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CC3100 - Limit Max TX power in Station role

Nirke
Intellectual 750 points
Other Parts Discussed in Thread: CC3100

Hey,

We are working with the CC3100 in Station role and connect to nearby APs.

As much as we know, the CC3100 automatically changes the bit rate & tx power it uses according to what it senses from the environment.

We need to make sure that the CC3100 doesn't exceed a certain TX power level.

How can we do it? Is there any way to do so?

Thanks,

Nir

  • 0
    TI__Mastermind 18455 points
    Hi Nir,

    Yes, you can use the "sl_WlanSet()" API with the "WLAN_GENERAL_PARAM_OPT_STA_TX_POWER" parameter in order to limit the Tx power.

    For further details you can refer to the CC3100 programmers guide: processors.wiki.ti.com/.../CC31xx_Programmers_Guide
    Or to the API doxygen: software-dl.ti.com/.../index.html

    Thanks,
    Alon
  • 0 in reply to Alon Srednizki
    Intellectual 750 points

    Hey Alon,

    Thank you for the fast reply.

    Still we don't understand how do we know what is the maximal transmit power in dBm when we use that API.

    According to the 2nd link you sent, see the emphasized text:

    Set STA mode Tx power level example:
 
Number between 0-15, as dB offset from max power (0 will set MAX power)
unsigned char  stapower=(unsigned char)power;
sl_WlanSet(SL_WLAN_CFG_GENERAL_PARAM_ID, WLAN_GENERAL_PARAM_OPT_STA_TX_POWER,1,(unsigned char *)&stapower);

    => "Number between 0-15, as dB offset from max power (0 will set MAX power)"

    Does it mean that for example with the below settings, the maximal transmission power will be ~3dBm for 1DSSS?

    unsigned char  stapower=15; // <= Set for 15dB less than max possible power
sl_WlanSet(SL_WLAN_CFG_GENERAL_PARAM_ID, WLAN_GENERAL_PARAM_OPT_STA_TX_POWER,1,(unsigned char *)&stapower);

    But according to CC3100 Datasheet (page 12) every TX_Power parameter value (0-15) yields a transmission power that is no less than 12.5dBm:

    Given that we don't control what bit rate the CC3100 will use for the transmission and we know that for each bit rate the tx power parameter (0-15) gives a different transmission power changes (in dBm), how can we ensure that it won't pass a certain tx power (dBm) without dependency of the chosen bit rate? 

    Does the 'WLAN_GENERAL_PARAM_OPT_STA_TX_POWER' definition is different than 'TX Power level' mentioned in the datasheet's graphs?

    Thanks,

    Nir

  • 0 in reply to Nirke
    TI__Mastermind 18455 points
    Hi Nir,

    The description in the DS is correct.
    You can't control the Tx power in a higher granularity than that.
    Meaning, you can't control the exact power per rate, per channel, but only reduced the maximum output power of the device, covering all channels and rates.

    Thanks,
    Alon