Buffer selection - lowest power modes

[aamirali641989]

Posted on May 23, 2014 at 13:20

I am using STM32F205RBT6 & have to make it battery operated . So lowest power consumption is desired.

What should be setting for:

1. Prefetch buffer :   I have turned off

2. Instruction cache :   I have turned off

3. Data Cache :   I have turned off

#battery-life

[waclawek.jan]

Posted on May 23, 2014 at 17:26

This does not necessarily lead to minimum *energy* consumed.

While the chip draws less current, it takes longer to complete a needed task...

JW

[jpeacock2399]

Posted on May 23, 2014 at 21:27

When running from a battery high current for a short period is not necessarily better than low current for a longer period.  Jack Gannsle in his column at embedded.com has been doing some interesting work on how best to use a battery for extended lifetime.  Peak current draw is as much a factor as watt hours consumed in battery lifetime, so running slow may be a better option to keep going as the battery nears the lower end of output voltage.

Look at the datasheet to determine the optimum system clock frequency that will fit within the max time needed to accomplish the wakeup task.  The lower the current draw the longer the battery will supply the minimum voltage needed to run.

  Jack Peacock

[chen]

Posted on May 24, 2014 at 16:08

''What should be setting for:

1. Prefetch buffer :   I have turned off

2. Instruction cache :   I have turned off

3. Data Cache :   I have turned off''

''This does not necessarily lead to minimum *energy* consumed.''

This appnote :

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/application_note/DM00096220.pdf

Says it can save power but looking at what it say - not much compared with sleep mode and clock gating/slowing. Although the app note is for the STM32F4 series, the same principles should apply for the F2 series

[waclawek.jan]

Posted on May 24, 2014 at 16:14

Interestingly enough, the 'F40x datasheet says otherwise - consumption with ART OFF is indicated to be higher...

JW