This adds a wlan.config(reconnects=N) option to set the number of reconnect
attempts that will be made if the WLAN connection goes down. The default
is N=-1 (infinite retries, current behavior). Setting
wlan.config(reconnects=0) will disable the reconnect attempts.
A nice side effect of reconnects=0 is that wlan.status() will report the
disconnect reason now. See related issue #5326.
Ethernet-PHYs from ESP-IDF (LAN8720, IP101, RTL8201, DP83848) are now
supported in IDF v4.1 and above. PHY_KSZ8041 is only for ESP-IDF 4.3 and
above. ESP32S2 is not supported.
Signed-off-by: Tobias Eydam <eydam-prototyping@outlook.com>
The implementation uses the LPUARTx devices. Up to 8 UARTs can be used,
given that the pins are accessible. E.g. 8 on Teensy 4.1, 5 on
MIMXRT1020_EVK.
For Tennsy 4.0 and 4.1 the UART numbers are as printed on the pinout 1..N.
The MIMXRT10xx-EVK boards have only one UART named, which gets the number
1. All other UART are assigned to different Pins:
MIMXRT1010-EVK:
D0/D1 UART 1
D6/D7 UART 2
A0/D4 UART 3
MIMXRT1020-EVK:
D0/D1 UART 1
D6/D9 UART 2
D10/D12 UART 3
D14/D15 UART 4
A0/A1 UART 5
MIMXRT1050-EVK, MIMXRT1060-EVK, MIMXRT1064-EVK:
D0/D1 UART 1
D7/D6 UART 2
D8/D9 UART 3
A1/A0 UART 4
This fixes error: cast to smaller integer type 'int' from 'pthread_t'.
pthread_t is defined as long, not as int.
Signed-off-by: Pavol Rusnak <pavol@rusnak.io>
The rtc_set_datetime() from pico-sdk will validate the values in the
datetime_t structure and refuse to set the time if they aren't valid. It
makes sense to raise an exception if this happens instead of failing
silently which might be confusing (as an example, see:
https://github.com/micropython/micropython/pull/6928#issuecomment-860166044
).
The supplied value for microseconds in datetime() will be treated as a
starting value for the reported microseconds. Due to internal processing
in setting the time, there is an offset about 1 ms.
This change moves the datetime tuple format back to the one used by all the
other ports:
(year, month, day, weekday, hour, minute, second, microsecond)
Weekday is a number between 0 and 6, with 0 assigned to Monday. It has to
be provided when setting the RTC with datetime(), but will be ignored on
entry and calculated when needed.
The weekday() method was removed, since that is now again a part of the
datetime tuple.
The now() method was updated so it continues to return a tuple that matches
CPython's datetime module.
Initial support for machine.RTC on rp2 port. It only supports datetime()
method and nothing else. The method gets/returns a tuple of 8 items, just
like esp32 port, for example, but the usec parameter is ignored as the RP2
RTC only works up to seconds precision.
The Pico RTC isn't very useful as the time is lost during reset and there
seems to be no way to easily power up just the RTC clock with a low current
voltage, but still there seems to be use-cases for that, see issues #6831,
and a Thonny issue #1592. It was also requested for inclusion on v1.15
roadmap on #6832.
Signed-off-by: Krzysztof Adamski <k@japko.eu>
Changes introduced are:
- the application offset is now loaded from the partition table instead of
being hard-coded to 0x10000
- maximum size of all sections is computed using the partition table
- an error is generated if any section overflows its allocated space
- remaining bytes are printed for each section
Signed-off-by: Damien George <damien@micropython.org>
This commit adds a few math functions to the source list in the Makefile,
and implements the log2f function, so that ulab can be compiled on the nrf
boards. It also addresses part of #5162.
This commit fixes the following problems converting to/from Python integers
and ffi types:
- integers of 8 and 16 bits not working on big endian
- integers of 64 bits not working on 32 bits architectures
- unsigned returns were converted to signed Python integers
Fixes issue #7269.
Currently only advertising and scanning are supported, using the ring
buffer for events (ie not synchronous events at this stage).
The ble_gap_advertise.py multi-test passes (tested on a nucleo_wb55rg
board).
