i.MX RT

The i.MX RT series of chips from NXP Semiconductors is based around an ARM Cortex-M7 core running at 500 MHz, 600 MHz or 1 GHz based on particular MCUs

Supported MCUs

The following list includes MCUs from i.MX RT series and indicates whether they are supported in NuttX

MCU

Support

Core

Frequency

RT500

No

Cortex-M33

200 MHz

RT600

No

Cortex-M33

300 MHz

RT1010

No

Cortex-M7

500 MHz

RT1015

No

Cortex-M7

500 MHz

RT1020

Yes

Cortex-M7

500 MHz

RT1024

No

Cortex-M7

500 MHz

RT1050

Yes

Cortex-M7

600 MHz

RT1060

Yes

Cortex-M7

600 MHz

RT1064

Yes

Cortex-M7

600 MHz

RT1170

No

Cortex-M7 + M4

1 GHz + 400 MHz

Data and Instruction Cache

MCUs i.MX RT1010 and higher have separated caches for instructions and data. Data cache is initially set as write-through but can be changed to write-back via Kconfig. While write-back gives better 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 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 divided by the prescaler value from 1 to 4096. Possible values for CONFIG_USEC_PER_TICK are 10 or 100 for example.

Peripheral Support

The following list indicates peripherals supported in NuttX:

Peripheral

Support

ACMP

No

ADC

Yes

CAN

Yes

CSI

No

DAC

No

eLCDIF

Yes

ENC

Yes

ENET

Yes

FlexIO

No

GPIO

Yes

I2S

Yes

PWM

Yes

SAI

No

SPDIF

No

SPI

Yes

UART

Yes

USB

Yes

ACMP

The circout for comparing two analog input voltages designed to operate across the full range of supply voltage (rail-to-rail operation).

ADC

ADC driver with the successive approximation analog/digital converter. The lower-half of this driver is initialize by calling imxrt_adcinitialize().

ADC module can use either continous trigger (next conversion is started as soon as the previous is finished) or hardware trigger. This option is selected by IMXRT_ADCx_ETC (x = 1, 2) config option. If IMXRT_ADCx_ETC = -1 then continous trigger is used. If corresponding XBAR number is put in IMXRT_ADCx_ETC then that signal is used to trigger the ADC conversion (for example PWM signal can be used as a source). For PWM XBAR options please refer to PWM chapter of this documentation.

Hardware triggering is currently limited to maximum of 8 channels. HW trigger is automatically disabled if there are more than 8 channels.

DMA is currently not supported for ADC modules.

CAN

FlexCAN driver is supported in MCUs i.MX RT1020 and higher. i.MX RT106x have both classical CAN and also one CAN FD while i.MX RT1170 have 3 CAN FD peripherals. FlexCAN driver in imxrt works beyond SocketCAN driver layout. The lower-half of this driver is initialize by calling imxrt_cannitialize().

There is an booting option that automatically provides initialization of network interface in the early stages of booting and therefore calling imxrt_cannitialize() via board specific logic is not necessary. This however works only when there is only one interface in the chip. For running more interfaces (like CAN and Ethernet), network late initialization must be turn on by CONFIG_NETDEV_LATEINIT and board specific logic must call lower-half part of drivers.

CSI

CMOS Sensor interface which enables the chip to connect directly to external CMOS image sensors.

DAC

Digital/analog converter for external signal is only supported in i.MX RT1170 MCU. It is 12 bit lower power, general purpose DAC.

eLCDIF

The enhanced Liquid Crystal Display interface (LCDIF) is a general purpose display controller.

ENC

The enhanced quadrature encoder/decoder module supported in i.MX RT1015 and higher. The lower-half of this driver is initialize by calling imxrt_qeinitialize().

ENET

Ethernet driver supported in i.MX RT1020 and higher. The lower-half of this driver is initialize by calling imxrt_netnitialize().

There is an booting option that automatically provides initialization of network interface in the early stages of booting and therefore calling imxrt_cannitialize() via board specific logic is not necessary. This however works only when there is only one interface in the chip. For running more interfaces (like CAN and Ethernet), network late initialization must be turn on by CONFIG_NETDEV_LATEINIT and board specific logic must call lower-half part of drivers.

FlexIO

A configurable module providing a range of functionality like emulation of a variety of serial/parallel communication protocols, flexible 16-bit timers or programmable logic blocks. This module is supported in i.MX RT1010 and higher.

GPIO

Pins can be configured using imxrt_config_gpio() function. Writing to pins is done by imxrt_gpio_write() function and reading is done by imxrt_gpio_read().

MCUs i.MX RT1060 and higher includes both standard speed GPIOs (1-5) and high speed GPIOS (6-9). Regular and high speed GPIO share the same pins (GPIO1 is with GPIO6 etc), therefore IOMUXC_GPR_GPR26-29 registers are used to determine what module is used for the GPIO pins.

I2C

Inter-Integrated Circout module supporting an interface to an I2C bus as master and/or as a slave. The lower-half of this driver is initialize by calling imxrt_i2cbus_initialize().

PWM

Pulse width modulator supported in i.MX RT1010 and higher. Multiple channels option is evailable. Output on pin B is currently supported only as a complementary option to pin A. The lower-half of this driver is initialize by calling imxrt_pwminitialize().

PWM module can be synchronized by an external signal. The external signal used for synchronization is selected by IMXRT_FLEXPWMx_MODx_SYNC_SRC config option. The number in IMXRT_FLEXPWM4_MOD4_SYNC_SRC corresponds with the XBAR number. Following numbers can be used for synchronization of PWMs with other PWM module when using iMXRT1020, iMXRT1050 or iMXRT1060.

  • PWM1 Module 1 = 40

  • PWM1 Module 2 = 41

  • PWM1 Module 3 = 42

  • PWM1 Module 4 = 43

  • PWM2 Module 1 = 44

  • PWM2 Module 2 = 45

  • PWM2 Module 3 = 46

  • PWM2 Module 4 = 47

  • PWM3 Module 1 = 48

  • PWM3 Module 2 = 49

  • PWM3 Module 3 = 50

  • PWM3 Module 4 = 51

  • PWM4 Module 1 = 52

  • PWM4 Module 2 = 53

  • PWM4 Module 3 = 54

  • PWM4 Module 4 = 55

iMXRT1170 has different XBAR connections:

  • PWM1 Module 1 = 74

  • PWM1 Module 2 = 75

  • PWM1 Module 3 = 76

  • PWM1 Module 4 = 77

  • PWM2 Module 1 = 78

  • PWM2 Module 2 = 79

  • PWM2 Module 3 = 80

  • PWM2 Module 4 = 81

  • PWM3 Module 1 = 82

  • PWM3 Module 2 = 83

  • PWM3 Module 3 = 84

  • PWM3 Module 4 = 85

  • PWM4 Module 1 = 86

  • PWM4 Module 2 = 87

  • PWM4 Module 3 = 88

  • PWM4 Module 4 = 89

SAI

Synchronous audio interface provided by I2C module. Supported in i.MX RT1015 and higher.

SPDIF

Sony/Philips digital interface audio block. It is a stereo transceiver that allows the processor to receive and transmit digital audio. Supported in i.MX RT1010 and higher.

SPI

Serial Peripheral interface module that supports an interface to an SPI bus as a master and/or a slave. The lower-half of this driver is initialize by calling imxrt_lpsibus_initialize().

UART

Universal Asynchronous Receiver/Transmitter module. UART is initialized automatically during MCU boot.

USB

Console communication over USB is supported via CDC-ACM. Only USB Device is currently supported for i.MX RT in NuttX

Supported Boards