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Switch/Router chip

Discussion in 'General Electronics Discussion' started by michcfr, Oct 29, 2012.

  1. michcfr

    michcfr

    5
    0
    Oct 29, 2012
    Hello,

    I am looking for a logic chip that does routing of pins signals like ethernet routers does with rj45 plugs.
    The router have to route 8 inputs to 32 outputs (or more). The signal is bidirectional like this:

    Y0...Y7 pins
    ^
    Router
    v
    Z0...Z31 pins

    The routing table Yi <=> Zj is stored in the memory of the router.

    Do you know a kind of chip that does this work?

    Regards,
    Michel
     
    Last edited: Oct 29, 2012
  2. Timescope

    Timescope

    43
    0
    Aug 30, 2012
    What type of signals do you want to switch ? You need to specify the voltages, frequency, pulse width etc.

    Timescope
     
  3. michcfr

    michcfr

    5
    0
    Oct 29, 2012
    I want to switch signals between pins of a STM32F MCU
    It includes TTL signals but also ADC,DAC and PWM pins.
     
  4. Timescope

    Timescope

    43
    0
    Aug 30, 2012
    There was a similar question here way back in 2005 Electronics Point and a 4051 analog switch solved the problem also recently at another forum electronics.stackexchange.com, crosspoint switches and crossbar switches were suggested. I searched for "mixed signal cross point switches" and found GM62093A
    which is a 12 x 8 crosspoint switch.
    Analog Devices and Maxim also have a range of switches.

    Timescope
     
  5. michcfr

    michcfr

    5
    0
    Oct 29, 2012
    Thank you for yout complete response!
    Since I would need something like 100pinsx100pins crosspoint switch, I think CPLD is more appropriate.
    I have been suggested to use low cost CPLD like the MACHX02 from Lattice, or CoolRunner from Xilinx.

    Does CPLD accepts bi-directional signals and analog signals?


    thank you
    michel
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

    9,136
    1,844
    Nov 17, 2011
    A CPLD could be made to accept bidirectional signals, but not analog. For analog signals an analog switch is best suited.
    You could use this slightly exotic 8x8 analog crosspoint.

    What is the application? What 100x100 signals do you need to switch? Do you need to switch them again and again or do you want to configure a one-time setup?
     
  7. michcfr

    michcfr

    5
    0
    Oct 29, 2012
    Hello Harald,

    I want to connect to my MCU many modules that uses different and various kind of interfaces: I2C,I2S,SPI,ADC,DAC,PWM,USB...

    I don't want to struggle with wiring.
    I just want to connect all I/O pins of these modules to the 100pins of the crosspoint switch and the I/O ports of the MCU to the other 100pins of the crosspoint switch.

    Then, at startup, the MCU configure the crosspoint switch to 'wire' the pins of modules with pins of the MCU I/O. It is configured each time the MCU is powered on.


    Regards,
    Michel
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

    9,136
    1,844
    Nov 17, 2011
    Excuse me, but that doesn't seem to be a sensible way of doing it. It can be done by a matrix of analog switches. These, however, may not be fast enough for high speed digital communication.

    I suggest you group the signals by function (e.g. analog, low speed digital, high speed digital) amd use a separate, much smaller matrix for each signal.

    You may end up struggling more with the switch matrix (or matrices) than with conventional wiring since the matrix will in any case introduce delays and/or signal distortions.

    Regards,
    Harald
     
  9. michcfr

    michcfr

    5
    0
    Oct 29, 2012
    Hello Harald,

    Thank you for your response.

    So I will get three groups: one for I2C,SPI,I2S,UART,USART signals as low speed, one for USB as high speed and the third for analog signals?
    Do you consider I2C,SPI,I2S,UART,USART as high or low speed?

    Since distance between the modules and the MCU are very short, 3-5cm, do you think thee will be significant delays and distorsions?

    regards
    michel
     
  10. Harald Kapp

    Harald Kapp Moderator Moderator

    9,136
    1,844
    Nov 17, 2011
    These could run under "slow".

    My concern was more about delays within the switch matrix. By keeping the matrix small and using fast components you can minimize these delays. Also, if you're using active components you can keep signal distortion at a minimum.

    Whether a signal is distorted is not only a matter of distance but also of the signal speed, especially rise time and fall time and the construction of the wiring. There is a reason why high frequency signals use coaxial wiring or microstrip lines on PCBs.

    In your case some careful layout (pair signals with the corresponding ground, keep wire loops as small as possible etc.). You may Google "guidelines for high speed signal wiring" if you're interested in more details.
     
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