Signed-off-by: Damien George <damien@micropython.org>
Zephyr's default value for CONFIG_NET_SOCKETS_POSIX_NAMES was changed
from false to true between Zephyr v2.5.0 and v2.6.0. This caused
conflicts in MicroPython, which uses the zsock_ prefixed functions, so
disable it.
Signed-off-by: Maureen Helm <maureen.helm@nxp.com>
Zephyr's Kconfig symbols and defaults for SDHC/SDMMC disk drivers and
the disk access subsystem were reworked between Zephyr v2.5.0 and
v2.6.0. Update MicroPython accordingly.
Signed-off-by: Maureen Helm <maureen.helm@nxp.com>
Initial version, using the LP RTC clock. It provides setting the date and
time with rtc.init() or rtc.datetime(), and reading the date and time with
rtc.datetime() or rtc.now(). The method weekday() reports the weekday of
the current date. It starts with 0 for Monday.
The tuple order for datetime() and now() matches the CPython sequence:
(year, month, day, hour, minute, second, microsecond, TZ). TZ is ignored
and reported as None. Microsecond is provided at a best effort.
If a battery is not supplied, the default boot date/time is 1970/1/1 0:0:0.
With a battery, the clock continues to run even when the board is not
powered. The clock is quite precise. If not, using rtc.calibration() may
help.
It supports three hardware timer channels based on the PIT timers of the
MIMXRT MCU. The timer id's are 0, 1 and 2. On soft reboot all active
timers will be stopped via finalisers.
This is required since the Teensy Halfkay loader attempts to erase all of
the flash but fails to do so, at least in my tests. Formatting brings it
back to a known state.
This commit adds full support for a filesystem on all boards, with a block
device object mimxrt.Flash() and uos.VfsLfs2 enabled.
Main changes are:
- Refactoring of linker scripts to accomodate reserved area for VFS. VFS
will take up most of the available flash. 1M is reserved for code. 9K is
reserved for flash configuration, interrupts, etc.
- Addition of _boot.py with filesystem init code, called from main.c.
- Definition of the mimxrt module with a Flash class in modmimxrt.[ch].
- Implementation of a flash driver class in mimxrt_flash.c. All flashing
related functions are stored in ITCM RAM.
- Addition of the uos module with filesystem functions.
- Implementation of uos.urandom() for the sake of completeness of the uos
module.
It uses sample code from CircuitPython supplied under MIT license, which
uses the NXP SDK example code.
Done in collaboration with Philipp Ebensberger aka @alphaFred who
contributed the essential part to enable writing to flash while code is
executing, among other things.
Adds support for NeoPixels on GPIO32 and GPIO33 on ESP32. Otherwise,
NeoPixels wired to GPIO32/33 wll silently fail without any hints to the
user.
With thanks to @robert-hh.
Fixes issue #7221.
ATOM is a very small ESP32 development board produced by M5Stack, with a
size of 24mm * 24mm, with peripherals such as WS2812, IR, button, MPU6886
(Only Matrix), and 8 GPIO extensions. It also has a plastic shell.
With GCC 11 there is now a warning about array bounds of OTP-mac, due to
the OTP being a literal address.
Signed-off-by: Damien George <damien@micropython.org>
The 512k build does not have a filesystem so there is no reason to include
the filesystem-related modules. This commit provides a custom manifest.py
for this board which no longer includes: _boot.py, flashbdev.py,
inisetup.py, upip.py, upip_utarfile.py. This cuts the build down by about
9k of flash.
Signed-off-by: Damien George <damien@micropython.org>
- modified pin type from pin_obj_t to machine_pin_obj_t
- created machine_pin.c
- implemented basic version of make-pins.py to genertate pins.c/.h files
automatically; the only alternate function currently supported is GPIO
- added af.csv files for all supported MCUs
- replaced pins.c/pins.h files with pin.csv for all boards
- implemented on/off/high/low/value/init methods
- Implemented IN/OUT/OPEN_DRAIN modes
- modified LDFLAGS for DEBUG build to get usefull .elf file for debugging
Signed-off-by: Philipp Ebensberger
Leaving the bootloader from an IRQ (eg USB or I2C IRQ) will not work if
MBOOT_LEAVE_BOOTLOADER_VIA_RESET is disabled, ie if mboot jumps directly to
the application. This is because the CPU will still be in IRQ state when
the application starts and IRQs of lower priority will be blocked.
