2021-06-18 15:12:44 +00:00
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.. _mimxrt_quickref:
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Quick reference for the i.MXRT family
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=====================================
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.. image:: img/teensy_4.1.jpg
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:alt: Teensy 4.1 board
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:width: 640px
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The Teensy 4.1 board.
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Below is a quick reference for i.MXRT-based boards. If it is your first time
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working with this board it may be useful to get an overview of the microcontroller:
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.. toctree::
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:maxdepth: 1
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general.rst
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tutorial/intro.rst
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2022-04-08 12:20:44 +00:00
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pinout.rst
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2021-06-18 15:12:44 +00:00
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Installing MicroPython
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----------------------
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See the corresponding section of tutorial: :ref:`mimxrt_intro`. It also includes
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a troubleshooting subsection.
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General board control
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---------------------
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The MicroPython REPL is on the USB port, configured in VCP mode.
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Tab-completion is useful to find out what methods an object has.
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Paste mode (ctrl-E) is useful to paste a large slab of Python code into
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the REPL.
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The :mod:`machine` module::
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import machine
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machine.freq() # get the current frequency of the CPU
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Delay and timing
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----------------
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Use the :mod:`time <time>` module::
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import time
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time.sleep(1) # sleep for 1 second
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time.sleep_ms(500) # sleep for 500 milliseconds
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time.sleep_us(10) # sleep for 10 microseconds
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start = time.ticks_ms() # get millisecond counter
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delta = time.ticks_diff(time.ticks_ms(), start) # compute time difference
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Timers
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------
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2022-10-15 09:40:22 +00:00
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The i.MXRT port supports virtual Timers. Example of usage::
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from machine import Timer
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2022-10-15 09:40:22 +00:00
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tim0 = Timer(-1)
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tim0.init(period=5000, mode=Timer.ONE_SHOT, callback=lambda t:print(0))
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tim1 = Timer(-1)
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tim1.init(period=2000, mode=Timer.PERIODIC, callback=lambda t:print(1))
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The period is in milliseconds.
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.. _mimxrt_Pins_and_GPIO:
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Pins and GPIO
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-------------
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Use the :ref:`machine.Pin <machine.Pin>` class::
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from machine import Pin
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p0 = Pin('D0', Pin.OUT) # create output pin on GPIO0
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p0.on() # set pin to "on" (high) level
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p0.off() # set pin to "off" (low) level
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p0.value(1) # set pin to on/high
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p2 = Pin('D2', Pin.IN) # create input pin on GPIO2
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print(p2.value()) # get value, 0 or 1
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p4 = Pin('D4', Pin.IN, Pin.PULL_UP) # enable internal pull-up resistor
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p5 = Pin('D5', Pin.OUT, value=1) # set pin high on creation
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p6 = Pin(pin.cpu.GPIO_B1_15, Pin.OUT) # Use the cpu pin name.
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Available Pins follow the ranges and labelling of the respective board, like:
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- 0-33 for Teensy 4.0,
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- 0-21 for the MIMXRT10xx-EVK board, or 'D0-Dxx', or 'A0-Ann',
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- 0-14 for the Olimex RT1010Py board, or 'D0'-'Dxx' and 'A0'-'Ann'
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- 'J3_xx', 'J4_xx', 'J5_xx' for the Seeed ARCH MIX board,
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or the pin names of the Pin.board or Pin.cpu classes.
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Notes:
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* The MIMXRT1xxx-EVK boards may have other on-board devices connected to these
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pins, limiting it's use for input or output.
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* At the MIMXRT1010_EVK, pins D4, D5 and D9 of the Arduino connector are by
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default not connected to the MCU. For details refer to the schematics.
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* At the MIMXRT1170_EVK board, the inner rows of the Arduino connectors are assigned as follows:
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- D16 - D23: J9, odd pin numbers; D17 is by default not connected.
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- D24 - D27: J26, odd pin numbers; J63-J66 have to be closed to enable these pins.
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- D29 - D36: J25, odd pin numbers; D29 and D30 are by default not connected.
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There's a higher-level abstraction :ref:`machine.Signal <machine.Signal>`
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which can be used to invert a pin. Useful for illuminating active-low LEDs
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using ``on()`` or ``value(1)``.
