class I2C -- 2线串行通信协议

I2C是一种两线通信设备之间的协议。在物理层包括2条线：SCL和SDA，时钟线和数据线分别。

创建I2C对象连接到一个特定的总线。他们可以在创建时初始化，或初始化后

例如:

from pyb import I2C

i2c = I2C(1)                         # create on bus 1
i2c = I2C(1, I2C.MASTER)             # create and init as a master
i2c.init(I2C.MASTER, baudrate=20000) # init as a master
i2c.init(I2C.SLAVE, addr=0x42)       # init as a slave with given address
i2c.deinit()                         # turn off the peripheral

打印I2C对象提供有关其配置的信息。

基本方法是发送和接收:

i2c.send('abc')      # send 3 bytes
i2c.send(0x42)       # send a single byte, given by the number
data = i2c.recv(3)   # receive 3 bytes

接收到位，首先创建一个ByteArray:

data = bytearray(3)  # create a buffer
i2c.recv(data)       # receive 3 bytes, writing them into data

可以指定超时（毫秒):

i2c.send(b'123', timeout=2000)   # timeout after 2 seconds

主机必须指定收件人地址:

i2c.init(I2C.MASTER)
i2c.send('123', 0x42)        # send 3 bytes to slave with address 0x42
i2c.send(b'456', addr=0x42)  # keyword for address

其它方法:

i2c.is_ready(0x42)           # check if slave 0x42 is ready
i2c.scan()                   # scan for slaves on the bus, returning
                             #   a list of valid addresses
i2c.mem_read(3, 0x42, 2)     # read 3 bytes from memory of slave 0x42,
                             #   starting at address 2 in the slave
i2c.mem_write('abc', 0x42, 2, timeout=1000) # write 'abc' (3 bytes) to memory of slave 0x42
                                            # starting at address 2 in the slave, timeout after 1 second

构造器

class pyb.I2C(bus, ...)

Construct an I2C object on the given bus. bus can be 1 or 2, 'X' or 'Y'. With no additional parameters, the I2C object is created but not initialised (it has the settings from the last initialisation of the bus, if any). If extra arguments are given, the bus is initialised. See init for parameters of initialisation.

The physical pins of the I2C busses on Pyboards V1.0 and V1.1 are:

  • I2C(1) is on the X position: (SCL, SDA) = (X9, X10) = (PB6, PB7)
  • I2C(2) is on the Y position: (SCL, SDA) = (Y9, Y10) = (PB10, PB11)

On the Pyboard Lite:

  • I2C(1) is on the X position: (SCL, SDA) = (X9, X10) = (PB6, PB7)
  • I2C(3) is on the Y position: (SCL, SDA) = (Y9, Y10) = (PA8, PB8)

Calling the constructor with 'X' or 'Y' enables portability between Pyboard types.

方法

I2C.deinit()

解除I2C定义。

I2C.init(mode, *, addr=0x12, baudrate=400000, gencall=False, dma=False)

初始化参数:

  • mode 只能是 I2C.MASTER 或者 I2C.SLAVE
  • addr 7位I2C地址(only sensible for a slave)
  • baudrate 时钟频率 (only sensible for a master)
  • gencall 通用调用模式
  • dma is whether to allow the use of DMA for the I2C transfers (note that DMA transfers have more precise timing but currently do not handle bus errors properly)
I2C.is_ready(addr)

检测I2C设备是否响应，只对主模式有效。

I2C.mem_read(data, addr, memaddr, *, timeout=5000, addr_size=8)

读取数据

  • data can be an integer (number of bytes to read) or a buffer to read into
  • addr is the I2C device address
  • memaddr is the memory location within the I2C device
  • timeout is the timeout in milliseconds to wait for the read
  • addr_size selects width of memaddr: 8 or 16 bits

返回读取数据 只对主模式有效。

I2C.mem_write(data, addr, memaddr, *, timeout=5000, addr_size=8)

Write to the memory of an I2C device:

  • data can be an integer or a buffer to write from
  • addr is the I2C device address
  • memaddr is the memory location within the I2C device
  • timeout is the timeout in milliseconds to wait for the write
  • addr_size selects width of memaddr: 8 or 16 bits

Returns None. This is only valid in master mode.

I2C.recv(recv, addr=0x00, *, timeout=5000)

Receive data on the bus:

  • recv can be an integer, which is the number of bytes to receive, or a mutable buffer, which will be filled with received bytes
  • addr is the address to receive from (only required in master mode)
  • timeout is the timeout in milliseconds to wait for the receive

Return value: if recv is an integer then a new buffer of the bytes received, otherwise the same buffer that was passed in to recv.

I2C.send(send, addr=0x00, *, timeout=5000)

Send data on the bus:

  • send is the data to send (an integer to send, or a buffer object)
  • addr is the address to send to (only required in master mode)
  • timeout is the timeout in milliseconds to wait for the send

Return value: None.

I2C.scan()

Scan all I2C addresses from 0x01 to 0x7f and return a list of those that respond. Only valid when in master mode.

Constants

I2C.MASTER

for initialising the bus to master mode

I2C.SLAVE

for initialising the bus to slave mode