ESP-NOW to WiFi border router for RIOT-OS

Overview

This application realizes a border router for RIOT-OS using the GNRC stack which connects an ESP-NOW based mesh network to an infrastructure mode WiFi network using an ESP32 or an ESP8266. It can be used to extend a network of ESP32 and ESP8266 nodes where not all nodes are able to connect to an AP of the infrastructure mode WiFi network.

The border router uses the modules esp_now and esp_wifi

• to create two GNRC network interfaces (the inner interface using ESP-NOW and the outer interface using WiFi) and
• to route packets between the ESP-NOW based mesh networks and the infrastructure mode WiFi network.

Please note

• Since the WiFi interface of ESP nodes can only operate on one channel at a time, the ESP-NOW based mesh network has to use the same channel as it is used by the AP of the infrastructure-mode WiFi network. For that purpose the border router and all ESP-NOW nodes have to be compiled using configuration parameter ESP_NOW_CHANNEL.

• Although an ESP8266 could also be used as a border router, it is strongly recommended to use an ESP32 because of the very small RAM of the ESP8266. Because ESP-NOW is compatible on ESP832 and ESP8266 nodes, the ESP-NOW based mesh network can be any mix of ESP32 and ESP8266 nodes.

How to compile

Clone the border router repository.

git clone https://github.com/gschorcht/RIOT_ESP_NOW_WiFi_Border_Router.git

Change to the directory.

cd RIOT_ESP_NOW_WiFi_Border_Router

Set variable RIOTBASE to your RIOT-OS directory.

export RIOTBASE=<RIOT-OS directory>

Compile an flash the border router using the following command

CFLAGS='-DESP_NOW_CHANNEL=<channel> -DESP_WIFI_SSID=\"<SSID>\" -DESP_WIFI_PASS=\"<passphrase>\"' \
make BOARD=... PORT=/dev/... flash

<channel> specifies the channel, <SSID> the SSID and <passphrase> the PSK as used by the AP of your infrastructure mode WiFi network. Declare variables BOARD and PORT according to your configuration. If BOARD is omitted, esp32-wroom-32 is used as default.

If you would like to use RPL for routing in the ESP-NOW based mesh network, just add module gnrc_rpl as following.

USEMODULE=gnrc_rpl \
CFLAGS='-DESP_NOW_CHANNEL=<channel> -DESP_WIFI_SSID=\"<SSID>\" -DESP_WIFI_PASS=\"<passphrase>\"' \
make BOARD=... PORT=/dev/... flash

Compile and flash all ESP-NOW nodes with same <channel> as the border router.

cd $RIOTBASE
USEMODULE='esp_now' CFLAGS='-DESP_NOW_CHANNEL=<channel>' \
make -C examples/gnrc_networking BOARD=... PORT=/dev/... flash

How to use

Once the border router and all ESP-NOW nodes are flashed, a terminal program can be used to connect to the border router and the nodes, for example with:

python -m serial.tools.miniterm /dev/... 115200

Within the terminal, different shell commands like ifconfig, ping6 or rpl can be used to get information about the status of the nodes. By typing help you will get the list of available shell commands.

Border router

On the border router, the ps command should show the following two processes

	pid | name                 | state    Q | pri | stack  ( used) | base addr  | current
          ...
	  7 | esp-now              | bl rx    _ |  10 |   2048 (  960) | 0x3ffb64d0 | 0x3ffb6ab0 
	  8 | esp-wifi             | bl rx    _ |   9 |   2048 (  892) | 0x3ffb6e1c | 0x3ffb73f0 

and the ifconfig command should give two interfaces, for example,

Iface  7  HWaddr: 30:AE:A4:18:7A:3D 
          MTU:1280  HL:64  RTR  
          RTR_ADV  6LO  Source address length: 6
          Link type: wireless
          inet6 addr: fe80::32ae:a4ff:fe18:7a3d  scope: local  VAL
          inet6 addr: 2001:db8::32ae:a4ff:fe18:7a3d  scope: global  VAL
          inet6 group: ff02::2
          inet6 group: ff02::1
          inet6 group: ff02::1:ff18:7a3d
          inet6 group: ff02::1a
          
Iface  8  HWaddr: 30:AE:A4:18:7A:3C  Link: up 
          MTU:1440  HL:255  RTR  
          Source address length: 6
          Link type: wireless
          inet6 addr: fe80::32ae:a4ff:fe18:7a3c  scope: local  VAL
          inet6 addr: 2003:c1:e715:fc23:32ae:a4ff:fe18:7a3c  scope: global  VAL
          inet6 group: ff02::2
          inet6 group: ff02::1
          inet6 group: ff02::1:ff18:7a3c

where interface 7 is the ESP-NOW interface and interface 8 the WiFi interface. The ESP-NOW interface should already have a global unicast address with prefix 2001:db8::/64. The WiFi interface only gets a global unicast address if the router in your LAN provides a global routing prefix.

If you have enabled RPL by module gnrc_rpl, it should have been initialized and command rpl should result into something like the following.

instance table:	[X]	
parent table:	[ ]	[ ]	[ ]	

instance [0 | Iface: 7 | mop: 2 | ocp: 0 | mhri: 256 | mri 0]
	dodag [2001:db8::32ae:a4ff:fe18:7a3d | R: 256 | OP: Router | PIO: on | TR(I=[8,20], k=10, c=1, TC=2s)]

ESP-NOW nodes

On ESP-NOW nodes, you sould only see one process like

	pid | name                 | state    Q | pri | stack  ( used) | base addr  | current     
	  ...
	  8 | esp-now              | bl rx    _ |  10 |   2560 (  736) | 0x3fff4340 | 0x3fff4be0 

and the ifconfig command should give one interface, for example:

Iface  8  HWaddr: 62:01:94:82:7A:1D 
          MTU:1280  HL:64  RTR  
          RTR_ADV  6LO  Source address length: 6
          Link type: wireless
          inet6 addr: fe80::6001:94ff:fe82:7a1d  scope: local  VAL
          inet6 addr: 2001:db8::6001:94ff:fe82:7a1d  scope: global  VAL
          inet6 group: ff02::2
          inet6 group: ff02::1
          inet6 group: ff02::1:ff82:7a1d
          inet6 group: ff02::1a

The ESP-NOW interface should already have a global unicast address with prefix 2001:db8::/64.

If RPL was enabled on border router, command rpl should result into something like the following after some seconds.

instance [0 | Iface: 8 | mop: 2 | ocp: 0 | mhri: 256 | mri 0]
	dodag [2001:db8::32ae:a4ff:fe18:7a3d | R: 512 | OP: Router | PIO: on | TR(I=[8,20], k=10, c=0, TC=8s)]
		parent [addr: fe80::32ae:a4ff:fe18:7a3d | rank: 256]

You should be able to ping the border router and other ESP-NOW nodes using their IPv6 global unicast address with prefix 2001:db8::/64, for example:

ping6 2001:db8::5ccf:7fff:fe94:76a9

Furthermore, if you configure a route to 2001:db8::/64 on your machine in the LAN using the link local unicast address of the WiFi interface of the border router, for example,

sudo ip -6 route add 2001:db8::/64 via fe80::32ae:a4ff:fe18:7a3c dev eth0

you should be able to ping the ESP-NOW nodes from your machine and vise versa.

ping6 2001:db8::6001:94ff:fe82:7a1d

That is, ESP-NOW nodes are then able now to communicate with arbitrary networks via the border router provided that packets with prefix 2001:db8::/64 are routed to the WiFi interface of your border router.