VAR-SOM-MX7 FreeRTOS for M4
Prerequisites
Before starting, prepare a boot SD with your Yocto Morty build for VAR-SOM-MX7
Installing required packages
Download and install GNU-ARM bare-metal toolchain:
mkdir ~/var-som-mx7_m4-freertos cd ~/var-som-mx7_m4-freertos wget https://developer.arm.com/-/media/Files/downloads/gnu-rm/5_4-2016q3/gcc-arm-none-eabi-5_4-2016q3-20160926-linux.tar.bz2 tar xvf gcc-arm-none-eabi-5_4-2016q3-20160926-linux.tar.bz2
Download FreeRTOS BSP for the SOM:
cd ~/var-som-mx7_m4-freertos git clone https://github.com/varigit/freertos-variscite.git -b freertos_bsp_1.0.1_imx7d-var01 cd freertos-variscite
Documentation
Original NXP documentation is available in the following folder:
~/var-som-mx7_m4-freertos/freertos-variscite/doc
Available demos
All of the Variscite examples are located under the following folder
~/var-som-mx7_m4-freertos/freertos-variscite/examples/var-som-mx7_m4
The available demos for VAR-SOM-MX7 are
| path |
memory type |
|---|---|
| demo_apps/blinking_imx_demo | TCM |
| demo_apps/hello_world | TCM |
| demo_apps/hello_world_ddr | DDR |
| demo_apps/hello_world_ocram | OCRAM |
| demo_apps/low_power_imx7d/rand_wfi | TCM |
| demo_apps/rpmsg/pingpong_bm | TCM |
| demo_apps/rpmsg/pingpong_freertos | TCM |
| demo_apps/rpmsg/str_echo_bm | TCM |
| demo_apps/rpmsg/str_echo_freertos | TCM |
| demo_apps/sema4_demo | TCM |
| driver_examples/adc_imx7d | TCM |
| driver_examples/flexcan/flexcan_loopback | TCM |
| driver_examples/flexcan/flexcan_network | TCM |
| driver_examples/gpio_imx | TCM |
| driver_examples/gpt | TCM |
| driver_examples/i2c_imx/i2c_interrupt_rtc_imx7d | TCM |
| driver_examples/i2c_imx/i2c_polling_rtc_imx7d | TCM |
| driver_examples/uart_imx/uart_interrupt | TCM |
| driver_examples/uart_imx/uart_polling | TCM |
| driver_examples/wdog_imx | TCM |
Almost all of the above demos are also available for iMX7 SabreSD.
You can build and run the demos following official NXP documentation for iMX7 SabreSD.
Memory types
The BSP allow linking using 3 different memory types: DDR, OCRAM, TCM.
Almost all the demos are provided for TCM.
Here is available a short description of them.
DDR
Part of the DDR address qare reserved to CortexM4 in Linux dts.
When linking for DDR, the application must be loaded in that DDR space (max 32kB for code and 32kB for data).
Related linker file can be found here:
~/var-som-mx7_m4-freertos/freertos-variscite/platform/devices/MCIMX7D/linker/gcc/MCIMX7D_M4_ddr.ld
OCRAM
iMX7 include an OnChip RAM.
When linking for OCRAM, the application must be loaded in that OCRAM space (max 32kB for code and 32kB for data).
Related linker file can be found here:
~/var-som-mx7_m4-freertos/freertos-variscite/platform/devices/MCIMX7D/linker/gcc/MCIMX7D_M4_ocram.ld
TCM
Cortex-M4 include an Tightly Coupled Memory.
When linking for TCM, the application must be loaded in that TCM space (max 32kB for code and 32kB for data).
Related linker file can be found here:
~/var-som-mx7_m4-freertos/freertos-variscite/platform/devices/MCIMX7D/linker/gcc/MCIMX7D_M4_tcm.ld
Special notes about I2C demos
Since we have no on-board sensors, under "driver_examples/i2c_imx" you will find 2 demos accessing the RTC.
The demos require disabling I2C2 from Linux dts. This also means that both WM8731 and OV5640 cannot be controlled on Linux side.
However this BSP aims to provide examples for testing, so if not needed, feel free to re-enable it on Linux side.
If you plan to use a different I2C bus for M4, just disable it in Linux dts and update I2C section in file:
~/var-som-mx7_m4-freertos/freertos-variscite/examples/var-som-mx7_m4/board.h
Building a demo
For any demo just follow this steps:
cd ~/var-som-mx7_m4-freertos/freertos-variscite/examples/var-som-mx7_m4 cd <demo_folder> cd armgcc export ARMGCC_DIR=~/var-som-mx7_m4-freertos/gcc-arm-none-eabi-5_4-2016q3 ./build_all.sh > /dev/null
Then copy the ".bin" in the FAT32 partition of the boot SD.
Running a demo
A detailed step by step procedure to running each of the demos is available in the document
~/var-som-mx7_m4-freertos/freertos-variscite/doc/FreeRTOS_BSP_for_i.MX_7Dual_Demo_User’s_Guide.pdf
Binary demos must be loaded accord the memory type used for linking.
For all memory types the steps are the same, just the addresses are different
load application image to memory flush content to memory start Cortex-M4 from memory
DDR
fatload mmc 0:1 0x9FF00000 demo_ddr.bin dcache flush bootaux 0x9FF00000
OCRAM
fatload mmc 0:1 0x00910000 demo_ocram.bin dcache flush bootaux 0x00910000
TCM
fatload mmc 0:1 0x007F8000 demo_tcl.bin dcache flush bootaux 0x007F8000
Debugging a demo
The only way currently supported to debug applications is using Lauterbach and Trace32.
The script to attach Trace 32 is available here:
~/var-som-mx7_m4-freertos/freertos-variscite/tools/trace32/attach_imx7d_m4.cmm
Further details are available at paragraph 7 of official NXP documentation:
~/var-som-mx7_m4-freertos/freertos-variscite/doc/Getting_Started_with_FreeRTOS_BSP_for_i.MX_7Dual.pdf