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UART (serial bus)
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-----------------
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See :ref:`machine.UART <machine.UART>`. ::
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from machine import UART
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uart1 = UART(1, baudrate=115200)
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uart1.write('hello') # write 5 bytes
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uart1.read(5) # read up to 5 bytes
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The i.MXRT has up to eight hardware UARTs, but not every board exposes all
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TX and RX pins for users. For the assignment of Pins to UART signals,
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refer to the :ref:`UART pinout <mimxrt_uart_pinout>`.
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PWM (pulse width modulation)
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----------------------------
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The i.MXRT has up to four dedicated PWM modules with four FLEXPWM submodules each
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and up to four QTMR modules with four channels, which can be used to generate
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a PWM signal or signal pair.
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The PWM functions are provided by the :ref:`machine.PWM <machine.PWM>` class.
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It supports all basic methods listed for that class and a few additional methods for
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handling signal groups. ::
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# Samples for Teensy
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#
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from machine import Pin, PWM
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pwm2 = PWM(Pin(2)) # create PWM object from a pin
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pwm2.freq() # get current frequency
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pwm2.freq(1000) # set frequency
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pwm2.duty_u16() # get current duty cycle, range 0-65535
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pwm2.duty_u16(200) # set duty cycle, range 0-65535
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pwm2.deinit() # turn off PWM on the pin
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# create a complementary signal pair on Pin 2 and 3
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pwm2 = PWM((2, 3), freq=2000, duty_ns=20000)
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# Create a group of four synchronized signals.
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# Start with Pin(4) at submodule 0, which creates the sync pulse.
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pwm4 = PWM(Pin(4), freq=1000, align=PWM.HEAD)
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# Pins 5, 6, and 9 are pins at the same module
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pwm5 = PWM(Pin(5), freq=1000, duty_u16=10000, align=PWM.HEAD, sync=True)
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pwm6 = PWM(Pin(6), freq=1000, duty_u16=20000, align=PWM.HEAD, sync=True)
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pwm9 = PWM(Pin(9), freq=1000, duty_u16=30000, align=PWM.HEAD, sync=True)
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pwm3 # show the PWM objects properties
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PWM Constructor
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```````````````
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.. class:: PWM(dest, freq, duty_u16, duty_ns, *, center, align, invert, sync, xor, deadtime)
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:noindex:
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Construct and return a new PWM object using the following parameters:
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- *dest* is the entity on which the PWM is output, which is usually a
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:ref:`machine.Pin <machine.Pin>` object, but a port may allow other values,
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like integers or strings, which designate a Pin in the machine.PIN class.
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*dest* is either a single object or a two element object tuple.
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If the object tuple is specified, the two pins act in complementary
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mode. These two pins must be the A/B channels of the same submodule.
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PWM objects are either provided by a FLEXPWM module or a QTMR module.
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The i.MXRT devices have either two or four FLEXPWM and QTMR modules.
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Each FLEXPWM module has four submodules with three channels, each,
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called A, B and X. Each QTMR module has four channels.
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Each FLEXPWM submodule or QTMR channel may be set to different parameters.
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Not every channel is routed to a board pin. Details are listed below.
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Setting *freq* affects the three channels of the same FLEXPWM submodule.
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Only one of *duty_u16* and *duty_ns* should be specified at a time.
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Keyword arguments:
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- *freq* should be an integer which sets the frequency in Hz for the
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PWM cycle. The valid frequency range is 15 Hz resp. 18Hz resp. 24Hz up to > 1 MHz.
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- *duty_u16* sets the duty cycle as a ratio ``duty_u16 / 65536``.
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The duty cycle of a X channel can only be changed, if the A and B channel
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of the respective submodule is not used. Otherwise the duty_16 value of the
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X channel is 32768 (50%).
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- *duty_ns* sets the pulse width in nanoseconds. The limitation for X channels
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apply as well.
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- *center*\=value. An integer sets the center of the pulse within the pulse period.
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The range is 0-65535. The resulting pulse will last from center - duty_u16/2 to
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center + duty_u16/2.
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- *align*\=value. Shortcuts for the pulse center setting, causing the pulse either at
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the center of the frame (value=0), the leading edge at the begin (value=1) or the
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trailing edge at the end of a pulse period (value=2).
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- *invert*\=True|False channel_mask. Setting a bit in the mask inverts the respective channel.
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Bit 0 inverts the first specified channel, bit 2 the second. The default is 0.
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- *sync*\=True|False. If a channel of a module's submodule 0 is already active, other
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submodules of the same module can be forced to be synchronous to submodule 0. Their
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pulse period start then at at same clock cycle. The default is False.
