Hello If I set the MCU clock to run off 32kHz crystal and set up a 3 channel ADC sequence data collection:- 1.) How do I determine the sampling rate? 2.) Varying the extended sampling time should affect the overal sampling rate as well right? Thanks Jay
Determining the ADC sampling rate
Started by ●August 19, 2005
Reply by ●August 19, 20052005-08-19
There are two factors involved, however you clock the ADC12. These are
conversion time and sample time. tye conversion time is fixed, and you
get to vary the sample time in the ADC12CTL0 register. The conversion
time per channel is the sample time set in ADC12CTL0 SHTx bits. plus a
half cycle for tsync plus 13 cycles for conversion. Where the cycles are
based on ADC12CLK. If this is equal to 32khz then 3 channels will take
40.5 cycles plus 3 x SHTx. if this value is 4, for example the 3
conversions will take 52.5 cycles total.
Al
hc08jb8 wrote:
>Hello
>
>If I set the MCU clock to run off 32kHz crystal and set up a 3 channel
>ADC sequence data collection:-
>
>1.) How do I determine the sampling rate?
>2.) Varying the extended sampling time should affect the overal
>sampling rate as well right?
>
>Thanks
>Jay
>
>
>
>
>
>.
>
>
>Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
Reply by ●August 19, 20052005-08-19
Thanks Al for the clear explaination :-) Another quick question:- 1.) "The ADC12OSC, generated internally, is in the 5-MHz range, but varies with individual devices, supply voltage, and temperature" Does this ADC12OSC operate independant of any clock/crystal on the circuitry, i.e. when does this clock become active? when an ADC module is enabled or only when a conversion is started? Regds Jay --- In msp430@msp4..., Onestone <onestone@b...> wrote: > There are two factors involved, however you clock the ADC12. These are > conversion time and sample time. tye conversion time is fixed, and you > get to vary the sample time in the ADC12CTL0 register. The conversion > time per channel is the sample time set in ADC12CTL0 SHTx bits. plus a > half cycle for tsync plus 13 cycles for conversion. Where the cycles are > based on ADC12CLK. If this is equal to 32khz then 3 channels will take > 40.5 cycles plus 3 x SHTx. if this value is 4, for example the 3 > conversions will take 52.5 cycles total. > > Al > > hc08jb8 wrote: > > >Hello > > > >If I set the MCU clock to run off 32kHz crystal and set up a 3 channel > >ADC sequence data collection:- > > > >1.) How do I determine the sampling rate? > >2.) Varying the extended sampling time should affect the overal > >sampling rate as well right? > > > >Thanks > >Jay > > > > > > > > > > > >. > > > > > >Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > >
Reply by ●August 19, 20052005-08-19
It becomes enabled with the ADCON bit IIRC. If you want precise sampling
rates I would use the timer triggered modes of the ADC.
cheers
Al
hc08jb8 wrote:
>Thanks Al for the clear explaination :-)
>
>Another quick question:-
>1.) "The ADC12OSC, generated internally, is in the 5-MHz range, but
>varies with
>individual devices, supply voltage, and temperature" Does this
>ADC12OSC operate independant of any clock/crystal on the circuitry,
>i.e. when does this clock become active? when an ADC module is
>enabled or only when a conversion is started?
>
>Regds
>Jay
>
>
>--- In msp430@msp4..., Onestone <onestone@b...> wrote:
>
>
>>There are two factors involved, however you clock the ADC12. These
>>
>>
>are
>
>
>>conversion time and sample time. tye conversion time is fixed, and
>>
>>
>you
>
>
>>get to vary the sample time in the ADC12CTL0 register. The
>>
>>
>conversion
>
>
>>time per channel is the sample time set in ADC12CTL0 SHTx bits.
>>
>>
>plus a
>
>
>>half cycle for tsync plus 13 cycles for conversion. Where the
>>
>>
>cycles are
>
>
>>based on ADC12CLK. If this is equal to 32khz then 3 channels will
>>
>>
>take
>
>
>>40.5 cycles plus 3 x SHTx. if this value is 4, for example the 3
>>conversions will take 52.5 cycles total.
>>
>>Al
>>
>>hc08jb8 wrote:
>>
>>
>>
>>>Hello
>>>
>>>If I set the MCU clock to run off 32kHz crystal and set up a 3
>>>
>>>
>channel
>
>
>>>ADC sequence data collection:-
>>>
>>>1.) How do I determine the sampling rate?
>>>2.) Varying the extended sampling time should affect the overal
>>>sampling rate as well right?
>>>
>>>Thanks
>>>Jay
>>>
>>>
>>>
>>>
>>>
>>>.
>>>
>>>
>>>Yahoo! Groups Links
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>
>
>
>
>
>
>.
>
>
>Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>