Fix this by setting a flag when the bootloader should finish, and exit the
bootloader always from the main (top level) thread.
This also improves the USB behaviour of mboot: it no longer abruptly
disconnects when the manifest command is sent.
Signed-off-by: Damien George <damien@micropython.org>
RX and CTS are the input pins and pull-ups are enabled so they don't cause
a problem if left unconnected. But the output pins don't need a pull up
(they were originally all configured with pull up in commit
8f7491a109).
If needed, the pull-ups can be disabled in Python using machine.Pin after
the UART is constructed.
See issue #4369.
Signed-off-by: Damien George <damien@micropython.org>
The DMA driver will turn off DMA if it hasn't been used for an amount of
time (to save power). The SDIO driver for cyw43 WLAN was not informing the
DMA driver that it was using DMA and there was a chance that the DMA would
turn off in the middle of an SDIO DMA transfer. The symptoms of this would
be printing of SDIO error messages and a failure to communicate with the
cyw43 WLAN module.
This commit fixes this issue by changing the SDIO driver to use the
dma_nohal_XXX API to initialise and start the DMA.
Signed-off-by: Damien George <damien@micropython.org>
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>
A board can now customise mboot with:
- MBOOT_LED1, MBOOT_LED2, MBOOT_LED3, MBOOT_LED4: if it needs to have
different LEDs for mboot compared to the application
- MBOOT_BOARD_LED_INIT: if it needs a fully customised LED init function
- MBOOT_BOARD_LED_STATE: if it needs a fully customised LED state-setting
function
- MBOOT_BOARD_GET_RESET_MODE: if it needs a fully customised function to
get the reset mode
With full customisation, the only requirement is a single LED to show the
status of the bootloader (idle, erasing, flashing, etc), which can be
configured to do nothing if needed.
Signed-off-by: Damien George <damien@micropython.org>
It is enabled by default to get the standard behaviour of doing a reset
after it is finished, but can be disabled by a board to jump straight to
the application (likely the board needs to use MBOOT_BOARD_CLEANUP to make
this work).
The application is passed a reset mode of BOARDCTRL_RESET_MODE_BOOTLOADER
if the bootloader was active and entered via a jump.
Signed-off-by: Damien George <damien@micropython.org>
This new logic is equivalent to the old logic when the only possibilities
for reset_mode are NORMAL, SAFE_MODE and FILESYSTEM, which is the standard
case. But the new logic also allows other reset_mode values (eg
BOOTLOADER) to run boot.py and main.py.
Signed-off-by: Damien George <damien@micropython.org>
When disabled the bootloader is entered via a direct jump. When enabled
the bootloader is entered via a system reset then a jump. It's enabled by
default to retain the existing behaviour, which is the recommended way.
Signed-off-by: Damien George <damien@micropython.org>
Improvements made:
- PSRAM support for S2
- partition definition for 16MiB flash
- correct ADC and DAC pins
- correct GPIO and IRQ pins
- S3 components in CMakeLists
Based on original commit made by Seon Rozenblum aka @UnexpectedMaker.
Signed-off-by: Damien George <damien@micropython.org>
Any code running on core1 should be stopped on soft-reset (the GC heap is
reset so if code continues to run on core1 it will see corrupt memory).
Signed-off-by: Damien George <damien@micropython.org>
So a lock can be acquired on one Python thread and then released on
another. A test for this is added.
Signed-off-by: Damien George <damien@micropython.org>
Because vPortCleanUpTCB runs on the FreeRTOS idle task and cannot execute
any VM or runtime related code like freeing memory.
Signed-off-by: Damien George <damien@micropython.org>
This fixes a bug where double arguments on a 32-bit architecture would not
be passed correctly because they only had 4 bytes of storage (not 8). It
also fixes a compiler warning/error in return_ffi_value on certian
architectures: array subscript 'double[0]' is partly outside array bounds
of 'ffi_arg[1]' {aka 'long unsigned int[1]'}.
Fixes issue #7064.
Signed-off-by: Damien George <damien@micropython.org>
The number shown in the USB id is now the same as that returned by
machine.unique_id(). All 8 bytes are inserted as hex into the USB id. A
usb id at /dev/serial/by-id then looks like:
usb-MicroPython_Board_in_FS_mode_e469b03567342f37-if00
Doing "import <tab>" will now complete/list built-in modules.