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- *xor*\=0|1|2. If set to 1 or 2, the channel will output the XOR'd signal from channels
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A or B. If set to 1 on channel A or B, both A and B will show the same signal. If set
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to 2, A and B will show alternating signals. For details and an illustration, please
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refer to the MCU's reference manual, chapter "Double Switching PWMs".
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- *deadtime*\=time_ns. This setting affects complementary channels and defines a deadtime
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between an edge of a first channel and the edge of the next channel, in which both
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channels are set to low. That allows connected H-bridges to switch off one side
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of a push-pull driver before switching on the other side.
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PWM Methods
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```````````
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The methods are identical to the generic :ref:`machine.PWM <machine.PWM>` class,
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with additional keyword arguments to the init() method, matchings those of the constructor.
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Each FLEX submodule or QTMR module may run at different frequencies. The PWM signal
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is created by dividing the pwm_clk signal by an integral factor, according to the formula::
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f = pwm_clk / (2**n * m)
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with n being in the range of 0..7, and m in the range of 2..65536. pmw_clk is 125Mhz
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for MIMXRT1010/1015/1020, 150 MHz for MIMXRT1050/1060/1064 and 160MHz for MIMXRT1170.
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The lowest frequency is pwm_clk/2**23 (15, 18, 20Hz). The highest frequency with
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U16 resolution is pwm_clk/2**16 (1907, 2288, 2441 Hz), the highest frequency
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with 1 percent resolution is pwm_clk/100 (1.25, 1.5, 1.6 MHz). The highest achievable
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frequency is pwm_clk/3 for the A/B channels, and pwm_clk/2 for the X channels and QTMR
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signal.
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PWM Pin Assignment
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``````````````````
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Pins are specified in the same way as for the Pin class. For the assignment of Pins
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to PWM signals, refer to the :ref:`PWM pinout <mimxrt_pwm_pinout>`.
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ADC (analog to digital conversion)
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----------------------------------
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On the i.MXRT ADC functionality is available on Pins labeled 'Ann'.
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Use the :ref:`machine.ADC <machine.ADC>` class::
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from machine import ADC
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adc = ADC(Pin(32)) # create ADC object on ADC pin
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adc.read_u16() # read value, 0-65536 across voltage range 0.0v - 3.3v
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The resolution of the ADC is 12 bit with 10 to 11 bit accuracy, irrespective of the
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value returned by read_u16(). If you need a higher resolution or better accuracy, use
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an external ADC.
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Software SPI bus
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----------------
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Software SPI (using bit-banging) works on all pins, and is accessed via the
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:ref:`machine.SoftSPI <machine.SoftSPI>` class. ::
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from machine import Pin, SoftSPI
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# construct a SoftSPI bus on the given pins
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# polarity is the idle state of SCK
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# phase=0 means sample on the first edge of SCK, phase=1 means the second
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spi = SoftSPI(baudrate=100000, polarity=1, phase=0, sck=Pin(0), mosi=Pin(2), miso=Pin(4))
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spi.init(baudrate=200000) # set the baudrate
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spi.read(10) # read 10 bytes on MISO
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spi.read(10, 0xff) # read 10 bytes while outputting 0xff on MOSI
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buf = bytearray(50) # create a buffer
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spi.readinto(buf) # read into the given buffer (reads 50 bytes in this case)
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spi.readinto(buf, 0xff) # read into the given buffer and output 0xff on MOSI
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spi.write(b'12345') # write 5 bytes on MOSI
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buf = bytearray(4) # create a buffer
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spi.write_readinto(b'1234', buf) # write to MOSI and read from MISO into the buffer
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spi.write_readinto(buf, buf) # write buf to MOSI and read MISO back into buf
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The highest supported baud rate is 500000.
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Hardware SPI bus
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----------------
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There are up to four hardware SPI channels that allow faster transmission
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rates (up to 30Mhz). Hardware SPI is accessed via the
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:ref:`machine.SPI <machine.SPI>` class and has the same methods as software SPI above::
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2022-07-31 09:09:57 +00:00
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from machine import SPI, Pin
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spi = SPI(0, 10000000)
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cs_pin = Pin(6, Pin.OUT, value=1)
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cs_pin(0)
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spi.write('Hello World')
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cs_pin(1)
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For the assignment of Pins to SPI signals, refer to
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:ref:`Hardware SPI pinout <mimxrt_spi_pinout>`.
