esp32: add espnow documentation and defconfig.

Added documentation for espnow and a default defconfig to illustrate
the use of espnow for udp communication.

Signed-off-by: Laczen JMS <laczenjms@gmail.com>

Documentation/platforms/xtensa/esp32/boards/esp32-devkitc/index.rst

@@ -305,10 +305,10 @@ the following output is expected::
     nsh> cap
     cap_main: Hardware initialized. Opening the capture device: /dev/capture0
     cap_main: Number of samples: 0
-    pwm duty cycle: 50 % 
+    pwm duty cycle: 50 %
-    pwm frequence: 50 Hz 
+    pwm frequence: 50 Hz
-    pwm duty cycle: 50 % 
+    pwm duty cycle: 50 %
-    pwm frequence: 50 Hz 
+    pwm frequence: 50 Hz
 
 coremark
 --------
@@ -384,6 +384,30 @@ elf
 This configuration uses apps/examples/elf in order to test the ELF loader.
 It can be tested by executing the ``elf`` application.
 
+espnow
+------
+
+A ``espnow`` setup can be used to create a 6lowpan network of esp32 nodes.
+A sample configuration is found in ``esp32-devkitc:espnow``. The node
+address can be changed under ``ESP32 Peripherals`` option ``Espnow``. To
+test the communication using ``udpserver`` and ``udpclient`` two nodes
+need to be prepared using e.g. node address ``0x0a`` and ``0x0b``.
+
+On node ``0x0a`` the server can be started using:
+
+``nsh> ifup wpan0``
+``ifup wpan0..OK``
+``nsh> udpserver &``
+
+On node ``0x0b`` the client can be started using:
+
+``nsh> ifup wpan0``
+``ifup wpan0..OK``
+``nsh> udpclient fe80::ff:fe00:a``
+
+The client node will show that the messages are sent while the server
+shows that messages are received.
+
 i2schar
 -------
 
@@ -1088,7 +1112,7 @@ you can confirm it is working this way::
             RX errors 0  dropped 0  overruns 0  frame 0
             TX packets 5666  bytes 547514 (547.5 KB)
             TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
-    
+
     wlp0s20f3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
             inet 10.0.0.4  netmask 255.255.255.0  broadcast 10.0.0.255
             inet6 xxxx::xxxx:xxx:xxxx:xx  prefixlen 64  scopeid 0x20<link>
@@ -1097,7 +1121,7 @@ you can confirm it is working this way::
             RX errors 0  dropped 0  overruns 0  frame 0
             TX packets 37079  bytes 23604536 (23.6 MB)
             TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
-    
+
     $ ping 10.0.0.1
     PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data.
     64 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=3.28 ms
@@ -1105,7 +1129,7 @@ you can confirm it is working this way::
     64 bytes from 10.0.0.1: icmp_seq=3 ttl=64 time=2.63 ms
     64 bytes from 10.0.0.1: icmp_seq=4 ttl=64 time=18.9 ms
     64 bytes from 10.0.0.1: icmp_seq=5 ttl=64 time=4.82 ms
-    
+
     $ ping 8.8.8.8
     PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
     64 bytes from 8.8.8.8: icmp_seq=1 ttl=111 time=63.0 ms

