Memos that how to porting nuttx on microbit
https://tech.microbit.org/hardware/
https://en.wikipedia.org/wiki/ARM_Cortex-M#Cortex-M0
https://community.cypress.com/docs/DOC-10652
https://github.com/apache/incubator-nuttx https://github.com/apache/incubator-nuttx-apps
https://github.com/apache/incubator-nuttx/blob/nuttx-8.2/Documentation/NuttxPortingGuide.html
2.5.4 Adding a New Board Configuration
Okay, so you have created a new board configuration directory. Now, how do you hook this board into the configuration system so that you can select with make menuconfig?
You will need modify the file boards/Kconfig. Let's look at the STM32F4-Discovery configuration in the Kconfig file and see how we would add a new board directory to the configuration. For this configuration let's say that you new board resides in the directory boards/myarch/mychip/myboard; It uses an MCU selected with CONFIG_ARCH_CHIP_MYMCU; and you want the board to be selected with CONFIG_ARCH_BOARD_MYBOARD. Then here is how you can clone the STM32F4-Discovery configuration in boards/Kconfig to support your new board configuration.
https://tech.microbit.org/hardware/#interface
item details
Model Freescale MKL26Z128VFM4
Core variant: ARM Cortex-M0+
Flash ROM 128KB
RAM 16KB
Speed 16MHz
Debug capabilities SWD
https://www.nxp.com/part/MKL26Z128VFM4#/
https://github.com/apache/incubator-nuttx/blob/nuttx-8.2/boards/arm/kl/freedom-kl25z/README.txt#L100
Serial Console
==============
As with most NuttX configurations, the Freedom KL25Z configurations
depend on having a serial console to interact with the software. The
Freedom KL25Z, however, has no on-board RS-232 drivers so will be
necessary to connect the Freedom KL25Z UART pins to an external
RS-232 driver board or TTL-to-Serial USB adaptor.
By default UART0 is used as the serial console on this boards. The UART0
is configured to work with the OpenSDA USB CDC/ACM port:
------ ------------------------------- -----------------------------
PIN PIN FUNCTIONS BOARD SIGNALS
------ ------------------------------- -----------------------------
Pin 27 PTA1/TSI0_CH2/UART0_RX/FTM2_CH0 UART1_RX_TGTMCU and D0 (PTA1)
Pin 28 PTA2/TSI0_CH3/UART0_TX/FTM2_CH1 UART1_TX_TGTMCU and D1 (PTA2)
But the UART0 Tx/Rx signals are also available on J1:
---------------- ---------
UART0 SIGNAL J1 pin
---------------- ---------
UART0_RX (PTA1) J1, pin 2
UART0_TX (PTA2) J1, pin 4
Ground is available on J2 pin 14. 3.3V is available on J3 and J4.
https://acassis.wordpress.com/2013/04/02/compiling-nuttx-for-cortex-m0/ https://github.com/apache/incubator-nuttx/tree/master/boards/arm/nuc1xx/nutiny-nuc120
https://github.com/dwelch67/microbit
http://bluetooth.tokyo/wp-content/uploads/2018/03/nRF51-VS-nRF52.jpg