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The keyword option cs=n can be used to enable the cs pin 0 or 1 for an automatic cs signal. The
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default is cs=-1. Using cs=-1 the automatic cs signal is not created.
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In that case, cs has to be set by the script. Clearing that assignment requires a power cycle.
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Notes:
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1. Even if the highest reliable baud rate at the moment is about 30 Mhz,
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setting a baud rate will not always result in exactly that
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frequency, especially at high baud rates.
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2. Sending at higher baud rate is possible. In the tests receiving
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worked up to 60 MHz, sending up to 90 MHz.
|
2021-06-18 15:12:44 +00:00
|
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|
|
Software I2C bus
|
|
|
|
----------------
|
|
|
|
|
|
|
|
Software I2C (using bit-banging) works on all output-capable pins, and is
|
|
|
|
accessed via the :ref:`machine.SoftI2C <machine.SoftI2C>` class::
|
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|
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|
|
|
from machine import Pin, SoftI2C
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|
|
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|
i2c = SoftI2C(scl=Pin(5), sda=Pin(4), freq=100000)
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|
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|
i2c.scan() # scan for devices
|
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|
|
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|
i2c.readfrom(0x3a, 4) # read 4 bytes from device with address 0x3a
|
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|
|
i2c.writeto(0x3a, '12') # write '12' to device with address 0x3a
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|
|
buf = bytearray(10) # create a buffer with 10 bytes
|
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|
|
i2c.writeto(0x3a, buf) # write the given buffer to the slave
|
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|
|
|
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|
|
The highest supported freq is 400000.
|
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|
|
|
|
Hardware I2C bus
|
|
|
|
----------------
|
|
|
|
|
|
|
|
There are up to four hardware I2C channels that allow faster transmission rates
|
|
|
|
and support the full I2C protocol. The I2C signals have fixed assignments to GPIO pins.
|
2022-04-08 12:20:44 +00:00
|
|
|
For the assignment of Pins to I2C signals, refer to :ref:`Hardware I2C pinout <mimxrt_i2c_pinout>`.
|
2021-06-18 15:12:44 +00:00
|
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|
|
Hardware I2C is accessed via the :ref:`machine.I2C <machine.I2C>` class and
|
|
|
|
has the same methods as software SPI above::
|
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|
|
|
|
|
|
from machine import I2C
|
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|
|
|
|
|
|
i2c = I2C(0, 400_000)
|
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|
|
i2c.writeto(0x76, b"Hello World")
|
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|
|
|
|
I2S bus
|
|
|
|
-------
|
|
|
|
|
|
|
|
See :ref:`machine.I2S <machine.I2S>`. Example using a Teensy 4.1 board with a simple
|
|
|
|
external Codec like UDA1334.::
|
|
|
|
|
|
|
|
from machine import I2S, Pin
|
|
|
|
i2s = I2S(2, sck=Pin(26), ws=Pin(27), sd=Pin(7),
|
|
|
|
mode=I2S.TX, bts=16,format=I2S.STEREO,
|
|
|
|
rate=44100,ibuf=40000)
|
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|
|
i2s.write(buf) # write buffer of audio samples to I2S device
|
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|
|
|
|
|
|
|
|
|
|
Example for using I2S with a MIMXRT10xx_DEV board::
|
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|
|
|
|
|
|
from machine import I2S, I2C, Pin
|
|
|
|
import wm8960
|
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|
|
|
|
|
|
i2c=I2C(0)
|
|
|
|
|
|
|
|
wm=wm8960.WM8960(i2c, sample_rate=SAMPLE_RATE_IN_HZ,
|
|
|
|
adc_sync=wm8960.sync_dac,
|
|
|
|
swap=wm8960.swap_input)
|
|
|
|
|
|
|
|
i2s = I2S(1, sck=Pin("SCK_TX"), ws=Pin("WS_TX"), sd=Pin("SD_RX"),
|
|
|
|
mck=Pin("MCK),mode=I2S.RX, bts=16,format=I2S.MONO,
|
|
|
|
rate=32000,ibuf=10000)
|
|
|
|
i2s.readinto(buf) # fill buffer with audio samples from I2S device
|
|
|
|
|
|
|
|
In this example, the input channels are swapped in the WM8960 driver, since the
|
|
|
|
on-board microphone is connected to the right channel, but mono audio is taken
|
|
|
|
from the left channel. Note, that the sck and ws pins are connected to the TX
|
|
|
|
signals of the I2S bus. That is intentional, since at the MW8960 codec these
|
|
|
|
signals are shared for RX and TX.
