Commit Graph

842 Commits

Author SHA1 Message Date
Damien George dadee5fa24 esp32/modsocket: Fix crashes when connect/bind can't resolve given addr.
Fixes issue #4441.
2019-01-30 12:40:50 +11:00
Damien George 38022ddb2c stm32/main: Make board-defined UART REPL use a static object and buffer.
This way the UART REPL does not need the MicroPython heap and exists
outside the MicroPython runtime, allowing characters to still be received
during a soft reset.
2019-01-28 22:56:55 +11:00
Damien George f431795caf esp32/boards: Use auto xtal freq config instead of default 40MHz.
Auto-detection of the crystal frequency is convenient and allows for a
single binary for many different boards.  But it can be unreliable in
certain situations so in production, for a given board, it's recommended to
configure the correct fixed frequency.
2019-01-28 20:42:12 +11:00
Damien George 5d88272342 esp32/Makefile: Make sure that directory exists for sdkconfig.h. 2019-01-28 20:41:13 +11:00
Damien George 9ac9aa989c esp32/machine_timer: Deinit all active timers on soft reset.
Otherwise they will keep triggering the callback and access invalid data on
the heap.
2019-01-28 16:16:03 +11:00
Damien George 3d49b157b8 esp32: Update to latest ESP IDF using sdkconfig and new ldgen procedure.
Configuration for the build is now specified using sdkconfig rather than
sdkconfig.h, which allows for much easier configuration with defaults from
the ESP IDF automatically applied.  sdkconfig.h is generated using the new
ESP IDF kconfig_new tool written in Python.  Custom configuration for a
particular ESP32 board can be specified via the make variable SDKCONFIG.

The esp32.common.ld file is also now generated using the standard ESP IDF
ldgen.py tool.
2019-01-28 12:44:03 +11:00
Damien George f59904f799 esp32/Makefile: Put all IDF compenents in .a libs to use IDF ld script.
When the ESP IDF builds a project it puts all separate components into
separate .a library archives.  And then the esp32.common.ld linker script
references these .a libraries by explicit name to put certain object files
in iRAM.

This patch does a similar thing for the custom build system used here,
putting all IDF .o's into their respective .a.  So a custom linker script
is no longer needed.
2019-01-28 12:41:37 +11:00
Damien George e7ab475276 esp32: Don't put py/scheduler.o in iRAM, it's no longer needed.
ISR's no longer need to be in iRAM, and the ESP IDF provides an option to
specify that they are in iRAM if an application needs lower latency when
handling them.  But we don't use this feature for user interrupts: both
timer and gpio ISR routines are registered without the ESP_INTR_FLAG_IRAM
option, and so the scheduling code no longer needs to be in iRAM.
2019-01-27 16:15:47 +11:00
Damien George 4caf5b2358 stm32/usbdev: Add USB config option for max power drawn by the board.
The new compile-time option is MICROPY_HW_USB_MAX_POWER_MA.  Set this in
the board configuration file to the maximum current in mA that the board
will draw over USB.  The default is 500mA.
2019-01-27 14:02:10 +11:00
Damien George 7d8db42d17 stm32/usbdev: Add USB config option for board being self powered.
The new compile-time option is MICROPY_HW_USB_SELF_POWERED.  Set this
option to 1 in the board configuration file to indicate that the USB device
is self powered.  This option is disabled by default (previous behaviour).
2019-01-27 13:52:43 +11:00
Damien George c2886868b9 stm32/rtc: Check RTCEN=1 when testing if RTC is already running on boot.
It can be that LSEON and LSERDY are set yet the RTC is not enabled (this
can happen for example when coming out of the ST DFU mode on an F405 with
the RTC not previously initialised).  In such a case the RTC is never
started because the code thinks it's already running.  This patch fixes
this case by always checking if RTCEN is set when booting up (and also
testing for a valid RTCSEL value in the case of using an LSE).
2019-01-27 13:21:31 +11:00
stijn 42863830be py: Add optional support for 2-argument version of built-in next().
Configurable via MICROPY_PY_BUILTINS_NEXT2, disabled by default.
2019-01-27 13:01:28 +11:00
Reagan Sanders 51577629b2 cc3200/mods/modussl: Fix ca_certs arg validation in mod_ssl_wrap_socket.
Commit a0d97fe408 changed the argument index
of ca_certs but missed updating one of the references to the new index.
2019-01-27 12:51:34 +11:00
Mikhail Zakharov 18723e9889 unix/mpthreadport: Remove busy wait loop in thread garbage collection.
One can't use pthread calls in a signal handler because they are not
async-signal-safe (see man signal-safety).  Instead, sem_post can be used
to post from within a signal handler and this should be more efficient than
using a busy wait loop, waiting on a volatile variable.
2019-01-27 12:40:10 +11:00
Mikhail Zakharov 1e7b422226 unix/mpthreadport: Cleanup used memory on thread exit. 2019-01-27 12:39:45 +11:00
Mikhail Zakharov f8c1be85d1 unix/mpthreadport: Add thread deinit code to stop threads on exit.
Free unused memory for threads and cancel any outstanding threads on
interpreter exit to avoid possible segmentaiton fault.
2019-01-27 12:38:23 +11:00
Damien George 285d265eee stm32: Implement machine.lightsleep(). 2019-01-27 11:13:32 +11:00
Damien George 6d480f50ac pic16bit: Update to compile with latest xc16 v1.35 compiler.
This port has been verified to work with these latest changes.
2019-01-25 16:06:13 +11:00
Damien George da72bb6833 esp32/machine_hw_spi: Make HW SPI objects statically allocated.
This aligns more closely with the hardware, that there are two, fixed HW
SPI peripherals.  And it allows to recreate the HW SPI objects without
error, as well as create them again after a soft reset.

