one will be selected (0). |
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.. class:: I2C(id=-1, \*, scl, sda, freq=400000) |
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.. only:: not port_wipy |
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Construct and return a new I2C object using the following parameters: |
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.. class:: I2C(id=-1, \*, scl, sda, freq=400000) |
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Construct and return a new I2C object using the following parameters: |
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- `id` identifies the particular I2C peripheral. The default |
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value of -1 selects a software implementation of I2C which can |
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work (in most cases) with arbitrary pins for SCL and SDA. |
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If `id` is -1 then `scl` and `sda` must be specified. Other |
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allowed values for `id` depend on the particular port/board, |
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and specifying `scl` and `sda` may or may not be required or |
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allowed in this case. |
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- `scl` should be a pin object specifying the pin to use for SCL. |
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- `sda` should be a pin object specifying the pin to use for SDA. |
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- `freq` should be an integer which sets the maximum frequency |
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for SCL. |
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- `id` identifies the particular I2C peripheral. The default |
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value of -1 selects a software implementation of I2C which can |
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work (in most cases) with arbitrary pins for SCL and SDA. |
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If `id` is -1 then `scl` and `sda` must be specified. Other |
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allowed values for `id` depend on the particular port/board, |
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and specifying `scl` and `sda` may or may not be required or |
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allowed in this case. |
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- `scl` should be a pin object specifying the pin to use for SCL. |
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- `sda` should be a pin object specifying the pin to use for SDA. |
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- `freq` should be an integer which sets the maximum frequency |
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for SCL. |
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General Methods |
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--------------- |
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.. only:: port_wipy |
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.. method:: I2C.init(mode, \*, baudrate=100000, pins=(SDA, SCL)) |
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Initialise the I2C bus with the given parameters: |
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.. method:: I2C.init(scl, sda, \*, freq=400000) |
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- ``mode`` must be ``I2C.MASTER`` |
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- ``baudrate`` is the SCL clock rate |
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- ``pins`` is an optional tuple with the pins to assign to the I2C bus. |
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Initialise the I2C bus with the given arguments: |
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.. only:: port_esp8266 |
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.. method:: I2C.init(scl, sda, \*, freq=400000) |
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Initialise the I2C bus with the given arguments: |
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- `scl` is a pin object for the SCL line |
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- `sda` is a pin object for the SDA line |
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- `freq` is the SCL clock rate |
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- `scl` is a pin object for the SCL line |
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- `sda` is a pin object for the SDA line |
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- `freq` is the SCL clock rate |
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.. method:: I2C.deinit() |
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@ -102,8 +71,6 @@ General Methods |
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those that respond. A device responds if it pulls the SDA line low after |
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its address (including a write bit) is sent on the bus. |
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Note: on WiPy the I2C object must be in master mode for this method to be valid. |
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Primitive I2C operations |
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------------------------ |
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@ -204,12 +171,3 @@ methods are convenience functions to communicate with such devices. |
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On WiPy the return value is the number of bytes written. Otherwise the |
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return value is `None`. |
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Constants |
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--------- |
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.. data:: I2C.MASTER |
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for initialising the bus to master mode |
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Availability: WiPy. |
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Damien George
8 years ago