README
======

This directory contains the port of NuttX to the Beaglebone Black board
See http://beagleboard.org for information about Beaglebone Black. This
board is based around the TI AM335x Sitara Cortex-A8 CPU.
This port was developed on the rev. C of the board:

Beaglebone Black (See http://beagleboard.org/black)

ITEMS DETAILS
-------------------- ---------------------------------------------------
CPU 1GHz ARM Cortex-A8
GPU SG530 3D, 20M Polygons/S
DRAM 512MB DDR3 800MHz
Onboard Storage 4GB, 8bit Embedded MMC, microSD card (TF) slot for up to 32GB
Video Output HDMI
Extension Interface 2.54mm Headers, 92 pins
Network interface 10/100Mbps RJ45
Power 5V, 1000mA
Overall Size 3.4" X 2.15"

Main features of the TI AM335x Sitara
(See http://www.ti.com/product/am3358):

CPU
- ARM Cortex-A8
- 32KB I-Cache
- 32KB D-Cache
- 256KB L2 Cache with ECC

FPU
- NEON SIMD Coprocessor

Memory
- 176KB of On-Chip Boot ROM
- 64KB of Dedicated RAM
- 64KB of General-Purpose On-Chip Memory Controller (OCMC) RAM
- 16-bit DDR2/DDR3
- Memory capacity up to 8G bits
- 8-Bit and 16-Bit Asynchronous Memory Interface with up to Seven Chip Selects (NAND, NOR, Muxed-NOR, SRAM)

Boot Devices
- NAND Flash
- SPI NOR Flash
- SD Card
- UART

TODO:

Contents
========

- Beaglebone black Rev.C Connectors
- Serial Console
- LEDs
- Buttons
- JTAG
- Booting NuttX from an SD card
- Configurations

Beaglebone black Rev.C Connectors
=====================

Serial Console
==============

By default, the serial console will be provided on UART0 in all of these
configurations.

UART0 is available on the 6-pin Debug connector:

Pin 1: GND
Pin 2: N/C
Pin 3: N/C
Pin 4: B_UART0_RX / UART0_RX / PIN E15
Pin 5: B_UART0_TX / UART0_TX / PIN E16
Pin 6: N/C

PIN E16: UART0_TXD/SPI1_CS1/DCAN0_RX/I2C2_SCL/ECAP1_IN_PWM1_OUT/
PR1_PRU1_PRU_R30_15/PR1_PRU1_PRU_R31_15/GPIO1_11
PIN E15: UART0_RXD/SPI1_CS0/DCAN0_TX/I2C2_SDA/ECAP2_IN_PWM2_OUT/
PR1_PRU1_PRU_R30_14/PR1_PRU1_PRU_R31_14/GPIO1_10
LEDs
====

The Beaglebone black Rev. C has four blue LEDs; three can be controlled from software.
Two are tied to ground and, hence, illuminated by driving the output pins to a high
value:

1. LED0 GPMC_A5 GPMC_A5/GMII2_TXD0/RGMII2_TD0/RMII2_TXD0/GPMC_A21/
PR1_MII1_RXD3/eQEP1B_IN/GPIO1_21
2. LED1 GPMC_A6 GPMC_A6/GMII2_TXCLK/RGMII2_TCLK/MMC2_DAT4/GPMC_A22/
PR1_MII1_RXD2/eQEP1_INDEX/GPIO1_22
3. LED2 GPMC_A7 GPMC_A7/GMII2_RXCLK/RGMII2_RCLK/MMC2_DAT5/GPMC_A23/
PR1_MII1_RXD1/eQEP1_STROBE/GPIO1_23
4. LED3 GPMC_A8 GPMC_A8/GMII2_RXD3/RGMII2_RD3/MMC2_DAT6/GPMC_A24/
PR1_MII1_RXD0/MCASP0_ACLKX/GPIO1_24

These LEDs are not used by the board port unless CONFIG_ARCH_LEDS is
defined. In that case, the usage by the board port is defined in
include/board.h and src/am335x_leds.c. The LEDs are used to encode OS-related
events as follows:

