[Tinyos-host-mote-wg] [Tinyos-2.0wg] Meeting 8/31

[Philip Levis]

Wednesday, August 31, 2005 11:00 AM US Pacific Time  Where: 8-356-2663,
916-356-2663, Bridge: 1, Passcode: 3967115

1-888-875-9370 (US non-intel employees)
0-800-1000-104 (Germany)

Agenda:

1) Pre2 release cheer (hopefully)
2) Try to write a paper for NSDI?
3) Status: serial stack, CC2420/micaZ, etc.
4) Power management discussion

Is there anything else people would like to discuss?

This is the message I sent out to the power management subgroup (did  
I miss someone? some part of me thinks Vlado might have been in the  
subgroup? I forget):

*****************

From:       pal at eecs.berkeley.edu
Subject:     2.x power management
Date:     August 28, 2005 5:13:59 PM PDT
To:       rob at moteiv.com, mturon at xbow.com, lama.nachman at intel.com,  
culler at eecs.berkeley.edu

The current proposal on the table involves a hybrid solution, where  
the platform computes its best guess at a low power state based on  
hardware configuration, but components can override this with a  
'latency' specification. I think that there's no reason we can't  
unify these two, where the latency specification is merely an input  
to the platform (another piece of state it considers).

This means that, the power state of the MCU is implicit, based on the  
power state of all of the peripherals and the specified maximum  
wakeup latency. So, you'd see something like this:

RadioControl.off();
TempControl.off();
StorageControl.off();
LatencyControl.maxWakeup(1000); // I'm guessing us is the parameter,  
so 1 ms here

Then the platform does something like it does today:

inline void TOSH_sleep() {
   // The LPM we can go down to depends on the clocks used. We never go
   // below LPM3, so ACLK is always enabled, also TimerB clock source
   // is assumed to be ACLK.
   // We check MSP430's TimerA, USART0/1, ADC12 peripheral modules if  
they
   // use MCLK or SMCLK and switch to the lowest LPM that keeps
   // the required clock(s) running.
   extern uint8_t TOSH_sched_full;
   extern volatile uint8_t TOSH_sched_free;
   __nesc_atomic_t fInterruptFlags;
   uint16_t LPMode_bits = 0;

   fInterruptFlags = __nesc_atomic_start();

   if ((LPMode_disabled) || (TOSH_sched_full != TOSH_sched_free)) {
     __nesc_atomic_end(fInterruptFlags);
     return;
   } else {
     LPMode_bits = LPM3_bits;
     // TimerA, USART0, USART1 check
     if ( (((TACCTL0 & CCIE) || (TACCTL1 & CCIE) || (TACCTL2 & CCIE))
          && ((TACTL & TASSEL_3) == TASSEL_2))
       || ((ME1 & (UTXE0 | URXE0)) && (U0TCTL & SSEL1))
       || ((ME2 & (UTXE1 | URXE1)) && (U1TCTL & SSEL1))
#ifdef __msp430_have_usart0_with_i2c
       // registers end in "nr" to prevent nesC race condition detection
       || ((U0CTLnr & I2CEN) && (I2CTCTLnr & SSEL1) &&
           (I2CDCTLnr & I2CBUSY) && (U0CTLnr & SYNC) && (U0CTLnr & I2C))
#endif
       )
       LPMode_bits = LPM1_bits;
#ifdef __msp430_have_adc12
     // ADC12 check
     if (ADC12CTL1 & ADC12BUSY){
       if (!(ADC12CTL0 & MSC) && ((TACTL & TASSEL_3) == TASSEL_2))
          LPMode_bits = LPM1_bits; // TimerA for ADC12
       else
         switch (ADC12CTL1 & ADC12SSEL_3){
           case ADC12SSEL_2: LPMode_bits = 0; break;
           case ADC12SSEL_3: LPMode_bits = LPM1_bits; break;
         }
     }
#endif
     LPMode_bits |= SR_GIE;
     __asm__ __volatile__( "bis  %0, r2" : : "m" ((uint16_t) 
LPMode_bits) );
   }
}

with some additional conditions to make sure it doesn't go beyond the  
latency.

This is the HIL layer: there can certainly be HAL abstractions that  
provide more fine grained control, but they are understandably  
hardware-specific. With these mechanisms, one can create higher-level  
policies. E.g., a service distribution could have a component  
SensorPower, which with a single call to StdControl turns on/off ALL  
of the sensors in the system.

What are people's opinions on this approach?
******

Phil

-------

"We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time."

- T. S. Eliot,  'Little Gidding'




Phil

-------

"We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time."

- T. S. Eliot,  'Little Gidding'

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