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96Boards Meerkat96

Overview

96Boards Meerkat96 board is based on NXP i.MX7 Hybrid multi-core processor, composed of a dual Cortex®-A7 and a single Cortex®-M4 core. Zephyr OS is ported to run on the Cortex®-M4 core.

Board features:
- RAM: 512 Mbyte
- Storage:
  - microSD Socket
- Wireless:
  - WiFi: 2.4GHz IEEE 802.11b/g/n
  - Bluetooth: v4.1 (BR/EDR)
- USB:
  - Host - 2x type A
  - OTG: - 1x type micro-B
- HDMI
- Connectors:
  - 40-Pin Low Speed Header
  - 60-Pin High Speed Header
- LEDs:
  - 4x Green user LEDs
  - 1x Blue Bluetooth LED
  - 1x Yellow WiFi LED

More information about the board can be found at the 96Boards website.

Hardware

The i.MX7 SoC provides the following hardware capabilities:

Dual Cortex A7 (800MHz/1.0GHz) core and Single Cortex M4 (200MHz) core
Memory
- External DDR memory up to 1 Gbyte
- Internal RAM -> A7: 256KB SRAM
- Internal RAM -> M4: 3x32KB (TCML, TCMU, OCRAM_S), 1x128KB (OCRAM) and 1x256MB (DDR)
Display
- RGB 1920x1080x24bpp
- 4-wire Resistive touch
Multimedia
- 1x Camera Parallel Interface
- 1x Analog Audio Line in (Stereo)
- 1x Analog Audio Mic in (Mono)
- 1x Analog Audio Headphone out (Stereo)
Connectivity
- USB 2.0 OTG (High Speed)
- USB 2.0 host (High Speed)
- 10/100 Mbit/s Ethernet PHY
- 4x I2C
- 4x SPI
- 7x UART
- 1x IrDA
- 20x PWM
- Up to 125 GPIO
- 4x Analog Input (12 Bit)
- 2x SDIO/SD/MMC (8 Bit)
- 2x CAN

More information about the i.MX7 SoC can be found here:

Supported Features

The Zephyr 96b_meerkat96 board configuration supports the following hardware features:

Interface	Controller	Driver/Component
NVIC	on-chip	nested vector interrupt controller
SYSTICK	on-chip	systick
GPIO	on-chip	gpio
UART	on-chip	serial port-polling; serial port-interrupt

The default configuration can be found in the defconfig file:

boards/96boards/meerkat96/96b_meerkat96_mcimx7d_m4_defconfig

Other hardware features are not currently supported by the port.

Connections and IOs

96Boards Meerkat96 board was tested with the following pinmux controller configuration.

Board Name	SoC Name	Usage
UART_1 RXD	UART1_TXD	UART Console
UART_1 TXD	UART1_RXD	UART Console
LED_R1	GPIO1_IO04	LED0
LED_R2	GPIO1_IO05	LED1
LED_R3	GPIO1_IO06	LED2
LED_R4	GPIO1_IO07	LED3

System Clock

The M4 Core is configured to run at a 200 MHz clock speed.

Serial Port

The iMX7D SoC has seven UARTs. UART_1 is configured for the console and the remaining are not used/tested.

Programming and Debugging

The 96Boards Meerkat96 board doesn’t have QSPI flash for the M4 and it needs to be started by the A7 core. The A7 core is responsible to load the M4 binary application into the RAM, put the M4 in reset, set the M4 Program Counter and Stack Pointer, and get the M4 out of reset. The A7 can perform these steps at bootloader level or after the Linux system has booted.

The M4 can use up to 5 different RAMs. These are the memory mapping for A7 and M4:

Region	Cortex-A7	Cortex-M4 (System Bus)	Cortex-M4 (Code Bus)	Size
DDR	0x80000000-0xFFFFFFFF	0x80000000-0xDFFFFFFF	0x10000000-0x1FFEFFFF	2048MB (less for M4)
OCRAM	0x00900000-0x0091FFFF	0x20200000-0x2021FFFF	0x00900000-0x0091FFFF	128KB
TCMU	0x00800000-0x00807FFF	0x20000000-0x20007FFF		32KB
TCML	0x007F8000-0x007FFFFF		0x1FFF8000-0x1FFFFFFF	32KB
OCRAM_S	0x00180000-0x00187FFF	0x20180000-0x20187FFF	0x00000000-0x00007FFF	32KB
QSPI Flash			0x08000000-0x0BFFFFFF	64MB

For more information about memory mapping see the i.MX 7 Dual Reference Manual (section 2.1.2 and 2.1.3), and the Toradex Wiki.

