Real Low power

[stevasway]

Hi all,
I'm trying to develop an application using SMAC and low power features of MC13192 and
HCS08, but I have some problems, because my code hangs up.
I'm using RTI (1 sec) + Hibernate + STOP3 (_asm stop), and low power while for HCS08 _asm wait.

Does anyone have some suggestion, or example source code?

Does anyone have SMAC porting of PWRLIB for 802.15.4?, something else?

Thanks
Stevasway

[kbu]

attached are two screenshots from a scope datalogger thats connected across a 10ohm shunt at VIN to my circuit. (i.e. 1 Y-div = 5 mA)

can someone please comment on the graphs and let me know if the profile you see there seem to match the annotations (and code)?


DEEPSLEEP MODE :

UseMcuClock(); // MCU internal clock selected since we'll lose our external clock

PWRLib_ClockSetup(SelfClk_2MHz);

SPMSC1 = cSPMSC1Init_LVD_Disable; // disable LVD

MC13192ContReset(); // Place the MC13192 into Reset mode

PWR_HandleDeepSleep(STOP3_MODE, 5);

RadioInit();
AppInit();

// Restart to external clock appx. 10.8mS
MC13192Restart(); // Bring the MC13192 into the desired Idle condition.
MC13192Init();
MLMESetChannelRequest(2);
MLMESetMC13192ClockRate(0); // Set initial Clk speed

UseExternalClock();


- Also why is there so much fluctuation in the consumption between 2 RTI IRQs?

Message Edited by kbu on 2006-10-3104:27 PM

[bigmac]

Hello kbu,

Looking at your Sleep Power Profile plot, it is suggestive that you have a superimposed hum component, although the frequency seems a little low for 50/60 Hz hum pickup.  Is there anything in your code that cycles at about 16 Hz?  I might suggest that you increase the resistor value to, say 100 ohms, and also place a schottky diode across the resistor to limit the voltage drop during transmit.  Then see if the waveform still remains consistent with your current observations.

Can I assume that one side of the resistor is "grounded", and that you are not attempting a differential voltage measurement with the resistor in the positive supply lead?

The higher frequency "noise" component seems to indicate that there is still clock activity somewhere.

Regards,

Mac

Message Edited by bigmac on 2006-11-0101:19 PM

[kbu]

hi bigmac,

I am actually doing a differential measurement, with a resistor in series with V+.
does that mess up the results?

[bigmac]

Hello kbu,

For millivolt level signals, the differential measurement would mean that you would be more susceptable to pick up of extraraneous hum and noise during the measurement.  This would be especially so if the common mode (power supply) noise was much greater than the signal you were attempting to measure, and the differential measurement was not precisely balanced.

I would suggest that you place the low value resistor in the negative side, and use a ground-referenced measurement, to see if the results are significantly different.  Provided the voltage drop is small, hopefully the degredation of supply regulation won't affect the operation of the MCU too much.  You may still need to connect a schottky diode across the resistor, to cater for the much larger transmit current.

Regards,

Mac

[kbu]

hi bigmac,
any chance for a rough diagram explaining the connection you were talking about?