Libraries
Library espnow
To use this library in your code:
import esp32.espnowESP-NOW communication for ESP32 devices.
ESP-NOW is a proprietary protocol developed by Espressif for low-power, connection-less communication between ESP32 devices.
Devices can either communicate by broadcasting messages to all devices in range, or by sending messages to specific devices using their MAC address. In both cases, a key can be used to encrypt the messages.
Limitations
Messages are at most 1470 bytes long. For broadcast messages there is no guarantee that messages are correctly delivered. For direct messages, the implementation ensures that the PHY layer has received the message, but there is no guarantee that the message is processed by the receiving device.
ESP-NOW only supports 20 peers, although one peer-slot can be used to communicate with all devices in range by specifying the broadcast address.
By default only 7 keys can be used. This can be changed in the sdkconfig, but that requires building a custom envelope.
In theory, ESP-NOW can run at the same times as Wifi, but this library currently does not support this.
Examples
Broadcasting an unencrypted message:
service := espnow.Service
service.add-peer espnow.BROADCAST-ADDRESS
service.send "hello world"
--address=espnow.BROADCAST-ADDRESS
service.close
Receiving a message:
service := espnow.Service
message := service.receive // Blocks until a message is received.
sender := message.address
data := message.data.to-string
print "Received datagram from $sender: $data"
service.close
Sending to a peer with encryption:
// On both sides, create a key for the peer.
key := espnow.Key.from-string "0123456789abcdef"
// The address of the receiver.
peer := espnow.Address.parse "aa:bb:cc:dd:ee:ff"
service := espnow.Service
service.add-peer peer --key=key
service.send "hello world" --address=peer
service.close
Receiving from a peer with encryption:
key := espnow.Key.from-string "0123456789abcdef"
// The address of the sender.
peer := espnow.Address.parse "ff:ee:dd:cc:bb:aa"
service := espnow.Service
service.add-peer peer --key=key
message := service.receive // Blocks until a message is received.
sender := message.address
data := message.data.to-string
print "Received datagram from $sender: $data"
service.close
Globals
PHY mode for 11a.
PHY mode for 11b.
PHY mode for 11g.
PHY mode for HE20.
PHY mode for HT20.
PHY mode for HT40.
PHY mode for Low Rate (LR)
PHY mode for VHT20.
11 Mbps with long preamble.
11 Mbps with short preamble.
12 Mbps.
18 Mbps.
1 Mbps with long preamble.
24 Mbps.
2 Mbps with long preamble.
2 Mbps with short preamble.
36 Mbps.
48 Mbps.
54 Mbps.
5.5 Mbps with long preamble.
5.5 Mbps with short preamble.
6 Mbps.
9 Mbps.
MCS8 with long GI.
This rate might not be supported by all devices.
MCS8 with short GI.
This rate might not be supported by all devices.
MCS9 with long GI.
This rate might not be supported by all devices.
MCS9 with short GI.
This rate might not be supported by all devices.