|
|
|
|
|
|
|
|
Example using the Teensy audio shield::
|
|
|
|
|
|
|
|
from machine import I2C, I2S, Pin
|
|
|
|
from sgtl5000 import CODEC
|
|
|
|
i2s = I2S(1, sck=Pin(21), ws=Pin(20), sd=Pin(7), mck=Pin(23),
|
|
|
|
mode=I2S.TX, bits=16,rate=44100,format=I2S.STEREO,
|
|
|
|
ibuf=40000,
|
|
|
|
)
|
|
|
|
|
|
|
|
# configure the SGTL5000 codec
|
|
|
|
i2c = I2C(0, freq=400000)
|
|
|
|
codec = CODEC(0x0A, i2c)
|
|
|
|
codec.mute_dac(False)
|
|
|
|
codec.dac_volume(0.9, 0.9)
|
|
|
|
codec.headphone_select(0)
|
|
|
|
codec.mute_headphone(False)
|
|
|
|
codec.volume(0.7, 0.7)
|
|
|
|
|
|
|
|
i2s.write(buf) # write buffer of audio samples to I2S device
|
|
|
|
|
|
|
|
The SGTL5000 codec used by the Teensy Audio shield uses the RX signals for both
|
|
|
|
RX and TX. Note that the codec is initialized after the I2S device. That is
|
|
|
|
essential since MCK is needed for its I2C operation and is provided by the I2S
|
|
|
|
controller.
|
|
|
|
|
|
|
|
MIMXRT boards may have 1 or 2 I2S buses available at the board connectors.
|
2022-04-08 12:20:44 +00:00
|
|
|
On MIMXRT1010 devices the bus numbers are 1 and 3. The I2S signals have
|
|
|
|
fixed assignments to GPIO pins. For the assignment of Pins to I2S signals,
|
|
|
|
refer to :ref:`I2S pinout <mimxrt_i2s_pinout>`.
|
2021-06-18 15:12:44 +00:00
|
|
|
|
|
|
|
Real time clock (RTC)
|
|
|
|
---------------------
|
|
|
|
|
|
|
|
See :ref:`machine.RTC <machine.RTC>`::
|
|
|
|
|
|
|
|
from machine import RTC
|
|
|
|
|
|
|
|
rtc = RTC()
|
|
|
|
rtc.datetime((2017, 8, 23, 1, 12, 48, 0, 0)) # set a specific date and time
|
|
|
|
rtc.datetime() # get date and time
|
|
|
|
rtc.now() # return date and time in CPython format.
|
|
|
|
|
|
|
|
The i.MXRT MCU supports battery backup of the RTC. By connecting a battery of
|
|
|
|
1.5-3.6V, time and date are maintained in the absence of the main power. The
|
|
|
|
current drawn from the battery is ~20µA, which is rather high. A CR2032 coin
|
|
|
|
cell will last for about one year.
|
|
|
|
|
|
|
|
SD card
|
|
|
|
-------
|
|
|
|
|
|
|
|
See :ref:`machine.SDCard <machine.SDCard>`::
|
|
|
|
|
|
|
|
import machine, os
|
|
|
|
|
|
|
|
sd = machine.SDCard()
|
|
|
|
fs = os.VfsFat(sd)
|
|
|
|
os.mount(fs, "/sd") # mount
|
|
|
|
os.listdir('/sd') # list directory contents
|
|
|
|
os.umount('/sd') # eject
|
|
|
|
|
|
|
|
Note: The i.mx-rt 1011 and 1015 based boards do not support the ``machine.SDCard``
|
|
|
|
class. For these, the SPI based driver ``sdcard.py`` from the MicroPython drivers
|
|
|
|
can be used. When using it, you have to overdrive the CS pin of the SPI hardware
|
|
|
|
module. Example::
|
|
|
|
|
|
|
|
import os, sdcard, machine
|
|
|
|
|
|
|
|
cs_pin = "D10"
|
|
|
|
spi = machine.SPI(0) # SPI0 with cs at Pin "D10" used for SDCARD
|
|
|
|
cs = machine.Pin(cs_pin, machine.Pin.OUT, value=1)
|
|
|
|
sd = sdcard.SDCard(spi, cs)
|
|
|
|
vfs = os.VfsFat(sd)
|
|
|
|
os.mount(vfs, "/sdcard")
|
|
|
|
|
|
|
|
OneWire driver
|
|
|
|
--------------
|
|
|
|
|
|
|
|