Fixes issue #4103.
2019-01-23 23:47:36 +11:00
Damien George d82f344f61 esp32/machine_hw_spi: Use separate DMA channels for HSPI and VSPI.
Otherwise only one of HSPI or VSPI can be used at a time.  Fixes
issue #4068.
2019-01-23 23:40:06 +11:00
Matt Trentini cd52d2c691 esp32/modules/neopixel.py: Change NeoPixel to different default timings.
In order to suit the more common 800KHz by default (instead of 400KHz), and
also have the same behaviour as the esp8266 port.

Resolves #4396.

Note! This is a breaking change. Anyone that has previously used the
NeoPixel class on an ESP32 board may be affected.
2019-01-23 14:22:38 +11:00
Damien George 18d3a5df26 esp8266/esp_mphal: Provide mp_hal_pin_od_high_dht so DHT works reliably.
The original behaviour of open-drain-high was to use the open-drain mode of
the GPIO pin, and this seems to make driving a DHT more reliable.  See
issue #4233.
2019-01-22 00:26:04 +11:00
Damien George eb446ec227 esp32/Makefile: Use system provided math library rather than uPy one.
The ESP IDF system already provides a math library, and that one is likely
to be better tuned to the Xtensa architecture.  The IDF components are also
tested against its own math library, so best not to override it.  Using the
system provided library also allows to easily switch to double-precision
floating point by changing MICROPY_FLOAT_IMPL to MICROPY_FLOAT_IMPL_DOUBLE.
2019-01-17 16:43:20 +11:00
Damien George 90f86a0197 esp32/machine_pin: Add Pin.off() and Pin.on() methods. 2019-01-16 17:33:56 +11:00
Damien George 36808d4e6a esp8266/main: Activate UART(0) on dupterm for REPL before boot.py runs.
So that the user can explicitly deactivate UART(0) if needed.  See
issue #4314.

