• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 34 subscribers
  • Views 398 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCA9548A-Q1: Some questions about TCA9548A-Q1

?? ?
Prodigy 140 points
Part Number: TCA9548A-Q1
Other Parts Discussed in Thread: TCA9548A

HI，

1. We are going to use TCA9548A-Q1 to expand the I2C interface. If the expanded 8-way I2C interface is connected to different I2C address devices, can only one of the expanded interfaces SCX/SDX be connected to the SCL/SDA main interface at a time?Or 8 expansion I2C can be connected to SCL/SDA interface at the same time？
2. What are the advantages of TCA9548A-Q1 compared with analog switches？
3. A0/A1/A2 is used to set the I2C address of TCA9548A-Q1, right?
4. When communicating with the I2C device attached to the SCX/SDX interface, does the main SCL/SDA interface need to transmit two I2C addresses? First send the I2C address of TCA9548A-Q1 set by A0/A1/A2, and then send the I2C address of the device that connect to SCX/SAX?

  • 0
    TI__Guru 53555 points

    Hello,

    ?? ? said:
    1. We are going to use TCA9548A-Q1 to expand the I2C interface. If the expanded 8-way I2C interface is connected to different I2C address devices, can only one of the expanded interfaces SCX/SDX be connected to the SCL/SDA main interface at a time?Or 8 expansion I2C can be connected to SCL/SDA interface

    This device is used as a switch to connect or disconnect downstream devices on SDx/SCx channels from the I2C controller. If there are peripherals with shared addresses on separate downstream channels, only one such channel should be enabled when then the controller attempts to communicate with this address. All enabled channels are essentially connected to the main controller SDA/SCL lines, so all devices connected to enabled channels will see the commands sent by the controller. All disabled channels are not connected to the controller so such commands are not seen and thus ignored. 

    ?? ? said:
    2. What are the advantages of TCA9548A-Q1 compared with analog switches？

    I2C controlled switches such as TCA9548A allow the various channels to be controlled directly through the I2C interface. When compared to analog switches or multiplexers, this uses less IO pins. Since the I2C lines are already be used in such an application, the I2C switch will not require any additional MCU pins to control it. 

    ?? ? said:
    3. A0/A1/A2 is used to set the I2C address of TCA9548A-Q1, right?

    Correct. These pin states only impact the address of the I2C switch itself. It does not impact the effective address of any other I2C device on the network. 

    ?? ? said:
    4. When communicating with the I2C device attached to the SCX/SDX interface, does the main SCL/SDA interface need to transmit two I2C addresses? First send the I2C address of TCA9548A-Q1 set by A0/A1/A2, and then send the I2C address of the device that connect to SCX/SAX?

    No. Once the TCA9548A has enabled a SCx/SDx channel, that channel remains connected to the the SCL/SDA lines until the switch is reconfigured. This allows a single command to TCA9548A to enable the channel, then any number of individual commands can be sent to a downstream device without interfacing with the switch again. The switch only needs to be reconfigured when a peripheral on a different channel needs to be addressed. 

    Let me know if you have any more questions.

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    Prodigy 140 points

    Thank you for your reply.

    For the question4, If the main SCL/SDA interface does not send the address of the I2C device hanging on the SCX/SDX, how can the main SCL/SDA communicate with this device?

  • 0 in reply to ?? ?
    Guru 317080 points

    Once the TCA9548A has enabled a SCx/SDx channel, there is a direct electrical connection to that channel, i.e., the channel becomes part of the I²C bus. To access your device, just send the command bytes (including its address) normally.

  • 0 in reply to Clemens Ladisch
    Prodigy 140 points

    HI，

    Will the I2C channel switching speed of TCA9548A-Q1 be faster than the analog switch?

  • 0 in reply to ?? ?
    Guru 317080 points

    The speed is similar. But in any case, for a slow protocol like I²C, it does not matter.