Nucleo-L452RE README
====================

This README file discusses the port of NuttX to the STMicro Nucleo-L452RE
board. That board features the STM32L452RET6 MCU with 512KiB of FLASH
and 160KiB of SRAM.

Contents
========

- Status
- Nucleo-64 Boards
- LEDs
- Buttons
- Serial Console
- Configurations

Status
======
2017-05-04: The board now boots and the basic NSH configurations works
without problem.

Nucleo-64 Boards
================

The Nucleo-L452RE is a member of the Nucleo-64 board family. The Nucleo-64
is a standard board for use with several STM32 parts in the LQFP64 package.
Variants including:

Order code Targeted STM32
------------- --------------
NUCLEO-F030R8 STM32F030R8T6
NUCLEO-F070RB STM32F070RBT6
NUCLEO-F072RB STM32F072RBT6
NUCLEO-F091RC STM32F091RCT6
NUCLEO-F103RB STM32F103RBT6
NUCLEO-F302R8 STM32F302R8T6
NUCLEO-F303RE STM32F303RET6
NUCLEO-F334R8 STM32F334R8T6
NUCLEO-F401RE STM32F401RET6
NUCLEO-F410RB STM32F410RBT6
NUCLEO-F411RE STM32F411RET6
NUCLEO-F446RE STM32F446RET6
NUCLEO-L053R8 STM32L053R8T6
NUCLEO-L073RZ STM32L073RZT6
NUCLEO-L152RE STM32L152RET6
NUCLEO-L452RE STM32L452RET6
NUCLEO-L476RG STM32L476RGT6

LEDs
====

The Nucleo-64 board has one user controlable LED, User LD2. This green
LED is a user LED connected to Arduino signal D13 corresponding to STM32
I/O PA5 (PB13 on other some other Nucleo-64 boards).

- When the I/O is HIGH value, the LED is on
- When the I/O is LOW, the LED is off

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/stm32_autoleds.c. The LEDs are used to encode
OS-related events as follows when the red LED (PE24) is available:

SYMBOL Meaning LD2
------------------- ----------------------- -----------
LED_STARTED NuttX has been started OFF
LED_HEAPALLOCATE Heap has been allocated OFF
LED_IRQSENABLED Interrupts enabled OFF
LED_STACKCREATED Idle stack created ON
LED_INIRQ In an interrupt No change
LED_SIGNAL In a signal handler No change
LED_ASSERTION An assertion failed No change
LED_PANIC The system has crashed Blinking
LED_IDLE MCU is is sleep mode Not used

Thus if LD2, NuttX has successfully booted and is, apparently, running
normally. If LD2 is flashing at approximately 2Hz, then a fatal error
has been detected and the system has halted.

Buttons
=======

B1 USER: the user button is connected to the I/O PC13 (pin 2) of the STM32
microcontroller.

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

USART1
------
Pins and Connectors:

RXD: PA10 D3 CN9 pin 3, CN10 pin 33
PB7 CN7 pin 21
TXD: PA9 D8 CN5 pin 1, CN10 pin 21
PB6 D10 CN5 pin 3, CN10 pin 17

NOTE: You may need to edit the include/board.h to select different USART1
pin selections.

TTL to RS-232 converter connection:

Nucleo CN10 STM32F072RB
----------- ------------
Pin 21 PA9 USART1_TX *Warning you make need to reverse RX/TX on
Pin 33 PA10 USART1_RX some RS-232 converters
Pin 20 GND
Pin 8 U5V

To configure USART1 as the console:

CONFIG_STM32_USART1=y
CONFIG_USART1_SERIALDRIVER=y
CONFIG_USART1_SERIAL_CONSOLE=y
CONFIG_USART1_RXBUFSIZE=256
CONFIG_USART1_TXBUFSIZE=256
CONFIG_USART1_BAUD=115200
CONFIG_USART1_BITS=8
CONFIG_USART1_PARITY=0
CONFIG_USART1_2STOP=0

USART2
------
Pins and Connectors:

RXD: PA3 To be provided
PA15
PD6
TXD: PA2
PA14
PD5

See "Virtual COM Port" and "RS-232 Shield" below.

USART3
------
Pins and Connectors:

RXD: PB11 To be provided
PC5
PC11
D9
TXD: PB10
PC4
PC10
D8

USART3
------
Pins and Connectors:

RXD: PA1 To be provided
PC11
TXD: PA0
PC10

Virtual COM Port
----------------
Yet another option is to use UART2 and the USB virtual COM port. This
option may be more convenient for long term development, but is painful
to use during board bring-up.

Solder Bridges. This configuration requires:

- SB62 and SB63 Open: PA2 and PA3 on STM32 MCU are disconnected to D1
and D0 (pin 7 and pin 8) on Arduino connector CN9 and ST Morpho
connector CN10.

- SB13 and SB14 Closed: PA2 and PA3 on STM32F103C8T6 (ST-LINK MCU) are
connected to PA3 and PA2 on STM32 MCU to have USART communication
between them. Thus SB61, SB62 and SB63 should be OFF.

Configuring USART2 is the same as given above.

115200 8N1 BAUD should be configure to interface with the Virtual COM
port.

Default
-------
As shipped, SB62 and SB63 are open and SB13 and SB14 closed, so the
virtual COM port is enabled.

RS-232 Shield
-------------
Supports a single RS-232 connected via

Nucleo STM32F4x1RE Shield
--------- --------------- --------
CN9 Pin 1 PA3 USART2_RXD RXD
CN9 Pin 2 PA2 USART2_TXD TXD

Support for this shield is enabled by selecting USART2 and configuring
SB13, 14, 62, and 63 as described above under "Virtual COM Port"

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

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

cd tools
./configure.sh nucleo-l452re/
cd -

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 oldconfig
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 USART2, as described above under "Serial Console". The
elevant configuration settings are listed below:

CONFIG_STM32_USART2=y
CONFIG_STM32_USART2_SERIALDRIVER=y
CONFIG_STM32_USART=y

CONFIG_USART2_SERIALDRIVER=y
CONFIG_USART2_SERIAL_CONSOLE=y

CONFIG_USART2_RXBUFSIZE=256
CONFIG_USART2_TXBUFSIZE=256
CONFIG_USART2_BAUD=115200
CONFIG_USART2_BITS=8
CONFIG_USART2_PARITY=0
CONFIG_USART2_2STOP=0

3. All of these configurations are set up to build under Linux using the
"GNU Tools for ARM Embedded Processors" that is maintained by ARM
(unless stated otherwise in the description of the configuration).

https://developer.arm.com/open-source/gnu-toolchain/gnu-rm

That toolchain selection can easily be reconfigured using
'make menuconfig'. Here are the relevant current settings:

Build Setup:
CONFIG_HOST_LINUX=y : Linux environment

System Type -> Toolchain:
CONFIG_ARMV7M_TOOLCHAIN_GNU_EABIL=y : GNU ARM EABI toolchain

Configuration sub-directories
-----------------------------

nsh:

Configures the NuttShell (nsh) located at examples/nsh. This
configuration is focused on low level, command-line driver testing.