Commit Graph

3 Commits

Author SHA1 Message Date
robert-hh 81f706aee4 mimxrt: Support PWM using the FLEXPWM and QTMR modules.
Frequency range 15Hz/18Hz to > 1 MHz, with decreasing resolution of the
duty cycle.  The basic API is supported as documentated, except that
keyword parameters are accepted for both the instatiaton and the
PWM.init() call.

Extensions: support PWM for channel pairs.  Channel pairs are declared by
supplying 2-element tuples for the pins.  The two channels of a pair must
be the A/B channel of a FLEXPWM module.  These form than a complementary
pair.

Additional supported keyword arguments:

- center=value Defines the center position of a pulse within the pulse
  cycle.  The align keyword is actually shortcut for center.

- sync=True|False: If set to True, the channels will be synchronized to a
  submodule 0 channel, which has already to be enabled.

- align=PWM.MIDDLE | PMW.BEGIN | PWM.END. It defines, whether synchronized
  channels are Center-Aligned or Edge-aligned.  The channels must be either
  complementary a channel pair or a group of synchronized channels.  It may
  as well be applied to a single channel, but withiout any benefit.

- invert= 0..3. Controls ouput inversion of the pins.  Bit 0 controls the
  first pin, bit 1 the second.

- deadtime=time_ns time of complementary channels for delaying the rising
  slope.

- xor=0|1|2 xor causes the output of channel A and B to be xored.  If
  applied to a X channel, it shows the value oif A ^ B.  If applied to an A
  or B channel, both channel show the xored signal for xor=1.  For xor=2,
  the xored signal is split between channels A and B.  See also the
  Reference Manual, chapter about double pulses.  The behavior of xor=2 can
  also be achieved using the center method for locating a pulse within a
  clock period.

The output is enabled for board pins only.

CPU pins may still be used for FLEXPWM, e.g. as sync source, but the signal
will not be routed to the output.  That applies only to FLEXPWM pins.  The
use of QTMR pins which are not board pins will be rejected.

As part of this commit, the _WFE() statement is removed from
ticks_delay_us64() to prevent PWM glitching during calls to sleep().
2021-11-24 13:48:27 +11:00
robert-hh 99221cd118 mimxrt: Fix cycle counter for time.ticks_cpu() and machine.bitstream().
Prior to this commit mp_hal_ticks_cpu() was not started properly.  It only
started when the code was executed with a debugger attached, except for the
Teensy (i.MXRT1062) boards.  As an additional fix, the CYYCNT timer is now
started at boot time.

Also rename mp_hal_ticks_cpu_init() to mp_hal_ticks_cpu_enable().
2021-10-25 15:50:44 +11:00
Damien George 7408ca1d78 mimxrt: Improve ticks and sleep functions using GPT.
SysTick cannot wake the CPU from WFI/WFE so a hardware timer is needed to
keep track of ticks/delay (similar to the nrf port).

Fixes issue #7234.

Signed-off-by: Damien George <damien@micropython.org>
2021-05-18 22:36:32 +10:00