Originally at adafruit#4548 and adafruit#4608
Signed-off-by: Artyom Skrobov <tyomitch@gmail.com>
This board does not work with CONFIG_NETWORKING enabled. And
CONFIG_CONSOLE_SUBSYS is enabled so that ctrl-C works.
Signed-off-by: Damien George <damien@micropython.org>
And ctrl-C can now interrupt a time.sleep call. This uses Zephyr's k_poll
API to wait efficiently for an event signal, and an optional semaphore.
Signed-off-by: Damien George <damien@micropython.org>
This helper is added to properly set a pending exception, to mirror
mp_sched_schedule(), which schedules a function.
Signed-off-by: Damien George <damien@micropython.org>
If MICROPY_ENABLE_SCHEDULER is enabled then MP_STATE_VM(sched_state) must
be updated after handling the pending exception, which is done by the
mp_handle_pending() function.
Signed-off-by: Damien George <damien@micropython.org>
This can now be selected by setting MICROPY_HW_SDIO_SDMMC, which defaults
to 1, ie SDMMC1. The pins can also be selected and default to the standard
C8/C9/C10/C11/C12/D2.
This can now be selected by setting MICROPY_HW_SDCARD_SDMMC, which defaults
to 1, ie SDMMC1. This commit also renames the SD pin configuration macros
from MICROPY_HW_SDMMC2_xxx to MICROPY_HW_SDCARD_xxx, as well as renaming
MICROPY_HW_SDMMC_BUS_WIDTH to MICROPY_HW_SDCARD_BUS_WIDTH.
Signed-off-by: Damien George <damien@micropython.org>
A board can now define MBOOT_TEXT0_ADDR to place mboot at a location other
than 0x08000000. This can be useful if, for example, there is already a
different bootloader on the device.
Signed-off-by: Damien George <damien@micropython.org>
A board can now define MBOOT_LD_FILES (at the Makefile-level) to specify
custom linker scripts. And stm32_generic.ld has been split into 2 pieces
so one or the other can be reused (usually stm32_sections.ld wolud be
reused by a board, and stm32_memory.ld redefined).
Signed-off-by: Damien George <damien@micropython.org>
A board can now use BUILDING_MBOOT at the Makefile-level to do things
conditional on building mboot, for example add source files to SRC_C.
Signed-off-by: Damien George <damien@micropython.org>
Commit 1e297c8898 introduced a bug where the
very first reset-mode state on the LEDs was not shown, because prior to
that commit the first reset-mode state was the same as the initial LED
state (green on, others off) and update_reset_mode() was called after
setting this initial LED state.
This is fixed in this commit by changing the update_reset_mode() loop so
that it displays the current reset mode before doing the delay.
Signed-off-by: Damien George <damien@micropython.org>
And use the same boardctrl.h header for both the application and mboot so
these constants are consistent.
Signed-off-by: Damien George <damien@micropython.org>
This adds support for making static (ie not on the Python GC heap) soft
timers. This can be useful for a board to define a custom background
handler, or eventually for BLE/network processing to use instead of systick
slots; it will be more efficient using soft timer for this.
The main issue with using the existing code for static soft timers is that
it would combine heap allocated and statically allocated soft_timer_entry_t
instances in the same pairing-heap data structure. This would prevent the
GC from tracing some of the heap allocated entries (because the GC won't
follow pointers outside the heap).
This commit makes it so that soft timer entries are explicitly marked,
instead of relying on implicit marking by having the root of the pairing
heap in the root pointer section. Also, on soft reset only the heap-
allocated soft timers are deleted from the pairing heap, leaving the
statically allocated ones.
Signed-off-by: Damien George <damien@micropython.org>
This commit re-enables the command-line make option "FROZEN_MANIFEST". The
boards/*/mpconfigboard.cmake will now use the command-line FROZEN_MANIFEST
value if supplied.
Usage: make FROZEN_MANIFEST=~/foo/my-manifest.py
Because "find_package(Python3 ...)" requires at least this version of
CMake. And other features like GREATER_EQUAL and COMMAND_EXPAND_LISTS need
at least CMake 3.7 and 3.8 respectively.
Signed-off-by: Damien George <damien@micropython.org>
Improvements are:
- Default period is 1000ms with callback disabled.
