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Gregory Nutt 2015-12-02 18:54:17 -06:00
parent 216f762e56
commit f04287305d
5 changed files with 82 additions and 0 deletions
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14
configs/sama5d3-xplained/README.txt
View File

@ -2530,12 +2530,26 @@ Tickless OS
CONFIG_SAMA5_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free- CONFIG_SAMA5_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free-
: running timer : running timer
The resolution of the clock is provided by the CONFIG_USEC_PER_TICK
setting in the configuration file.
NOTE: In most cases, the slow clock will be used as the timer/counter NOTE: In most cases, the slow clock will be used as the timer/counter
input. You should enable the 32.768KHz crystal for the slow clock by input. You should enable the 32.768KHz crystal for the slow clock by
calling sam_sckc_enable(). Otherwise, you will be doing all system calling sam_sckc_enable(). Otherwise, you will be doing all system
timing using the RC clock! UPDATE: This will now be selected by default timing using the RC clock! UPDATE: This will now be selected by default
when you configure for TICKLESS support. when you configure for TICKLESS support.
The slow clock has a resolution of about 30.518 microseconds. Ideally, the
value of CONFIG_USEC_PER_TICK should be an exact multiple of the clock
resolution. Otherwise there will be cumulative timing inaccuracies. A
choice of:
CONFIG_USEC_PER_TICK=61, or
CONFIG_USEC_PER_TICK=122
will be close but will still have inaccuracies that will effect the time
due to long term error build-up.
SAMA5 Timer Usage SAMA5 Timer Usage
----------------- -----------------
This current implementation uses two timers: A one-shot timer to This current implementation uses two timers: A one-shot timer to

14
configs/sama5d3x-ek/README.txt
View File

@ -2850,12 +2850,26 @@ Tickless OS
CONFIG_SAMA5_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free- CONFIG_SAMA5_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free-
: running timer : running timer
The resolution of the clock is provided by the CONFIG_USEC_PER_TICK
setting in the configuration file.
NOTE: In most cases, the slow clock will be used as the timer/counter NOTE: In most cases, the slow clock will be used as the timer/counter
input. You should enable the 32.768KHz crystal for the slow clock by input. You should enable the 32.768KHz crystal for the slow clock by
calling sam_sckc_enable(). Otherwise, you will be doing all system calling sam_sckc_enable(). Otherwise, you will be doing all system
timing using the RC clock! UPDATE: This will now be selected by default timing using the RC clock! UPDATE: This will now be selected by default
when you configure for TICKLESS support. when you configure for TICKLESS support.
The slow clock has a resolution of about 30.518 microseconds. Ideally, the
value of CONFIG_USEC_PER_TICK should be an exact multiple of the clock
resolution. Otherwise there will be cumulative timing inaccuracies. A
choice of:
CONFIG_USEC_PER_TICK=61, or
CONFIG_USEC_PER_TICK=122
will be close but will still have inaccuracies that will effect the time
due to long term error build-up.
SAMA5 Timer Usage SAMA5 Timer Usage
----------------- -----------------
This current implementation uses two timers: A one-shot timer to This current implementation uses two timers: A one-shot timer to

14
configs/sama5d4-ek/README.txt
View File

@ -3358,12 +3358,26 @@ Tickless OS
CONFIG_SAMA5_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free- CONFIG_SAMA5_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free-
: running timer : running timer
The resolution of the clock is provided by the CONFIG_USEC_PER_TICK
setting in the configuration file.
NOTE: In most cases, the slow clock will be used as the timer/counter NOTE: In most cases, the slow clock will be used as the timer/counter
input. You should enable the 32.768KHz crystal for the slow clock by input. You should enable the 32.768KHz crystal for the slow clock by
calling sam_sckc_enable(). Otherwise, you will be doing all system calling sam_sckc_enable(). Otherwise, you will be doing all system
timing using the RC clock! UPDATE: This will now be selected by default timing using the RC clock! UPDATE: This will now be selected by default
when you configure for TICKLESS support. when you configure for TICKLESS support.
The slow clock has a resolution of about 30.518 microseconds. Ideally, the
value of CONFIG_USEC_PER_TICK should be an exact multiple of the clock
resolution. Otherwise there will be cumulative timing inaccuracies. A
choice of:
CONFIG_USEC_PER_TICK=61, or
CONFIG_USEC_PER_TICK=122
will be close but will still have inaccuracies that will effect the time
due to long term error build-up.
UPDATE: As of this writing (2014-8-11), the Tickless support is UPDATE: As of this writing (2014-8-11), the Tickless support is
functional. However, the timing for all delays appears to be half the functional. However, the timing for all delays appears to be half the
duration that it should be. I don't see anything wrong with the setup duration that it should be. I don't see anything wrong with the setup

