README

This is the README file for the port of NuttX to the Arduino Mega 2560 Rev3.

https://www.arduino.cc/en/Main/ArduinoBoardMega2560

The board is based on ATMega2560 chip from Atmel

http://www.atmel.com/devices/atmega2560.aspx

Contents

o Toolchain o Serial Console o Configurations

Toolchain

Right now only Atmel's AVR8 Toolchain is supported. You can get it from

http://www.atmel.com/tools/atmelavrtoolchainforwindows.aspx

It is basically WinAVR compatible so sub-projects may define WinAVR as a tool-chain but specify path to the Atmel AVR8 in path. See arduino-mega2560/hello for example.

Serial Console

The serial console is available on USART0. You will need to connect an RS-232 shield or an external RS-232 driver as follows:

TXD: TX0->1
RXD: RX0->0
GND: Power GND
+5V: Power +5V

You will then need to use a terminal program configured at 38400 8N1.

Configurations

Common Configuration Notes

1. Each Arduino MEGA2560 configuration is maintained in a sub-directory and can be selected as follow:

   tools/configure.sh arduino-mega2560:<subdir>

 Where <subdir> is one of the configuration sub-directories described in
 the following paragraph.

2. These configurations use the mconf-based configuration tool. To change a 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.

3. By default, all configurations assume the Atmel Studio AVR8 toolchain under Cygwin with Windows. This is easily reconfigured:

   CONFIG_HOST_WINDOWS=y CONFIG_WINDOWS_CYGWIN=y CONFIG_AVR_BUILDROOT_TOOLCHAIN=y

Configuration Sub-Directories

hello: The simple apps/examples/hello "Hello, World!" example.

nsh: This is a reduce NuttShell (NSH) configuration using apps/example/nsh. The serial console is provided on USART0 and can be accessed via an external RS-232 driver as described above under "Serial Console".

NOTES:

1. As of 2015-01-16, the default static memory usage is:

     $ size nuttx.elf
      text    data     bss     dec     hex filename
     34348    2117     944   37409    9221 nuttx.elf

   And dynamic, heap usage:

     nsh> free
                  total       used       free    largest
     Mem:          4736       1768       2968       2968

   There is plenty of FLASH space but not a lot of free SRAM. This
   SRAM usage is due primarily to constant strings defined by NSH.

   NOTE: I investigated the possibility of adding IPTR/IOBJ
   qualifiers in the NSH library and moving the strings to FLASH.
   This is still a possibility but would requires some extensive
   changes to NSH.