ESP-NOW: Difference between revisions
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ESP-NOW is | ESP-NOW is intended as for ESP-to-ESP communication, based on WiFi but not requiring association. | ||
It lets ESP devices send (small, unACKed) packets to other ESP devices | |||
: directly (without an AP) | |||
: coexisting with the regular WiFi stack (but there are practical footnotes) | |||
Some explanations mention that you pair with a peer, | |||
and will automatically recover after restart. | |||
...which seems to be a fancy way of saying that it's stateless, | |||
that you need to send to a specific MAC, | |||
...which seems to be a | that you have to know and will probably either hardcode or somehow discover" | ||
There is also a note that you can actually use broadcasts, in which case you don't have a peer limit. | There is also a note that you can actually use broadcasts, in which case you don't have a peer limit. | ||
Limitations: | Limitations: | ||
* it will use the same channel as WiFi | |||
:: so if you switch to a specific AP, ESP-now will _follow_ that, which probably not what you want | |||
- | |||
* Fire-and-forget - No ACKs | |||
* 250 bytes of payload, because it uses Action Frames | |||
* can't receive if in modem sleep | |||
** note: it can make sense to have one ESP stay awake and have others poll it between sleep, though at this point it's not too differrent from that being a real AP - in fact might you get TIM on a real AP) | |||
** there are some other things in STA mode, see e.g. esp_now_set_wake_window() | |||
* different peer limits exist in Station mode and in AP mode or AP+Station mode | |||
* Assume the sending rate is no faster than 1Mbps ''at best'' but usually slower. | |||
* you will receive whatever is sent to you. | |||
** You need to figure out that message is for your type of device, | |||
** and/or whether it is a type of message you want to respond to | |||
* no encryption in a practical sense | |||
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Revision as of 14:38, 22 June 2024