Day: January 4, 2018

Running NuttX on ESP32 board

NuttX supports the Expressif ESP32 inclusive with SMP (Symmetric MultiProcessing) support, then I decided to post here the steps I followed to get it working:

Install esptool:

$ sudo pip install esptool

Install to toolchain:

You can download the pre-build toolchain:

Or: you can compile it from source code:

$ git clone -b xtensa-1.22.x
$ cd crosstool-NG
$ ./bootstrap && ./configure --prefix=$PWD && make install
$ ./ct-ng xtensa-esp32-elf
$ ./ct-ng build
$ chmod -R u+w builds/xtensa-esp32-elf
$ sudo cp -a builds/xtensa-esp32-elf/* /usr/local/

Now you can compile the NuttX:

$ mkdir ~/nuttxspace
$ cd ~/nuttxspace
$ git clone
$ git clone
$ cd nuttx
$ make distclean
$ ./tools/ esp32-core/nsh
$ make

The nuttx.bin generated is too big, you need to generate it from elf file (nuttx) :

$ --chip esp32 elf2image --flash_mode dio --flash_size 4MB -o ./nuttx.bin nuttx

You will need the bootloader.bin and the partitions, you can get it from hello word example. You need to clone and update the submodules of esp-idf (read the Get Started from above link), then:

$ cp -a esp-idf/examples/get-started/hello_world .
$ cd hello_world
$ make
$ cp build/bootloader/bootloader.bin ~/nuttxspace/nuttx/
$ cp build/partitions_singleapp.bin ~/nuttxspace/nuttx/partitions.bin

The files nuttx.bin, bootloader.bin and partitions.bin need to be flashed in the board. To do that first put the board in ROM Boot mode:

Press and hold the BOOT button of ESP32 board (IO0 pin will be put in low level) and press and release the RESET button. Now you can release the BOOT button.

This is the command to flash:

$ sudo --chip esp32 --port /dev/ttyUSB0 --baud 921600 write_flash 0x1000 bootloader.bin 0x8000 partitions.bin 0x10000 nuttx.bin v2.2
Chip is ESP32D0WDQ6 (revision 0)
Uploading stub...
Running stub...
Stub running...
Changing baud rate to 921600
Configuring flash size...
Auto-detected Flash size: 4MB
Flash params set to 0x0220
Compressed 19392 bytes to 11445...
Wrote 19392 bytes (11445 compressed) at 0x00001000 in 0.2 seconds (effective 901.6 kbit/s)...
Hash of data verified.
Compressed 3072 bytes to 82...
Wrote 3072 bytes (82 compressed) at 0x00008000 in 0.0 seconds (effective 10507.6 kbit/s)...
Hash of data verified.
Compressed 185024 bytes to 45527...
Wrote 185024 bytes (45527 compressed) at 0x00010000 in 2.1 seconds (effective 710.2 kbit/s)...
Hash of data verified.

Hard resetting...

Finally open minicom and just reset the board, you should get it:

$ minicom

Welcome to minicom 2.7

Compiled on Feb  7 2016, 13:37:27.
Port /dev/ttyUSB0, 15:40:48

Press CTRL-A Z for help on special keys

ets Jun  8 2016 00:22:57

ets Jun  8 2016 00:22:57

configsip: 0, SPIWP:0xee
mode:DIO, clock div:2
ho 0 tail 12 room 4
entry 0x40078fb4
I (31) boot: ESP-IDF v3.1-dev-162-geb659e4 2nd stage bootloader
I (31) boot: compile time 15:35:11
I (42) boot: Enabling RNG early entropy source...
I (42) boot: SPI Speed      : 40MHz
I (42) boot: SPI Mode       : DIO
I (45) boot: SPI Flash Size : 4MB
I (49) boot: Partition Table:
I (52) boot: ## Label            Usage          Type ST Offset   Length
I (60) boot:  0 nvs              WiFi data        01 02 00009000 00006000
I (67) boot:  1 phy_init         RF data          01 01 0000f000 00001000
I (75) boot:  2 factory          factory app      00 00 00010000 00100000
I (82) boot: End of partition table
I (86) esp_image: segment 0: paddr=0x00010020 vaddr=0x3ffb0df0 size=0x00054 (    84) load
I (95) esp_image: segment 1: paddr=0x0001007c vaddr=0x40080000 size=0x00400 (  1024) load
I (104) esp_image: segment 2: paddr=0x00010484 vaddr=0x40080400 size=0x00300 (   768) load
I (113) esp_image: segment 3: paddr=0x0001078c vaddr=0x400c0000 size=0x00000 (     0) load
I (122) esp_image: segment 4: paddr=0x00010794 vaddr=0x00000000 size=0x0f874 ( 63604) 
I (153) esp_image: segment 5: paddr=0x00020010 vaddr=0x3f400010 size=0x018e4 (  6372) map
I (155) esp_image: segment 6: paddr=0x000218fc vaddr=0x00000000 size=0x0e714 ( 59156) 
I (179) esp_image: segment 7: paddr=0x00030018 vaddr=0x400d0018 size=0x0d278 ( 53880) map
I (199) boot: Loaded app from partition at offset 0x10000
I (199) boot: Disabling RNG early entropy source...

NuttShell (NSH)
nsh> ?
help usage:  help [-v] []

  [           cmp         false       mkdir       rm          true        
  ?           dirname     free        mh          rmdir       uname       
  basename    dd          help        mount       set         umount      
  break       df          hexdump     mv          sh          unset       
  cat         echo        kill        mw          sleep       usleep      
  cd          exec        ls          ps          test        xd          
  cp          exit        mb          pwd         time        

Builtin Apps:

P.S.: If your board is rebooting, then disable the RTC watchdog in the bootloader.