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I2C with a cc2541EMK on a Soc_BB, is it grounded?

Luke Spencer
Prodigy 115 points
Other Parts Discussed in Thread: CC2541EMK, CC2541, CC2540

I desire to use the I2C features of my CC2541EMK which is powered by a SoC_BB. 

However when looking at the schematic layout of the CC2541EMK (http://pdf1.alldatasheet.com/datasheet-pdf/view/466992/TI1/CC2541EMK.html) and the schematic for the SoC_BB (http://www.ti.com/lit/ug/swru241/swru241.pdf) it appears the I2C pins SCL and SDA have been grounded on the SoC_BB, yet have pull up resistors on the EMK.

Have we made a mistake in seeing this? and if so which of the SoC_BB P10 and P11 pins are used for the SCL and SDA?

Regards, 

  • 0
    TI__Genius 12545 points

    Luke,

    Unfortunately you are right. The I2C lines from the CC2541EM are connected to ground on the SoC-BB. If you are measuring current consumption of the CC2541, I'd advise you to remove the pull up resistors and set the I2C lines as output low GPIOs.

    The SoC-BB was made for simple tasks of debugging the different TI LPRF SoCs along with access to the different GPIOs. It was not made to cover the extra functions of the I2C in the case of the CC2541 or the USB in the case of the CC2540.

    If you plan to use the I2C on the CC2541EM, you should use the SmartRF05EB (http://www.ti.com/lit/ug/swru210a/swru210a.pdf) instead.

    Sorry for the inconvenience

  • 0 in reply to Chatto
    Prodigy 115 points

    Hello Chatto,

    Thank you very much for your response. That is quite frustrating, but we should be able to hack the board to separate the I2C pins before they get to SoC_BB.

    Was there any other compatibility issues in terms of using the bluetooth and ADC pins which is not highlighted as well? These are also essential to the project we are developing and would be nice to confirm they are not issues we will come across in the next couple of weeks. 

    Regards,

    Luke

  • 0 in reply to Luke Spencer
    TI__Guru** 106705 points

    Hi Luke,

    Attached are the schematics for the SoC_BB and also the CC2541EM schematic.

    On the SoC_BB you should be able to cut the traces going from the right side of P2 to ground with a scalpel (do not cut the trace from pin 2).

    Cheers,

    Fredrik

    7282.Schematic_p1_SOC_BB_1_1.pdf

    2548.CC2541EM_Schematic.pdf

  • 0 in reply to Fredrik K
    Prodigy 115 points

    Hi Fredrik,

    Thanks very much. Is it possible to get the PCB layout so I have exact measurements for a PCB i'm designing to go in between the boards to take out the I2C pins?

    Regards

    Luke

  • 0 in reply to Luke Spencer
    TI__Guru** 106705 points

    Hi Luke,

    This is an old board, and I am not sure where the layout files are. I do not know what additional information the layout would give you, everything you need to know is in the schematic.

    If you have any specific questions, do let me know.

    Cheers,

    Fredrik