[Tinyos-help] TinyOS-2.x - Controlling the Default Radio Power in Software

[Andy Dalton]

Greetings,

I'm looking to control the default radio power level at runtime for
Telos motes using TinyOS-2.x.  In tos/chips/cc2420/CC2420Power.nc I
see the following comment:

"[This] does not include transmission power, see the CC2420Config interface."

However, the CC2420Config interface does not include any command to
set the default radio power level.  The file
tos/chips/cc2420/CC2420ControlP.nc includes a state variable
'm_tx_power' that is initialized to CC2420_DEF_RFPOWER; however, that
variable is never used.  The file tos/chips/cc2420/CC2420TransmitP.nc
directly uses CC2420_DEF_RFPOWER to set the default power level:

    if ( !tx_power ) {
      // If our packet's tx_power wasn't configured to anything but 0,
      // send it using the default RF power.  This assumes the
      // packet's metadata is all set to 0's on boot.

      tx_power = CC2420_DEF_RFPOWER;
    }

It looks to me like the original intent was to provide a software
interface for setting the default radio power level via the
CC2420Config, but that its realization got lost along the way.  With
the current implementation, I cannot see a way to set the default
radio power in software.

One way to resolve this would be to add two new commands to the
CC2420Config interface:

    command uint8_t getDefaultTxPower();
    command void setDefaultTxPower(uint8_t txPower);

Then, in CC2420ControlP add implementations of those commands (again,
'm_tx_power' is already declared in this module and initialized to
CC2420_DEF_RFPOWER):

    command uint8_t CC2420Config.getDefaultTxPower() {
        return m_tx_power;
    }

    command uint8_t CC2420Config.setDefaultTxPower(uint8_t txPower) {
        m_tx_power = txPower;
    }

Then, in CC2420TransmitP use the CC2420Config interface, and call the
getDefaultTxPower command to set the default power:

    if ( !tx_power ) {
      // If our packet's tx_power wasn't configured to anything but 0,
      // send it using the default RF power.  This assumes the
      // packet's metadata is all set to 0's on boot.

      tx_power = call CC2420Config.getDefaultTxPower();
    }

Does this seem reasonable?  Am I missing some other mechanism to set
the default radio power level in software?

Thanks in advance for your assistance.

Andy