This introduces some risk to "brick" the device, if the user disables the
REPL without providing an alternative REPL (eg WebREPL), or any way to
reenable it.  In such a case the device needs to be erased and
reprogrammed.  This seems unavoidable, given the desire to have the option
to use the UART for something other than the REPL.
2019-01-16 17:24:23 +11:00
Damien George 3431ea7205 stm32/main: Make thread and FS state static and exclude when not needed.
Without the static qualifier these objects will be kept by the linker even
if they are unused.  So this patch saves some RAM when these features are
unused by a board.
2019-01-11 01:52:17 +11:00
Damien George 5b66c7b712 stm32/wdt: Make singleton WDT object const so it goes in ROM. 2019-01-11 01:51:57 +11:00
Damien George f350b640a0 esp32/modsocket: For socket read only release GIL if socket would block.
If there are many short reads to a socket in a row (eg by readline) then
releasing and acquiring the GIL each time will give very poor throughput.
So first poll the socket to see if it has data, and if it does then don't
release the GIL.
2019-01-10 15:46:44 +11:00
Damien George efe0569c26 esp32/mphalport: When tx'ing to REPL only release GIL if many chars sent
Otherwise, if multiple threads are active, printing data to the REPL may be
very slow because in some cases only one character is output per call to
mp_hal_stdout_tx_strn.
2019-01-10 15:43:47 +11:00
Damien George b33f108cde stm32/sdcard: Properly reset SD periph when SDMMC2 is used on H7 MCUs. 2018-12-30 01:28:34 +11:00
roland 4d8504425a stm32/modmachine: Fix reset_cause to correctly give DEEPSLEEP on L4 MCU.
Before this fix it returned SOFT_RESET after waking from a deepsleep
(standby).
2018-12-30 01:11:25 +11:00
Damien George f334816df0 stm32/uart: Make sure user IRQs are handled even with a keyboard intr. 2018-12-30 01:03:22 +11:00
Damien George 7bdbea9a0c stm32/uart: Clear overrun error flag after reading RX data register.
On MCUs other than F4 the ORE (overrun error) flag needs to be cleared
independently of clearing RXNE, even though both are wired to trigger the
same RXNE IRQ.  In the case that an overrun occurred it's necessary to
explicitly clear the ORE flag or else the RXNE interrupt will keep firing.
2018-12-30 00:59:16 +11:00
Damien George 0d860fdcd0 stm32/uart: Always enable global UART IRQ handler on init.
Otherwise IRQs may not be enabled for the user UART.irq() handler.  In
particular this fixes the user IRQ_RXIDLE interrupt so that it triggers
even when there is no RX buffer.
2018-12-29 22:44:41 +11:00
Damien George a5f7a3022d stm32/uart: Fix uart_rx_any in case of no buffer to return 0 or 1. 2018-12-29 22:43:35 +11:00
Tobias Badertscher 372e7a4dc6 stm32: Implement UART.irq() method with initial support for RX idle IRQ. 2018-12-29 17:21:37 +11:00
Andrew Leech ce0c581179 stm32/main: Add board config option to enable/disable mounting SD card.
The new option MICROPY_HW_SDCARD_MOUNT_AT_BOOT can now be defined to 0 in
mpconfigboard.h to allow SD hardware to be enabled but not auto-mounted at
boot.  This feature is enabled by default to retain previous behaviour.

Previously, if an SD card is enabled in hardware it is also used to boot
from.  While this can be disabled with a SKIPSD file on internal flash,
this wont be available at first boot or if the internal flash gets
corrupted.
2018-12-22 01:30:47 +11:00
Damien George 0c46419323 windows: Remove remaining traces of old GNU readline support.
GNU readline support for the unix port was removed in
acaa30b604 and in
5e83a75c78, so it's also no longer supported
in the windows port.
2018-12-15 13:54:55 +11:00
Damien George 5146e79490 stm32/boards/NUCLEO_L432KC: Specify L4 OpenOCD config file for this MCU. 2018-12-13 13:45:16 +11:00
Damien George 59f409a787 stm32/boards: Allow OpenOCD stm_flash procedure to accept single FW img.
To support deplop-openocd on target boards that use TEXT0_ADDR only and
have their firmware in a single binary image.
2018-12-13 13:43:10 +11:00
Paul Sokolovsky fbb8335084 py/objdict: Make .fromkeys() method configurable.
On by default, turned off for minimal/bare-arm. Saves 144 bytes on x86.
2018-12-13 01:20:55 +11:00
Damien George 1db55381b6 stm32/adc: Support 16-bit ADC configuration on H7 MCUs. 2018-12-12 12:51:46 +11:00
Damien George 6cab8daee0 stm32/adc: Increase ADC sampling time for internal sources on H7 MCUs. 2018-12-12 12:51:26 +11:00
Damien George 0555ada277 stm32/adc: Fix calibrated volt/temp readings on H7 by using 16bit scale. 2018-12-12 12:50:37 +11:00
Damien George 1b4031ed64 stm32/extint: Use correct EXTI channels on H7 MCUs for RTC events. 2018-12-12 12:49:23 +11:00
Glenn Ruben Bakke 9e5768a6db nrf/bluetooth: Update BLE stack download script.
Due to new webpages at nordicsemi.com, the download links
for Bluetooth LE stacks were broken.