SYMBOL Meaning LED state
LED1 LED3 LED4
----------------- ----------------------- ---- ---- ------------
LED_STARTED NuttX has been started ON OFF OFF
LED_HEAPALLOCATE Heap has been allocated OFF ON OFF
LED_IRQSENABLED Interrupts enabled ON ON OFF
LED_STACKCREATED Idle stack created ON ON OFF
LED_INIRQ In an interrupt N/C N/C Soft glow
LED_SIGNAL In a signal handler N/C N/C Soft glow
LED_ASSERTION An assertion failed N/C N/C Soft glow
LED_PANIC The system has crashed N/C N/C 2Hz Flashing
LED_IDLE MCU is is sleep mode Not used

After booting, LED1 and 3 are not longer used by the system and can be used for
other purposes by the application (Of course, all LEDs are available to the
application if CONFIG_ARCH_LEDS is not defined.

Buttons
=======

JTAG
====

Booting NuttX from an SD card
=============================

These are the steps to get U-Boot booting from SD Card:

1. Configure and build the NuttX Beaglebone Black configuration. You
should have a file alled nuttx.bin when the build completes.

2. Insert a FLASH stick into the host PC and format it for FAT32 FS.

3. Copy nuttx.bin into FLASH stick root.

4. Remove the FLASH stick from the host PC. Insert into the Beaglebone
Black microSD slot.

5. Connect a RS-232 Converted or USB serial adapter onto the Beaglebone
Black board and open a serial terminal on the host PC to communicate
with the target.

6. Reset the Stop Beaglebone Black boot. You should see output from
U-boot in the serial console. Stop the normal boot-up sequence
after the U-Boot prompt before Linux is started.:

Hit any key to stop autoboot: 0
U-Boot#

7. Load Nuttx into memory from the U-Boot prompt and run

U-Boot# load mmc 0 0x8a000000 nuttx.bin
U-Boot# go 0x8a000000

If your are running the 'nsh' configuration you then should see:

NuttShell (NSH)
nsh>

Configurations
==============

Information Common to All Configurations
----------------------------------------
Each Beaglebone Black configuration is maintained in a sub-directory and
can be selected as follow:

tools/configure.sh [OPTIONS] beaglebone-black/

Where [OPTIONS] include -l to configure for a Linux host platform and
-c means to configure for a Windows Cygwin host platform. -h will give
you the list of all options.

Before building, make sure the PATH environment variable includes the
correct path to the directory than holds your toolchain binaries.

And then build NuttX by simply typing the following. At the conclusion of
the make, the nuttx binary will reside in an ELF file called, simply, nuttx.

make

The that is provided above as an argument to the tools/configure.sh
must be is one of the following.

NOTES:

1. These configurations use the mconf-based configuration tool. To
change any of these configurations using that tool, you should:

a. Build and install the kconfig-mconf tool. See nuttx/README.txt
see additional README.txt files in the NuttX tools repository.

b. Execute 'make menuconfig' in nuttx/ in order to start the
reconfiguration process.

2. Unless stated otherwise, all configurations generate console
output on UART0.

3. All of these configurations use the Code Sourcery for Windows toolchain
(unless stated otherwise in the description of the configuration). That
toolchain selection can easily be reconfigured using 'make menuconfig'.
Here are the relevant current settings:

Build Setup:
CONFIG_HOST_WINDOWS=y : Microsoft Windows
CONFIG_WINDOWS_CYGWIN=y : Using Cygwin or other POSIX environment

System Type -> Toolchain:
CONFIG_ARMV7A_TOOLCHAIN_CODESOURCERYW=y : CodeSourcery for Windows

Configuration Sub-directories
-----------------------------

nsh:

This configuration directory provide the NuttShell (NSH). There are

STATUS:
2019-01-06: Work in progress. Till now it is possible to pass arm_boot(), but
Prefetch abort is met when devnull_register() call is done. Have no idea why.
I was able to trace down to _inode_search() call. If I put any debug statement
like "up_lowputc('0');" right after "desc->node = node;" statement at line 425
the code does not crash.
2019-01-09: The NSH configuration is now functional.
2019-01-16: Correct timer interrupts by switching to DMTimer2 (DMTimer1ms is
not initialized by U-Boot).