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
96Boards Meerkat96

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/arm/96b_meerkat96/96b_meerkat96_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 Meerakat96 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/arm/96b_meerkat96/96b_meerkat96.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:

  1. Put the M4 core in reset
  2. Load the binary in the appropriate addr (TMCL, TCMU, OCRAM, OCRAM_S or DDR)
  3. Set PC (Program Counter)
  4. Set SP (Stack Pointer)
  5. 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 Build an Application and Run an Application for more details).