- if period is not specified then it's not updated (previously, if period
was not specified then it was set to -1 and running the timer callback as
fast as possible, making the REPL unresponsive).
- Use uint64_t to compute delta_ms, and raise a ValueError if the period is
too large.
- If callback is not specified then it's not updated.
- Specifying None for the callback will disable the timer.
Signed-off-by: Damien George <damien@micropython.org>
The PIO state machines on the RP2040 have 4 word deep TX and RX FIFOs. If
you only need one direction, you can "merge" them into either a single 8
word deep TX or RX FIFO.
We simply add constants to the PIO object, and set the appropriate bits in
`shiftctrl`.
Resolves#6854.
Signed-off-by: Tim Radvan <tim@tjvr.org>
Commit 8a917ad252 added the gpio_reset_pin()
call to make sure that pins that were used as ADC inputs could subsequently
be used as digital IO. But calling gpio_reset_pin() will enable the
pull-up on the pin and so pull it high for a brief period. Instead use
rtc_gpio_deinit() which will just reconfigure the pin as a digital IO and
do nothing else.
Fixes issue #7079 (see also #5771).
Signed-off-by: Damien George <damien@micropython.org>
For an unconnected TCP socket, poll should return WR|HUP and read should
raise ENOTCONN. This is implemented by this commit and now the following
tests pass on esp32: extmod/usocket_tcp_basic.py,
net_hosted/connect_poll.py.
Signed-off-by: Damien George <damien@micropython.org>
This change allows running the tests in tests/basics/ without any failures
(but some tests are still skipped).
Signed-off-by: Damien George <damien@micropython.org>
This fixes `error: variable 'subpkg_tried' might be clobbered by 'longjmp'
or 'vfork' [-Werror=clobbered]` when compiling on ppc64le and aarch64 (and
possibly other architectures/toolchains).
This function includes the UART prescaler in the calculation (if it has
one, eg on H7 and WB MCUs).
Signed-off-by: Damien George <damien@micropython.org>
The STM32WB has a problem when address resolution is enabled: under certain
conditions the MCU can get into a state where it draws an additional 10mA
or so and eventually ends up with a broken BLE RX path in the silicon. A
simple way to reproduce this is to enable address resolution (which is the
default for NimBLE) and start the device advertising. If there is enough
BLE activity in the vicinity then the device will at some point enter the
bad state and, if left long enough, will have permanent BLE RX damage.
STMicroelectronics are aware of this issue. The only known workaround at
this stage is to not enable address resolution, which is implemented by
this commit.
Work done in collaboration with Jim Mussared aka @jimmo.
Signed-off-by: Damien George <damien@micropython.org>
Prior to this commit, if C2 was busy (eg lots of BLE activity) then it may
not have had time to respond to the notification on the IPCC_CH_MM channel
by the time additional memory was available to put on that buffer. In such
a case C1 would modify the free buffer list while C2 was potentially
accessing it, and this would eventually lead to lost memory buffers (or a
corrupt linked list). If all buffers become lost then ACL packets
(asynchronous events) can no longer be delivered from C2 to C1.
This commit fixes this issue by waiting for C2 to indicate that it has
finished using the free buffer list.
Work done in collaboration with Jim Mussared aka @jimmo.
Signed-off-by: Damien George <damien@micropython.org>
This change allows to build firmware for different rp2-based boards,
following how it is done in other ports like stm32 and esp32. So far only
the original Pico and Adafruit Feather RP2040 are added. Board names
should match (sans case) those in pico-sdk/src/boards/include/boards/.
Usage: Pico firmware can be build either using make as previously (it is
the default board) or by `make BOARD=PICO`. Feather is built by `make
BOARD=ADAFRUIT_FEATHER_RP2040`. Only the board name and flash drive size
is set, pin definition is taken from the appropriate pico-sdk board
definition. Firmware is saved in the directory build-BOARD_NAME.
Instantiation and init now support the rxbuf and txbuf keywords for setting
the buffer size. The default size is 256 bytes. The minimum and maximum
sizes are 32 and 32766 respectively.
uart.write() still includes checks for timeout, even if it is very unlikely
to happen due to a) lack of flow control support and b) the minimal timeout
values being longer than the time it needs to send a byte.
