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LMH1297: Using SigCon Architect through USB2ANY

Kawai
Guru 19785 points
Part Number: LMH1297
Other Parts Discussed in Thread: USB2ANY, , SIGCONARCHITECT, LMH1218EVM

Hi Team,

Please allow me to ask you about USB2ANY and SigCon Architect to control LMH1297 on my board.

My LMH1297 is using 2.5V for SMBus pull up voltage.

I would like to control the device with the external PC using SigCon Architect through USB2ANY.

Q1). Does SigCon Architect use the internal pull up in USB2ANY or is it only using USB2ANY as just an open drain output ?
- I believe USB2ANY has internal pull up on it's board which is connected to 3.3V. However, it depends on the software whether this pull up is used or not. 
- When started SigCon Architect with USB2ANY connected, I was able to see 3.3V output on the SDA and SCL line. However, I was not able to test the actual communication because it switches to Demo Mode.

Q2). To use SigCon Architect on my board, what do we need to do ?
  A). Remove 2.5V pull up on my board and connect USB2ANY to SMBus line. Does this work ?
  B). Remove 3.3V pull up inside the USB2ANY and connect it to the SMBus line.
  C). Other procedure ?

Best Regards,

Kawai

  • 0
    TI__Guru* 93670 points

    Hi Kawai-San,

    Q1). LMH1297EVM uses 3P3V either from VBUS(U2 pin 1) - provided on micro-USB connector - or pin 5  of J8. So in any case, 3P3V supply is provided for the SCL and SDA pull ups.

    Note in demo mode, there is no SMBus communication. SigconArchitect does not allow I2C communication while in demo mode.

    Q2). Remove 2.5V and let USB2ANY provide 3.3V supply as noted in #1 above.

    Regards,,nasser

  • 0 in reply to Nasser Mohammadi
    Guru 19785 points

    Hi Nasser-san,

    I understood that in the case of USB2ANY used with SigCon Architect, SMBus is always byassed (pulled up) inside the USB2ANY.
    * I asked this because when I used USB2ANY with "USB2ANY Explorer software" pull up was disabled.

    So, if we don't want to make modification on our board, I believe removing the pull up resistor on the USB2ANY could be another solution, am I correct ?

    Best Regards,

    Kawai

  • 0 in reply to Kawai
    TI__Guru* 93670 points

    Hi Kawai-San,

    I have used USB2ANY box with the LMH1218EVM. On USB2ANY software I turn on 3.3V supply. Then - this turns on 3.3V on USB2ANY connector. Under this condition - I was able to run LMH1218EVM GUI and I did not have to make any change on the LMH1218EVM.

    On your board, do you use USB2ANY box 3.3V to pull up your onboard SCL and SDA pins?

    Regards,,nasser

  • 0 in reply to Nasser Mohammadi
    Guru 19785 points

    Hi Nasser-san,

    There are FETs (Q2,Q4) between the 3.3V pull up and SMBus line in "USB2ANY".

    My question is that whether this FET is controlled "ON" or "OFF" by SigCon Architect.

    The FET gate signal is controlled from the MSP430 on USB2ANY. Since, USB2ANY only operate in emulation mode (DEMO mode, no signal) when it cannot talk to the slave device, there is no way for me to confirm from the hardware side. I would need to ask the specification of the SigCon Architect whether the software controls the Q2 and Q4 to turn on or not.

    I would like to clarify in specific for our future support.

    For now, we decided to remove the pull up resistors for SDA/SCL on USB2ANY, so that USB2ANY would only act as open drain. This way we would not need to remove 2.5V pull-up resistors on our board, or no current flow from USB2ANY 3.3V to our board 2.5V.

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Guru* 93670 points

    Hi Kawai-San,

    I don't think SigconArchitect GUI controls Q2 and Q3. We use pin 6 +3.3V EXT to pull up resistors on SDA and SCL of the LMH12xx evaluation boards.

    Also, please note you can take for example two LMH1218EVMs with one USB2ANY box. Then connect USB2ANY just to one of these LMH1218EVMs and use wires to connect from one LMH1218EVM SDA/SCL/GND lines to the next one. Using two different SMBus addresses you can use SigconArchitect GUI to control either of these boards. As you can see here the 2nd board is not even connected to the USB2ANY but you can talk to it - meaning no Q2 or Q3 for the 2nd evaluation board.

    Also, what you've done with respect to 2.5V supply and using USB2ANY SCL/SDA lanes as open drain with no pullup should work too.

    Regards,,nasser

  • 0 in reply to Nasser Mohammadi
    Guru 19785 points

    Hi Nasser-san,

    > Also, what you've done with respect to 2.5V supply and using USB2ANY SCL/SDA lanes as open drain with no pullup should work too.

    Thank you. I am closing this thread.


    > As you can see here the 2nd board is not even connected to the USB2ANY but you can talk to it - meaning no Q2 or Q3 for the 2nd evaluation board.

    I noticed that the pull ups on the LMH1297EVM could be un-wired by removing all the jumpers at J9. With this test, I was able to communicate with the LMH1297, meaning that USB2ANY internal pull ups are valid (FET Q2 and Q4 are turned ON from U4 MCU GPO).

    Best Regards,

    Kawai