TX Power¶

TX power, short for transmit power, is a parameter used to set a desired output power during packet transmissions. The TX power level is programmable at run-time and will only take effect on the next transmission.

TX Power Configuration¶

The default values for all parameters are usually measured by Texas Instruments for a specific front-end configuration on TI LaunchPads hardware; if instead a custom board is used the values will need to be re-tuned for the specific custom hardware.

TX Power Tables¶

TX power configuration is usually done by SysConfig or by code export in SmartRF Studio. A default TX power configuration is set, in addition to a TX power table being configured/exported alongside the settings.

For example if you are using SysConfig and leave the txPower undefined, or as default then the RCL_CmdGenericTx struct will use RCL_CmdGenericTx_Default() which sets the TX power to 0 dBm:

Listing 24. Default configuration for the generic transmit command, found in the generic.h file.¶

    #define RCL_CmdGenericTx_Default()                      \
{                                                           \
    .common = RCL_Command_Default(RCL_CMDID_GENERIC_TX,     \
                                RCL_Handler_Generic_Tx),    \
    .rfFrequency = 2440000000U,                             \
    .txBuffers = { 0 },                                     \
    .syncWord = 0x930B51DE,                                 \
    .txPower = {.dBm = 0, .fraction = 0},                   \
    .config = {                                             \
        .fsOff = 1,                                         \
        .reserved = 0,                                      \
    },                                                      \
}

A TX power table is a lookup table of all TX power table entries which are characterized for the given RF front-end configuration. A TX power table entry is a key-value pair, where the key is a human-readable power level in dBm and the value a TX power configuration value. You can find a example of the TX power table in rcl_settings.c as LRF_txPowerTable.

If you generate or export any RF settings for CC23xx, depending on which RF front-end configuration you are using, you will see in rcl_settings.c in a new array called LRF_txPowerTable with the following syntax:

Note

When exporting new RF configs with SmartRF Studio on the code export page, if you select Use PHY abbreviation the file naming will change from rcl_settings.c to rcl_settings_msk_250_kbps.c for example (the new name depends on which example, and custom naming you use in SmartRF Studio PHYs).

Listing 25. Tx power table obtained from SmartRF Studio 8 code export - it shows the internal structure of how the transmit power is generated.¶

// LRF_TxPowerTable data structure
const LRF_TxPowerTable LRF_txPowerTable = {
    .numEntries            = 0x0000000E,
    .powerTable            = {
        { .power = { .fraction = 0, .dBm = -20 }, .tempCoeff = 0, .value = { .reserved = 0, .ib = 18, .gain = 0, .mode = 0, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = -16 }, .tempCoeff = 0, .value = { .reserved = 0, .ib = 20, .gain = 1, .mode = 0, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = -12 }, .tempCoeff = 5, .value = { .reserved = 0, .ib = 17, .gain = 3, .mode = 0, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = -8 }, .tempCoeff = 12, .value = { .reserved = 0, .ib = 17, .gain = 4, .mode = 0, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = -4 }, .tempCoeff = 25, .value = { .reserved = 0, .ib = 17, .gain = 5, .mode = 0, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = 0 }, .tempCoeff = 40, .value = { .reserved = 0, .ib = 19, .gain = 6, .mode = 0, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = 1 }, .tempCoeff = 65, .value = { .reserved = 0, .ib = 30, .gain = 6, .mode = 0, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = 2 }, .tempCoeff = 41, .value = { .reserved = 0, .ib = 39, .gain = 4, .mode = 1, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = 3 }, .tempCoeff = 43, .value = { .reserved = 0, .ib = 31, .gain = 5, .mode = 1, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = 4 }, .tempCoeff = 50, .value = { .reserved = 0, .ib = 37, .gain = 5, .mode = 1, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = 5 }, .tempCoeff = 55, .value = { .reserved = 0, .ib = 27, .gain = 6, .mode = 1, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = 6 }, .tempCoeff = 75, .value = { .reserved = 0, .ib = 38, .gain = 6, .mode = 1, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = 7 }, .tempCoeff = 80, .value = { .reserved = 0, .ib = 25, .gain = 7, .mode = 1, .noIfampRfLdoBypass = 0 } },
        { .power = { .fraction = 0, .dBm = 8 }, .tempCoeff = 180, .value = { .reserved = 0, .ib = 63, .gain = 7, .mode = 1, .noIfampRfLdoBypass = 0 } }
    }
};

Programming the TX Power Level¶

In the proprietary RF examples, the desired tx power is set via SysConfig or by setting the txPower parameter in code.

An example on how you can set the txPower parameter in code before calling RCL_Command_submit():

RCL_CmdGenericTxTest   txCmd;
... //define application code here, use rfpacketTX example to start off with
txCmd.txPower.dBm = txpow;      // Set the TX power in dBm
... //send the packet