2019-09-22 18:43:36 +02:00
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README
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======
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This README discusses issues unique to NuttX configurations for the
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Arduino M0. I used a compatible board called Wemos SAMD21 M0 board,
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but there are other equivalent boards, like the RobotDyn SAMD21 M0.
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Unfortunately because the Arduino.cc vs Arduino.org conflict in the past,
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we have three types of boards: Arduino Zero, Arduino M0 and Arduino M0 Pro.
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The Wemos SAMD21 M0 is compatible with Arduino M0, but not exactly a clone.
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You have two options to program it: using the SWD (EDBG) connector that
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comes in the board or the Arduino M0 bootloader that comes flashed on it.
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Currently only SWD programming is supported. Bootloader skip area should be
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implemented to avoid overwriting the bootloader area.
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The board uses the ATSAMD21G18A MCU and can work over the Native USB Port.
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Contents
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========
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- STATUS/ISSUES
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- LEDs
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- Serial Consoles
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- Configurations
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STATUS/ISSUES
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=============
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Because the Arduino M0 doesn't have a 12MHz crystal, it uses the internal
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RC oscillator.
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LEDs
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====
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There is one yellow LED available on the Arduino M0 and it can be turned
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on and off. The LED can be activated by driving the connected
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PA17 I/O line to high level.
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When CONFIG_ARCH_LEDS is defined in the NuttX configuration, NuttX will
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control the LED as follows:
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SYMBOL Meaning LED0
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------------------- ----------------------- ------
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LED_STARTED NuttX has been started OFF
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LED_HEAPALLOCATE Heap has been allocated OFF
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LED_IRQSENABLED Interrupts enabled OFF
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LED_STACKCREATED Idle stack created ON
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LED_INIRQ In an interrupt N/C
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LED_SIGNAL In a signal handler N/C
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LED_ASSERTION An assertion failed N/C
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LED_PANIC The system has crashed FLASH
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Thus is LED is statically on, NuttX has successfully booted and is,
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apparently, running normally. If LED is flashing at approximately
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2Hz, then a fatal error has been detected and the system has halted.
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Serial Consoles
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===============
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SERCOM5
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------
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SERCOM5 is available on pins PB22 (TXD) and PB23 (RXD). You will need to
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solder a two pins header to RXD and TXD labels, near to ICSP pin header.
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PIN GPIO Function
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---- ---- ------------------
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37 PB22 SERCOM5 / USART RX
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38 PB23 SERCOM5 / USART TX
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If you have a 3.3V USB/Serial adapter then this is the most convenient
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serial console to use (because you don't lose the console device each time
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you lose the USB connection). It is the default in all of these
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configurations. An option is to use the virtual COM port.
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Native USB Port
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---------------
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You can access the NSH shell directly using the USB connector. All you need
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to do is use the "usbnsh" board profile.
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Configurations
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==============
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Each Arduino M0 configuration is maintained in a sub-directory and
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can be selected as follow:
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tools/configure.sh arduino-m0:<subdir>
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Before building, make sure the PATH environment variable include the
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correct path to the directory than holds your toolchain binaries.
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And then build NuttX by simply typing the following. At the conclusion of
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the make, the nuttx binary will reside in an ELF file called, simply, nuttx.
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make
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The <subdir> that is provided above as an argument to the tools/configure.sh
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must be is one of the following.
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NOTE: These configurations use the mconf-based configuration tool. To
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change any of these configurations using that tool, you should:
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a. Build and install the kconfig-mconf tool. See nuttx/README.txt
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see additional README.txt files in the NuttX tools repository.
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b. Execute 'make menuconfig' in nuttx/ in order to start the
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reconfiguration process.
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NOTES:
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1. These configurations use the mconf-based configuration tool. To
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change any of these configurations using that tool, you should:
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a. Build and install the kconfig-mconf tool. See nuttx/README.txt
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see additional README.txt files in the NuttX tools repository.
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b. Execute 'make menuconfig' in nuttx/ in order to start the
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reconfiguration process.
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Configuration sub-directories
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-----------------------------
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nsh:
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This configuration directory will built the NuttShell. See NOTES above
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and below:
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NOTES:
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1. This configuration is set up to build on Windows using the Cygwin
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environment using the CodeSourcery toolchain. This can be easily
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changed as described above under "Configurations."
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2. By default, this configuration provides a serial console on SERCOM5
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at 115200 8N1 via RXD/TXD pads:
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PIN EXT3 GPIO Function
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---- ---- ------------------
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37 PB22 SERCOM5 / USART RX
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38 PB23 SERCOM5 / USART TX
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2019-09-23 00:13:06 +02:00
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usbnsh:
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This configuration directory will build the NuttShell to work over USB.
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It uses the internal SAMD21 USB port working as CDC/ACM Serial/Modem.
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Using the configuration you don't need to solder the header pins RXD/TXD
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to get access the NSH terminal.
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