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Christian Mauderer
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user/bsps/arm/imxrt.rst
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user/bsps/arm/imxrt.rst
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.. SPDX-License-Identifier: CC-BY-SA-4.0
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.. Copyright (C) 2020 embedded brains GmbH
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.. Copyright (C) 2020 Christian Mauderer
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imxrt (NXP i.MXRT)
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==================
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This BSP offers only one variant, the `imxrt1052`. This variant supports the
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i.MXRT 1052 processor on a IMXRT1050-EVKB (tested with rev A1). You can also
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configure it to work with custom boards.
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Build Configuration Options
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---------------------------
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Please see the documentation of the `IMXRT_*` and `BSP_*` configuration options
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for that. You can generate a default set of options with::
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./waf bsp_defaults --rtems-bsps=arm/imxrt1052 > config.ini
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Boot Process
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------------
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There are two possible boot processes supported:
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1) The ROM code loads a configuration from HyperFlash (connected to FlexSPI),
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does some initialization (based on device configuration data (DCD)) and then
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starts the application. This is the default case. `linkcmds.flexspi` is used
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for this case.
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2) Some custom bootloader does the basic initialization, loads the application
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to SDRAM and starts it from there. Select the `linkcmds.sdram` for this.
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For programming the HyperFlash in case 1, you can use the on board debugger
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integrated into the IMXRT1050-EVKB. You can generate a flash image out of a
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compiled RTEMS application with for example::
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arm-rtems6-objcopy -O binary build/arm/imxrt1052/testsuites/samples/hello.exe hello.bin
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Then just copy the generated binary to the mass storage provided by the
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debugger. Wait a bit till the mass storage vanishes and re-appears. After that,
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reset the board and the newly programmed application will start.
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For debugging: Create a special application with a `while(true)` loop at end of
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`bsp_start_hook_1`. Load that application into flash. Then remove the loop
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again, build your BSP for SDRAM and use a debugger to load the application into
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SDRAM after the BSP started from flash did the basic initialization.
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Flash Image
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-----------
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For booting from a HyperFlash (or other storage connected to FlexSPI), the ROM
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code of the i.MXRT first reads some special flash header information from a
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fixed location of the connected flash device. This consists of the Image vector
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table (IVT), Boot data and Device configuration data (DCD).
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In RTEMS, these flash headers are generated using some C-structures. If you use
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a board other than the IMXRT1050-EVKB, those structures have to be adapted. To
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do that re-define the following variables in your application (you only need the
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ones that need different values):
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.. code-block:: c
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#include <bsp/flash-headers.h>
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const uint8_t imxrt_dcd_data[] =
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{ /* Your DCD data here */ };
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const ivt imxrt_image_vector_table =
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{ /* Your IVT here */ };
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const BOOT_DATA_T imxrt_boot_data =
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{ /* Your boot data here */ };
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const flexspi_nor_config_t imxrt_flexspi_config =
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{ /* Your FlexSPI config here */ };
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You can find the default definitions in `bsps/arm/imxrt/start/flash-*.c`. Take a
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look at the `i.MX RT1050 Processor Reference Manual, Rev. 4, 12/2019` chapter
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`9.7 Program image` for details about the contents.
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FDT
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---
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The BSP used a FDT based initialization. The FDT is linked into the application.
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You can find the default FDT used in the BSP in
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`bsps/arm/imxrt/dts/imxrt1050-evkb.dts`. To use your own FDT compile it and
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convert it into a C file with (replace `YOUR.dts` and simmilar with your FDT
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source names)::
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sh> export BSP_DIR="${RTEMS_SRC_DIR}/bsps/arm/imxrt/"
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sh> arm-rtems6-cpp -P -x assembler-with-cpp \
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-I "${BSP_DIR}/include/" \
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-include "YOUR.dts" /dev/null | \
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dtc -@ -O dtb -o "YOUR.dtb" -b 0 -p 1024
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sh> rtems-bin2c -C -N imxrt_dtb "YOUR.dtb" "YOUR.c"
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Make sure that your new c file is compiled and linked into the application.
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Clock Driver
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------------
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The clock driver uses the generic `ARMv7-M Clock`.
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IOMUX
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-----
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The i.MXRT IOMUXC is initialized based on the FDT. For that, the `pinctrl-0`
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fields of all devices with a status of `ok` or `okay` will be parsed.
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Console Driver
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--------------
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LPUART drivers are registered based on the FDT. The special `rtems,path`
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attribute defines where the device file for the console is created.
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The `stdout-path` in the `chosen` node determines which LPUART is used for the
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console.
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I2C Driver
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----------
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I2C drivers are registered based on the FDT. The special `rtems,path` attribute
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defines where the device file for the I2C bus is created.
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Limitations:
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* Only basic I2C is implemented. This is mostly a driver limitation and not a
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hardware one.
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SPI Driver
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----------
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SPI drivers are registered based on the FDT. The special `rtems,path` attribute
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defines where the device file for the SPI bus is created.
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Note that the SPI-pins on the evaluation board are shared with the SD card.
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Populate R278, R279, R280, R281 on the IMXRT1050-EVKB (Rev A) to use the SPI
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pins on the Arduino connector.
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Limitations:
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* Only a basic SPI driver is implemented. This is mostly a driver limitation and
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not a hardware one.
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Network Interface Driver
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------------------------
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The network interface driver is provided by the `libbsd`. It is initialized
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according to the device tree.
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Note on the hardware: The i.MXRT1050 EVKB maybe has a wrong termination of the
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RXP, RXN, TXP and TXN lines. The resistors R126 through R129 maybe shouldn't be
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populated because the used KSZ8081RNB already has an internal termination.
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Ethernet does work on short distance anyway. But keep it in mind in case you
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have problems. Source:
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https://community.nxp.com/t5/i-MX-RT/Error-in-IMXRT1050-EVKB-and-1060-schematic-ethernet/m-p/835540#M1587
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NXP SDK files
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-------------
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A lot of peripherals are currently not yet supported by RTEMS drivers. The NXP
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SDK offers drivers for these. For convenience, the BSP compiles the drivers from
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the SDK. But please note that they are not tested and maybe won't work out of
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the box. Everything that works with interrupts most likely needs some special
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treatment.
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Caveats
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-------
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The clock configuration support is quite rudimentary. The same is true for
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SDRAM. It mostly relies on the DCD and on a static clock configuration that is
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taken from the NXP SDK example projects.
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The MPU settings are currently quite permissive.
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There is no power management support.
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@ -14,6 +14,7 @@ arm (ARM)
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.. include:: arm/edb7312.rst
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.. include:: arm/gumstix.rst
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.. include:: arm/imx.rst
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.. include:: arm/imxrt.rst
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.. include:: arm/lm3s69xx.rst
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.. include:: arm/lpc176x.rst
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.. include:: arm/imx.rst
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