From cafcb0508ff2a2a0b7402e23d66422393aa3bda8 Mon Sep 17 00:00:00 2001 From: Michal Lenc Date: Mon, 12 Jul 2021 18:35:46 +0200 Subject: [PATCH] Documentation/platforms/arm/imxrt: added information regarding tickless mode support Signed-off-by: Michal Lenc --- .../arm/imxrt/boards/teensy-4.x/index.rst | 14 ++++++++++++++ Documentation/platforms/arm/imxrt/index.rst | 15 +++++++++++++++ 2 files changed, 29 insertions(+) diff --git a/Documentation/platforms/arm/imxrt/boards/teensy-4.x/index.rst b/Documentation/platforms/arm/imxrt/boards/teensy-4.x/index.rst index d3dcb1b3c42..2f0fd8eceb4 100644 --- a/Documentation/platforms/arm/imxrt/boards/teensy-4.x/index.rst +++ b/Documentation/platforms/arm/imxrt/boards/teensy-4.x/index.rst @@ -118,6 +118,20 @@ focused on network-related testing. This configuration cannot be changed to Teensy 4.0 as this board does not have Ethernet capability. +pikron-bb +--------- + +This is a configuration that compiles the NuttX for use with +open source/hardware `Base Board for Teensy 4.1 +`_. +It includes CAN drivers, communication over serial port, Ethernet +support, support for 240 x 320 pixels LCD display and configuration +options for using NuttX with pysimCoder. NuttX also runs in +tickless mode with the resolution 10 usec. + +This configuration cannot be changed to Teensy 4.0 as base board +is not designed for that. + pwm-4.1 ------- diff --git a/Documentation/platforms/arm/imxrt/index.rst b/Documentation/platforms/arm/imxrt/index.rst index 95381f5ee6b..be6e4ea26ef 100644 --- a/Documentation/platforms/arm/imxrt/index.rst +++ b/Documentation/platforms/arm/imxrt/index.rst @@ -33,6 +33,21 @@ set as write-through but can be changed to write-back via Kconfig. While write-b performance than write-through, it is not supported for all peripherals in NuttX yet. Write-back data cache can not be selected while running Ethernet or serial port over USB. +Tickless OS +=========== + +With Tickless OS, the periodic, timer interrupt is eliminated and replaced with a one-shot, +interval timer, that becomes event driven instead of polled. This allows to run the MCU with +higher resolution without using more of the CPU bandwidth processing useless interrupts. + +Only tickless via an alarm is currently supported for i.MX RT MCU, which can be selected by +CONFIG_SCHED_TICKLESS_ALARM option. CONFIG_USEC_PER_TICK option determines the resolution +of time reported by :c:func:`clock_systime_ticks()` and the resolution of times that can be set +for certain delays including watchdog timers and delayed work. It is important that value set in +CONFIG_USEC_PER_TICK represents the frequency of GPT timer that runs the tickless mode. Clock +source of the timer is 16.6 MHz, which is then devided by the prescaler value from 1 to 4096. +Possible values for CONFIG_USEC_PER_TICK are 10 or 100 for example. + Peripheral Support ==================