The OneWire driver is implemented in software and works on all pins::
|
|
|
|
|
|
|
|
from machine import Pin
|
|
|
|
import onewire
|
|
|
|
|
|
|
|
ow = onewire.OneWire(Pin(12)) # create a OneWire bus on GPIO12
|
|
|
|
ow.scan() # return a list of devices on the bus
|
|
|
|
ow.reset() # reset the bus
|
|
|
|
ow.readbyte() # read a byte
|
|
|
|
ow.writebyte(0x12) # write a byte on the bus
|
|
|
|
ow.write('123') # write bytes on the bus
|
|
|
|
ow.select_rom(b'12345678') # select a specific device by its ROM code
|
|
|
|
|
|
|
|
There is a specific driver for DS18S20 and DS18B20 devices::
|
|
|
|
|
|
|
|
import time, ds18x20
|
|
|
|
ds = ds18x20.DS18X20(ow)
|
|
|
|
roms = ds.scan()
|
|
|
|
ds.convert_temp()
|
|
|
|
time.sleep_ms(750)
|
|
|
|
for rom in roms:
|
|
|
|
print(ds.read_temp(rom))
|
|
|
|
|
|
|
|
Be sure to put a 4.7k pull-up resistor on the data line. Note that
|
|
|
|
the ``convert_temp()`` method must be called each time you want to
|
|
|
|
sample the temperature.
|
|
|
|
|
|
|
|
DHT driver
|
|
|
|
----------
|
|
|
|
|
|
|
|
The DHT driver is implemented in software and works on all pins::
|
|
|
|
|
|
|
|
import dht
|
|
|
|
import machine
|
|
|
|
|
|
|
|
d = dht.DHT11(machine.Pin(4))
|
|
|
|
d.measure()
|
|
|
|
d.temperature() # eg. 23 (°C)
|
|
|
|
d.humidity() # eg. 41 (% RH)
|
|
|
|
|
|
|
|
d = dht.DHT22(machine.Pin(4))
|
|
|
|
d.measure()
|
|
|
|
d.temperature() # eg. 23.6 (°C)
|
|
|
|
d.humidity() # eg. 41.3 (% RH)
|
|
|
|
|
|
|
|
Be sure to have a 4.7k pull-up resistor on the data line. Some
|
|
|
|
DHT modules may already have one.
|
|
|
|
|
|
|
|
Ethernet driver
|
|
|
|
---------------
|
|
|
|
|
|
|
|
All MIMXRT boards except the MIMXRT1011 based boards and Teensy 4.0 support
|
|
|
|
Ethernet. Example usage::
|
|
|
|
|
|
|
|
import network
|
|
|
|
|
|
|
|
lan = network.LAN(0)
|
|
|
|
lan.active(True)
|
|
|
|
|
|
|
|
If there is a DHCP server in the LAN, the IP address is supplied by that server.
|
|
|
|
Otherwise, the IP address can be set with lan.ifconfig(). The default address
|
|
|
|
is 192.168.0.1.
|
|
|
|
|
|
|
|
Teensy 4.1 does not have an Ethernet jack on the board, but PJRC offers an
|
|
|
|
adapter for self-assembly. The Seeed ARCH MIX board has no PHY hardware on the
|
|
|
|
board, however you can attach external PHY interfaces. By default, the firmware
|
|
|
|
for Seeed Arch Mix uses the driver for a LAN8720 PHY. The MIMXRT1170_EVK is
|
|
|
|
equipped with two Ethernet ports, which are addressed as LAN(0) for the 100M
|
|
|
|
port and LAN(1) for the 1G port.
|
|
|
|
|
|
|
|
For details of the network interface refer to the class :ref:`network.LAN <network.LAN>`.
|
|
|
|
|
|
|
|
Transferring files
|
|
|
|
------------------
|
|
|
|
|
|
|
|
Files can be transferred to the i.MXRT devices for instance with the ``mpremote``
|
|
|
|
tool or using an SD card. If Ethernet is available, you can also use ftp.
|
|
|
|
See the MicroPython forum for the FTP server or other community-supported
|
|
|
|
alternatives to transfer files to an i.MXRT board, like rshell or Thonny.
|