20
configs/same70-xplained/README.txt
View File

@ -898,6 +898,9 @@ Tickless OS
CONFIG_SAMV7_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free- CONFIG_SAMV7_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free-
: running timer : running timer
The resolution of the clock is provided by the CONFIG_USEC_PER_TICK
setting in the configuration file.
NOTE: In most cases, the slow clock will be used as the timer/counter NOTE: In most cases, the slow clock will be used as the timer/counter
input. The SAME70-Xplained board has pads for a 32.768KHz crystal, input. The SAME70-Xplained board has pads for a 32.768KHz crystal,
however, the boad ships with that position unpopulated. So, be default however, the boad ships with that position unpopulated. So, be default
@ -908,6 +911,23 @@ Tickless OS
definition BOARD_HAVE_SLOWXTAL in the configs/same70-xplained/board.h definition BOARD_HAVE_SLOWXTAL in the configs/same70-xplained/board.h
file. file.
The slow clock has a resolution of about 30.518 microseconds. Ideally, the
value of CONFIG_USEC_PER_TICK should be an exact multiple of the clock
resolution. Otherwise there will be cumulative timing inaccuracies. A
choice of:
CONFIG_USEC_PER_TICK=61, or
CONFIG_USEC_PER_TICK=122
will be close but will still have inaccuracies that will effect the time
due to long term error build-up.
UPDATE: As of this writing (2015-12-02), the Tickless support is
functional. However, the timing for all delays appears to be half the
duration that it should be. I don't see anything wrong with the setup
and I am suspecting that there may be something I don't understand about
the counting frequency.
SAME70 Timer Usage SAME70 Timer Usage
------------------ ------------------
This current implementation uses two timers: A one-shot timer to This current implementation uses two timers: A one-shot timer to

20
configs/samv71-xult/README.txt
View File

@ -1489,10 +1489,30 @@ Tickless OS
CONFIG_SAMV7_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free- CONFIG_SAMV7_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free-
: running timer : running timer
The resolution of the clock is provided by the CONFIG_USEC_PER_TICK
setting in the configuration file.
NOTE: In most cases, the slow clock will be used as the timer/counter NOTE: In most cases, the slow clock will be used as the timer/counter
input. The 32.768KHz crystal is selected by the definition input. The 32.768KHz crystal is selected by the definition
BOARD_HAVE_SLOWXTAL in the configs/samv71-xult/board.h file. BOARD_HAVE_SLOWXTAL in the configs/samv71-xult/board.h file.
The slow clock has a resolution of about 30.518 microseconds. Ideally, the
value of CONFIG_USEC_PER_TICK should be an exact multiple of the clock
resolution. Otherwise there will be cumulative timing inaccuracies. A
choice of:
CONFIG_USEC_PER_TICK=61, or
CONFIG_USEC_PER_TICK=122
will be close but will still have inaccuracies that will effect the time
due to long term error build-up.
UPDATE: As of this writing (2015-12-02), the Tickless support is
functional. However, the timing for all delays appears to be half the
duration that it should be. I don't see anything wrong with the setup
and I am suspecting that there may be something I don't understand about
the counting frequency.
SAMV7 Timer Usage SAMV7 Timer Usage
----------------- -----------------
This current implementation uses two timers: A one-shot timer to This current implementation uses two timers: A one-shot timer to