This patch updates the links to new locations for the current
targets.
2018-12-10 20:42:06 +01:00
Damien George 025d419a77 teensy: Add own uart.h to not rely on stm32's version of the file. 2018-12-10 23:55:11 +11:00
Damien George dc23978dde stm32/uart: Add ability to have a static built-in UART object.
A static UART is useful for internal peripherals that require a UART and
need to persist outside the soft-reset loop.
2018-12-10 16:21:50 +11:00
Damien George 61ef031687 stm32/uart: Move config of char_width/char_mask to uart.c. 2018-12-10 16:21:50 +11:00
Damien George 6ea45277bf stm32/uart: For UART init, pass in params directly, not via HAL struct.
To provide a cleaner and more abstract C-level interface to the UART.
2018-12-10 16:21:50 +11:00
Damien George e0c2432503 stm32/uart: Simplify deinit of UART, no need to call HAL.
The HAL just clears UE and then clears all the UART control registers.
2018-12-10 16:21:50 +11:00
Damien George bc3f0dddac stm32/uart: Remove HAL's UART_HandleTypeDef from UART object struct.
This UART_HandleTypeDef is quite large (around 70 bytes in RAM needed for
each UART object) and is not needed: instead the state of the peripheral
held in its registers provides all the required information.
2018-12-10 16:21:50 +11:00
Damien George 7d7f59d78b stm32/uart: Factor out code to set RX buffer to function uart_set_rxbuf. 2018-12-10 16:21:50 +11:00
Damien George 9690757cca stm32/uart: Rework uart_get_baudrate so it doesn't need a UART handle. 2018-12-10 16:21:50 +11:00
Damien George 524e13b006 stm32/uart: Factor out code from machine_uart.c that computes baudrate. 2018-12-10 16:21:50 +11:00
Damien George a2271532be stm32: Split out UART Python bindings from uart.c to machine_uart.c. 2018-12-10 16:21:50 +11:00
Damien George da7355e213 esp32/modmachine: Enable machine.sleep() now that the IDF supports it. 2018-12-06 17:23:27 +11:00
Damien George 9c6c32cc51 esp32/machine_pwm: On deinit stop routing PWM signal to the pin.
Fixes issue #4273.
2018-12-06 17:05:16 +11:00
Damien George 287b02d98a esp32/machine_pwm: Support higher PWM freq by auto-scaling timer res. 2018-12-06 16:43:39 +11:00
Damien George 87623082e3 esp32/machine_uart: Implement UART.sendbreak() method.
The uart_write_bytes_with_break() function requires non-zero data to be
sent before the break, so a standalone break must be synthesised.
2018-12-06 15:40:22 +11:00
boochow 69b7b8fa12 stm32/boards: Add NUCLEO_L432KC board configuration files. 2018-12-06 13:33:29 +11:00
boochow 9d3372bded stm32: Add peripheral support for STM32L432.
The L432 does not have: GPIOD, TIM3, SPI2, ADC dual mode operation, 2-banks
flash.
2018-12-06 13:32:43 +11:00
boochow 1a8baad7ca stm32/boards: Add STM32L432KC chip configuration files.
The pin alternate function information is derived from ST's datasheet
https://www.st.com/resource/en/datasheet/stm32l432kc.pdf
In the datasheet, the line 2 of AF4 includes I2C2 but actually the chip
does not have I2C2 so it is removed.
2018-12-06 13:32:43 +11:00
Damien George 52bec93755 esp8266/machine_uart: Add rxbuf keyword arg to UART constructor/init.
As per the machine.UART documentation, this is used to set the length of
the UART RX buffer.
2018-12-05 23:31:24 +11:00
Damien George 9ddc182ec7 esp32/machine_uart: Add txbuf/rxbuf keyword args to UART construct/init.
As per the machine.UART documentation, these are used to set the length of
the TX and RX buffers.
2018-12-05 16:48:34 +11:00
Damien George 8007d0bd16 stm32/uart: Add rxbuf keyword arg to UART constructor and init method.
As per the machine.UART documentation, this is used to set the length of
the RX buffer.  The legacy read_buf_len argument is retained for backwards
compatibility, with rxbuf overriding it if provided.
2018-12-05 13:24:11 +11:00
Damien George c6365ffb92 stm32/powerctrl: Add support for standby mode on L4 MCUs.
This maps to machine.deepsleep() which is now supported.
2018-12-05 00:40:05 +11:00
Damien George a1c81761b1 stm32/mboot: Add documentation for using mboot on PYBv1.x. 2018-12-04 23:48:47 +11:00
Damien George c040961e91 stm32/boards: Add configuration for putting mboot on PYBv1.x. 2018-12-04 23:48:18 +11:00
Damien George eed522d69f stm32/mboot: Add support for 4th board LED. 2018-12-04 23:14:30 +11:00
Damien George 13e92e1225 stm32/mboot: Provide led_state_all function to reduce code size. 2018-12-04 23:11:51 +11:00
Damien George 9262f54138 stm32/uart: Always show the flow setting when printing a UART object.
Also change the order of printing of flow so it is after stop (so bits,
parity, stop are one after the other), and reduce code size by using
mp_print_str instead of mp_printf where possible.