At compilation time you have to choose which RAM will be used. This configuration is done in the file boards/96boards/meerkat96/96b_meerkat96_mcimx7d_m4.dts with “zephyr,flash” (when CONFIG_XIP=y) and “zephyr,sram” properties. The available configurations are:

"zephyr,flash"
- &ddr_code
- &tcml_code
- &ocram_code
- &ocram_s_code
- &ocram_pxp_code
- &ocram_epdc_code

"zephyr,sram"
- &ddr_sys
- &tcmu_sys
- &ocram_sys
- &ocram_s_sys
- &ocram_pxp_sys
- &ocram_epdc_sys

Below you will find the instructions to load and run Zephyr on M4 from A7 using u-boot.

Copy the compiled zephyr.bin to the first FAT partition of the SD card and plug into the board. Power it up and stop the u-boot execution. Set the u-boot environment variables and run the zephyr.bin from the appropriated memory configured in the Zephyr compilation:

setenv bootm4 'fatload mmc 0:1 $m4addr $m4fw && dcache flush && bootaux $m4addr'
# TCML
setenv m4tcml 'setenv m4fw zephyr.bin; setenv m4addr 0x007F8000'
setenv bootm4tcml 'run m4tcml && run bootm4'
run bootm4tcml
# TCMU
setenv m4tcmu 'setenv m4fw zephyr.bin; setenv m4addr 0x00800000'
setenv bootm4tcmu 'run m4tcmu && run bootm4'
run bootm4tcmu
# OCRAM
setenv m4ocram 'setenv m4fw zephyr.bin; setenv m4addr 0x00900000'
setenv bootm4ocram 'run m4ocram && run bootm4'
run bootm4ocram
# OCRAM_S
setenv m4ocrams 'setenv m4fw zephyr.bin; setenv m4addr 0x00180000'
setenv bootm4ocrams 'run m4ocrams && run bootm4'
run bootm4ocrams
# DDR
setenv m4ddr 'setenv m4fw zephyr.bin; setenv m4addr 0x80000000'
setenv bootm4ddr 'run m4ddr && run bootm4'
run bootm4ddr

Debugging

96Boards Meerkat96 board can be debugged by connecting an external JLink JTAG debugger to the J4 debug connector. Then download and install J-Link Tools and NXP iMX7D Connect CortexM4.JLinkScript.

To run Zephyr Binary using J-Link create the following script in order to get the Program Counter and Stack Pointer from zephyr.bin.

get-pc-sp.sh: .. code-block:: console

#!/bin/sh

firmware=$1

pc=$(od -An -N 8 -t x4 $firmware | awk ‘{print $2;}’) sp=$(od -An -N 8 -t x4 $firmware | awk ‘{print $1;}’)

echo pc=$pc echo sp=$sp

Get the SP and PC from firmware binary: ./get-pc-sp.sh zephyr.bin .. code-block:: console

pc=00900f01 sp=00905020

Plug in the J-Link into the board and PC and run the J-Link command line tool:

/usr/bin/JLinkExe -device Cortex-M4 -if JTAG -speed 4000 -autoconnect 1 -jtagconf -1,-1 -jlinkscriptfile iMX7D_Connect_CortexM4.JLinkScript

The following steps are necessary to run the zephyr.bin:

Put the M4 core in reset
Load the binary in the appropriate addr (TMCL, TCMU, OCRAM, OCRAM_S or DDR)
Set PC (Program Counter)
Set SP (Stack Pointer)
Get the M4 core out of reset

Issue the following commands inside J-Link commander:

w4 0x3039000C 0xAC
loadfile zephyr.bin,0x00900000
w4 0x00180000 00900f01
w4 0x00180004 00905020
w4 0x3039000C 0xAA

With these mechanisms, applications for the 96b_meerkat96 board configuration can be built and debugged in the usual way (see Building an Application and Run an Application for more details).