StateMachine.restart: Restarts the state machine
StateMachine.rx_fifo: Return the number of RX FIFO items, 0 if empty
StateMachine.tx_fifo: Return the number of TX FIFO items, 0 if empty
restart() seems to be the most useful one, as it resets the state machine
to the initial state without the need to re-initialise/re-create. It also
makes PIO code easier, because then stalling as an error state can be
unlocked.
rx_fifo() is also useful, for MP code to check for data and timeout if no
data arrived. Complex logic is easier handled in Python code than in PIO
code.
tx_fifo() can be useful to check states where data is not processed, and is
mostly for symmetry.
The implementation samples rosc.randombits at a frequency lower than the
oscillator frequency. This gives better random values. In addition, for
an 8-bit value 8 samples are taken and fed through a 8-bit CRC,
distributing the sampling over the byte. The resulting sampling rate is
about 120k/sec.
The RNG does not include testing of error conditions, like the ROSC being
in sync with the sampling or completely failing. Making the interim value
static causes it to perform a little bit better in short sync or drop-out
situations.
The output of uos.urandom() performs well with the NIST800-22 test suite.
In my trial it passed all tests of the sts 2.1.2 test suite. I also ran a
test of the random data with the Common Criteria test suite AIS 31, and it
passed all tests too.
STM32L476RG MCU of NUCLEO_L476RG board has 6 UART/USART units in total
(USART1, USART2, USART3, UART4, UART5 and LPUART1), but only UART2,
connected to REPL, was defined and available in Python code.
Defined are all 5 remaining UART/USART units including LPUART1.
Signed-off-by: Alexander Ziubin aziubin@googlemail.com
This commit simplifies the customisation of the main MicroPython execution
loop (4 macros are reduced to 2), and allows a board to have full control
over the execution (or not) of boot.py and main.py.
For boards that use the default start-up code, there is no functional
change in this commit.
Signed-off-by: Damien George <damien@micropython.org>
Per CPython everything which comes after the command, module or file
argument is not an option for the interpreter itself. Hence the processing
of options should stop when encountering those, and the remainder be passed
as sys.argv. Note the latter was already the case for a module or file but
not for a command.
This fixes issues like 'micropython myfile.py -h' showing the help and
exiting instead of passing '-h' as sys.argv[1], likewise for
'-X <something>' being treated as a special option no matter where it
occurs on the command line.
Some forum users noticed that `sm.exec()` took longer the more was present
on the flash filesystem connected to the RP2040. They traced this back to
the `array` import inside `asm_pio()`, which is causing MicroPython to scan
the filesystem.
uarray is a built-in module, so importing it shouldn't require scanning the
filesystem.
We avoid moving the import to the top-level in order to keep the namespace
clean; we don't want to accidentally expose `rp2.array`.
Support for C++ was added in 97960dc7de but
that commit didn't include the C++ exception handling table in the binary
firmware image. This commit fixes that.
Signed-off-by: Damien George <damien@micropython.org>
This is a workaround for errata RP2040-E5, and is needed to make USB more
reliable on certain USB ports.
Signed-off-by: Damien George <damien@micropython.org>
It's a bit of a pitfall with user C modules that including them in the
build does not automatically enable them. This commit changes the docs and
examples for user C modules to encourage writers of user C modules to
enable them unconditionally. This makes things simpler and covers most use
cases.
See discussion in issue #6960, and also #7086.
Signed-off-by: Damien George <damien@micropython.org>
It was noticed that the esp32 port didn't build ulab correctly. The
problem was a multiple defintion of the 'mp_hal_stdout_tx_str' and
'mp_hal_stdout_tx_strn_cooked' functions.
They were defined in stdout_helpers.c but also in the
ports/esp32/mphalport.c.
Fixed by removing stdout_helpers.c from the build.
Signed-off-by: Michael O'Cleirigh <michael.ocleirigh@rivulet.ca>
Support for User C and C++ modules was lost due to upgrading the esp32 to
the latest CMake based IDF from the GNUMakefile build process.
Restore the support for the esp32 port by integrating with the approach
recently added for the rp2 port.
Signed-off-by: Michael O'Cleirigh <michael.ocleirigh@rivulet.ca>
This USB feature is currently not supported. With this flag enabled (and
the feature not implemented) the USB serial will stop working if there is a
delay of more than about 2 seconds between messages, which can occur with
USB autosuspend enabled.
Fixes issue #6866.
