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| author | Gregory Nutt <gnutt@nuttx.org> | 2014-08-10 13:11:31 -0600 |
|---|---|---|
| committer | Gregory Nutt <gnutt@nuttx.org> | 2014-08-10 13:11:31 -0600 |
| commit | f73988dd9b1e4c6ae096871b1f98024827b2f82b (patch) | |
| tree | dece4595d00fe6bbba94f165ea7253c9ad638a52 /nuttx/configs/sama5d4-ek/README.txt | |
| parent | 8d3575ca890cd84fba197e21d96e9e60fd965b8e (diff) | |
| download | px4-nuttx-f73988dd9b1e4c6ae096871b1f98024827b2f82b.tar.gz px4-nuttx-f73988dd9b1e4c6ae096871b1f98024827b2f82b.tar.bz2 px4-nuttx-f73988dd9b1e4c6ae096871b1f98024827b2f82b.zip | |
Cosmetic changed, updated README files, improved comments
Diffstat (limited to 'nuttx/configs/sama5d4-ek/README.txt')
| -rw-r--r-- | nuttx/configs/sama5d4-ek/README.txt | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/nuttx/configs/sama5d4-ek/README.txt b/nuttx/configs/sama5d4-ek/README.txt index 7d0cb70ba..a2c81e53c 100644 --- a/nuttx/configs/sama5d4-ek/README.txt +++ b/nuttx/configs/sama5d4-ek/README.txt @@ -3112,6 +3112,8 @@ TM7000 LCD/Touchscreen Tickless OS =========== + Background + ---------- By default, a NuttX configuration uses a periodic timer interrupt that drives all system timing. The timer is provided by architecture-specifi code that calls into NuttX at a rate controlled by CONFIG_USEC_PER_TICK. @@ -3148,6 +3150,8 @@ Tickless OS OS event will occur, program the interval time and wait for it to fire. When the interval time fires, then the scheduled activity is performed. + Configuration + ------------- The following configuration options will enable support for the Tickless OS for the SAMA5D platforms using TC0 channels 0-3 (other timers or timer channels could be used making the obvious substitutions): @@ -3165,6 +3169,25 @@ Tickless OS CONFIG_SAMA5_TICKLESS_FREERUN=1 : Selects TC0 channel 1 for the free- : running timer + SAMA5 Timer Usage + ----------------- + This current implementation uses two timers: A one-shot timer to + provide the timed events and a free running timer to provide the current + time. Since timers are a limited resource, that could be an issue on + some systems. + + We could do the job with a single timer if we were to keep the single + timer in a free-running at all times. The SAMA5 timer/counters have + 32-bit counters with the capability to generate a compare interrupt when + the timer matches a compare value but also to continue counting without + stopping (giving another, different interrupt when the timer rolls over + from 0xffffffff to zero). So we could potentially just set the compare + at the number of ticks you want PLUS the current value of timer. Then + you could have both with a single timer: An interval timer and a free- + running counter with the same timer! + + Patches are welcome! + SAMA4D4-EK Configuration Options ================================= |