See issue #1981.
2018-12-04 19:16:16 +11:00
Damien George da1d849ad1 stm32,esp8266,cc3200: Use MICROPY_GC_STACK_ENTRY_TYPE to save some RAM. 2018-12-04 18:32:10 +11:00
Damien George 62b4bebf64 esp8266/modnetwork: Wait for iface to go down before forcing power mgmt.
If the STA interface is connected to an AP then it must be fully
disconnected and deactivated before forcing the power management on.
2018-12-04 10:20:45 +11:00
roland 10bddc5c28 stm32/boards/STM32F429DISC: Enable UART as secondary REPL.
The board(s) feature a VCOM through the ST-LINK, this feature is something
to keep around.
2018-12-01 17:30:48 +11:00
Damien George 321d75e087 esp8266/modnetwork: Automatically do radio sleep if no interface active.
Reduces current of device by about 55mA when radio is sleeping.
2018-12-01 17:20:05 +11:00
Damien George 9e2dd93145 esp8266/ets_alt_task: Process idle callback if no other events occurred. 2018-12-01 17:20:05 +11:00
Damien George 485514f57a esp32: Allocate task TCB and stack from system heap not uPy heap.
This is necessary for two reasons: 1) FreeRTOS still needs the TCB data
structure even after vPortCleanUpTCB has been called, so this latter hook
function cannot free the TCB, and there is no where else to safely delete
it (this behaviour has changed recently in the ESP IDF); 2) when using
external SPI RAM the uPy heap is in this external memory but the task stack
must be allocated from internal SRAM.

Fixes issue #3904.
2018-11-28 15:00:45 +11:00
Damien George 0233049b79 esp32/mpthreadport: Prevent deadlocks when deleting all threads.
vTaskDelete now immediately calls vPortCleanUpTCB, which requires the
thread_mutex mutex, so vTaskDelete must be called after this mutex is
released.
2018-11-28 14:30:11 +11:00
Damien George afd1ce0c15 stm32/powerctrl: Disable IRQs during stop mode to allow reconfig on wake 2018-11-28 12:44:54 +11:00
Damien George 66ca8e9b2c stm32/powerctrl: Move (deep)sleep funcs from modmachine.c to powerctrl.c 2018-11-28 12:22:20 +11:00
Damien George 3a723ad2fe stm32/usb: Fully deinitialise USB periph when it is deactivated. 2018-11-28 12:06:47 +11:00
Damien George 5f67b03e99 stm32/servo: Only initialise TIM5 if it is needed, to save power. 2018-11-28 12:06:24 +11:00
Paul Sokolovsky 80aca27a40 unix/modos: Rename unlink to remove to be consistent with other ports.
We standardized to provide uos.remove() as a more obvious and user-friendly
name.  That's what written in the docs.  The Unix port implementation
predates this convention, so update it now.
2018-11-26 23:27:04 +11:00
Michael Paul Coder fe452afab2 stm32/flashbdev: Add missing include for irq.h.
This is required for mboot to build.
2018-11-26 16:34:13 +11:00
Tobias Badertscher 9acc32b40f stm32/adc: Add ADC auto-calibration for L4 MCUs.
This increases the precision of the ADC.
2018-11-26 16:16:29 +11:00
Damien George 51482ba925 README: Remove references to "make axtls", it's no longer needed.
Since 0be2ea50e9 axtls is automatically built
as part of the usual "make" build process.
2018-11-15 14:48:17 +11:00
roland 30ed2b3cab stm32/system_stm32: Introduce configuration defines for PLL3 settings.
A board must be able to set the PLL3 values based on the HSE that it uses.
2018-11-01 13:25:47 +11:00
Damien George 746dbf78d3 py/py.mk: When building axtls use -Wno-all to prevent all warnings.
Building axtls gives a lot of warnings with -Wall enabled, and explicitly
disabling all of them cannot be done in a way compatible with gcc and
clang, and likely other compilers.  So just use -Wno-all to prevent all of
the extra warnings (in addition to the necessary -Wno-unused-parameter,
-Wno-uninitialized, -Wno-sign-compare and -Wno-old-style-definition).