boards/xtensa/esp32/esp32-devkitc/configs/espnow/defconfig

@@ -0,0 +1,98 @@
+#
+# This file is autogenerated: PLEASE DO NOT EDIT IT.
+#
+# You can use "make menuconfig" to make any modifications to the installed .config file.
+# You can then do "make savedefconfig" to generate a new defconfig file that includes your
+# modifications.
+#
+# CONFIG_ARCH_LEDS is not set
+# CONFIG_NDEBUG is not set
+# CONFIG_NET_UDP_CHECKSUMS is not set
+# CONFIG_NSH_ARGCAT is not set
+# CONFIG_NSH_CMDOPT_HEXDUMP is not set
+CONFIG_ALLOW_BSD_COMPONENTS=y
+CONFIG_ARCH="xtensa"
+CONFIG_ARCH_BOARD="esp32-devkitc"
+CONFIG_ARCH_BOARD_COMMON=y
+CONFIG_ARCH_BOARD_ESP32_DEVKITC=y
+CONFIG_ARCH_CHIP="esp32"
+CONFIG_ARCH_CHIP_ESP32=y
+CONFIG_ARCH_CHIP_ESP32WROVER=y
+CONFIG_ARCH_INTERRUPTSTACK=2048
+CONFIG_ARCH_STACKDUMP=y
+CONFIG_ARCH_XTENSA=y
+CONFIG_BOARD_LOOPSPERMSEC=16717
+CONFIG_BUILTIN=y
+CONFIG_DEFAULT_TASK_STACKSIZE=4096
+CONFIG_DEV_URANDOM=y
+CONFIG_DRIVERS_IEEE80211=y
+CONFIG_DRIVERS_WIRELESS=y
+CONFIG_ESP32_ESPNOW_PKTRADIO=y
+CONFIG_ESP32_ESPNOW_PKTRADIO_NODE_ADDR_0=0x0a
+CONFIG_ESP32_SPIFLASH=y
+CONFIG_ESP32_SPIFLASH_SPIFFS=y
+CONFIG_ESP32_STORAGE_MTD_SIZE=0x80000
+CONFIG_ESP32_UART0=y
+CONFIG_ESP32_WIFI=y
+CONFIG_EXAMPLES_UDP=y
+CONFIG_EXAMPLES_UDP_DEVNAME="wpan0"
+CONFIG_EXAMPLES_UDP_IPv6=y
+CONFIG_EXAMPLES_UDP_SERVER1=y
+CONFIG_EXAMPLES_UDP_TARGET2=y
+CONFIG_FS_PROCFS=y
+CONFIG_IDLETHREAD_STACKSIZE=3072
+CONFIG_INIT_ENTRYPOINT="nsh_main"
+CONFIG_INIT_STACKSIZE=3072
+CONFIG_INTELHEX_BINARY=y
+CONFIG_LINE_MAX=300
+CONFIG_MM_REGIONS=3
+CONFIG_NAME_MAX=48
+CONFIG_NETDB_DNSCLIENT=y
+CONFIG_NETDB_DNSCLIENT_NAMESIZE=64
+CONFIG_NETDEV_LATEINIT=y
+CONFIG_NETDEV_PHY_IOCTL=y
+CONFIG_NETDEV_TELNET=y
+CONFIG_NETDEV_WIRELESS_IOCTL=y
+CONFIG_NETUTILS_CJSON=y
+CONFIG_NET_6LOWPAN=y
+CONFIG_NET_BROADCAST=y
+CONFIG_NET_ETH_PKTSIZE=1518
+CONFIG_NET_ICMP_SOCKET=y
+CONFIG_NET_IPv6=y
+CONFIG_NET_PREALLOC_DEVIF_CALLBACKS=32
+CONFIG_NET_STATISTICS=y
+CONFIG_NET_TCP=y
+CONFIG_NET_TCP_DELAYED_ACK=y
+CONFIG_NET_TCP_WRITE_BUFFERS=y
+CONFIG_NET_UDP=y
+CONFIG_NSH_ARCHINIT=y
+CONFIG_NSH_BUILTIN_APPS=y
+CONFIG_NSH_FILEIOSIZE=512
+CONFIG_NSH_READLINE=y
+CONFIG_POSIX_SPAWN_DEFAULT_STACKSIZE=2048
+CONFIG_PREALLOC_TIMERS=4
+CONFIG_PTHREAD_MUTEX_TYPES=y
+CONFIG_RAM_SIZE=114688
+CONFIG_RAM_START=0x20000000
+CONFIG_READLINE_CMD_HISTORY=y
+CONFIG_RR_INTERVAL=200
+CONFIG_SCHED_LPWORK=y
+CONFIG_SCHED_WAITPID=y
+CONFIG_SIG_DEFAULT=y
+CONFIG_SPI=y
+CONFIG_SPIFFS_NAME_MAX=48
+CONFIG_START_DAY=6
+CONFIG_START_MONTH=12
+CONFIG_START_YEAR=2011
+CONFIG_SYSLOG_BUFFER=y
+CONFIG_SYSLOG_CONSOLE=y
+CONFIG_SYSTEM_ARGTABLE3=y
+CONFIG_SYSTEM_DHCPC_RENEW=y
+CONFIG_SYSTEM_NSH=y
+CONFIG_TLS_TASK_NELEM=4
+CONFIG_UART0_SERIAL_CONSOLE=y
+CONFIG_WIRELESS=y
+CONFIG_WIRELESS_PKTRADIO=y
+CONFIG_WIRELESS_WAPI=y
+CONFIG_WIRELESS_WAPI_CMDTOOL=y
+CONFIG_WIRELESS_WAPI_INITCONF=y