Fixes issue #4182.
2018-10-27 23:53:08 +11:00
Paul m. p. P 454cca6016 py/objmodule: Implement PEP 562's __getattr__ for modules.
Configurable via MICROPY_MODULE_GETATTR, disabled by default.  Among other
things __getattr__ for modules can help to build lazy loading / code
unloading at runtime.
2018-10-23 11:22:50 +11:00
Paul Sokolovsky 5a91fce9f8 py/objstr: Make str.count() method configurable.
Configurable via MICROPY_PY_BUILTINS_STR_COUNT.  Default is enabled.
Disabled for bare-arm, minimal, unix-minimal and zephyr ports.  Disabling
it saves 408 bytes on x86.
2018-10-22 22:49:05 +11:00
Eric Poulsen 3c6f639aa5 esp32/network_ppp: Add PPPoS functionality.
This commit adds network.PPP(stream) which allows to create a TCP/IP
network interface over a stream object (eg a UART).
2018-10-19 23:32:02 +11:00
Eric Poulsen 5e5aef53fb esp32/modesp32: Add hall_sensor() function. 2018-10-19 17:28:02 +11:00
Paul Sokolovsky 6ddcfe68b8 unix/Makefile: Allow to override/omit pthread lib name.
For example, on Android, pthread functions are part of libc, so LIBPTHREAD
should be empty.
2018-10-19 17:22:37 +11:00
Damien George d2c5496894 stm32/boards/stm32h743.ld: Fix total flash size, should be 2048k.
Fixes issue #4240.
2018-10-17 15:29:56 +11:00
iabdalkader f0db1a5ab1 stm32/spi: Fix calculation of SPI clock source on H7 MCUs. 2018-10-17 15:26:26 +11:00
Paul Sokolovsky 6c5b2bded2 unix/modffi: Add support for "q"/"Q" specs (int64_t/uint64_t). 2018-10-17 15:17:05 +11:00
Paul Sokolovsky 0c18633ea9 unix/modusocket: Finish socket.settimeout() implementation.
1. Return correct error code for non-blocking vs timed out socket
(POSIX returns EAGAIN for both, we want ETIMEDOUT in case of timed
out socket). To achieve this, blocking/non-blocking flag is added
to the mp_obj_socket_t, to avoid issuing fcntl() syscall each time
EAGAIN occurs. (mp_obj_socket_t used to be 8 bytes, having some room
in a standard 16-byte alloc block.)

2. Handle socket.settimeout(0) properly - in Python, that means
non-blocking mode, but SO_RCVTIMEO/SO_SNDTIMEO of 0 is infinite
timeout.

3. Overall, make sure that socket.settimeout() call switches blocking
state as expected.
2018-10-17 14:19:06 +11:00
Danielle Madeley 80a25810f9 unix/modusocket: Initial implementation of socket.settimeout(). 2018-10-17 14:19:06 +11:00
Damien George 0f6f86ca49 stm32/usbd_cdc_interface: Refactor USB CDC tx code to not use SOF IRQ.
Prior to this commit the USB CDC used the USB start-of-frame (SOF) IRQ to
regularly check if buffered data needed to be sent out to the USB host.
This wasted resources (CPU, power) if no data needed to be sent.

This commit changes how the USB CDC transmits buffered data:
- When new data is first available to send the data is queued immediately
  on the USB IN endpoint, ready to be sent as soon as possible.
- Subsequent additions to the buffer (via usbd_cdc_try_tx()) will wait.
- When the low-level USB driver has finished sending out the data queued
  in the USB IN endpoint it calls usbd_cdc_tx_ready() which immediately
  queues any outstanding data, waiting for the next IN frame.

The benefits on this new approach are:
- SOF IRQ does not need to run continuously so device has a better chance
  to sleep for longer, and be more responsive to other IRQs.
- Because SOF IRQ is off, current consumption is reduced by a small amount,
  roughly 200uA when USB is connected (measured on PYBv1.0).
- CDC tx throughput (USB IN) on PYBv1.0 is about 2.3 faster (USB OUT is
  unchanged).
- When USB is connected, Python code that is executing is slightly faster
  because SOF IRQ no longer interrupts continuously.
- On F733 with USB HS, CDC tx throughput is about the same as prior to this
  commit.
- On F733 with USB HS, Python code is about 5% faster because of no SOF.

As part of this refactor, the serial port should no longer echo initial
characters when the serial port is first opened (this only used to happen
rarely on USB FS, but on USB HS is was more evident).
2018-10-15 15:37:01 +11:00