Repeaters
A repeater would be a cheap ESP32 that hears the link and passes it on, so a boardShort for bulletin board, a BBS. On this site, one BBS and the community that meets on it. can reach a sat sitting further off than its own radio carries. Put up several and they would work out between themselves which of them talks to which.
None of this is built. There is no repeater code in the firmware, no version it is coming in and nothing to install. This page is the design, written down so it can be argued with. The roadmap has it under Later, with no date.
What works today
Everything below starts from the link a board and a sat already have. One board, one sat, both in radio range: they pair once, then talk straight from chip to chip over ESP-NOW, with nothing in between and nothing going through your router.
That is firmware 1.2.0, and a camera sat is the one you can build. What it cannot do is reach round a house or down to the end of a long garden, because 2.4 GHz does not bend.
Why you would want one
Because the interesting places to put a sat are the awkward ones. A camera watching the bird feeder at the bottom of the garden, a sensor in a barn, a switch in a workshop across the yard. The sat itself is small and draws almost nothing, so putting one there is easy; getting its radio back to the board is the hard part.
Today the answers are to move the board, move the sat, or run a wire. A repeater would be a third: a box in between that hears both ends.
The box needs no wire back to the board and no mains if you do not have any. A board draws under two watts even with a 4.3 inch screen running, and a repeater has no screen and no card, so it is a small solar panel and a battery. That is the whole reason this is worth designing: it puts the far end of your board's reach somewhere there is nothing at all.
How far would it reach?
Further than one radio, and nobody can tell you how much further.
Range at 2.4 GHz is decided by what is in the way and what antenna each end has, not by a number in a specification. A clear line of sight across a field is a different world from two brick walls and a fridge. Some ESP32 boards take an external antenna, which helps both directions at once, and the legal limit in your country is on radiated power rather than on distance.
So the honest answer is that a repeater buys you the hop you cannot make, and the only way to know how many you need is to put one up and look. Anything on this page that reads like a distance is a mistake; please tell us.
Several of them, and nobody plants the routes
Rob's own example, and the one this was asked for: a BBS at home, a few repeaters, and a camera sat somewhere out of the way taking pictures of wildlife.
You put the boxes up. Which one carries what is not your problem, and that is the part Rob chose: not a line of boxes with the route written down by hand, but a mesh that works itself out and puts itself back together when a piece of it stops answering.
Your board is the root of it. Each box tells the board what it can hear; the board, and only the board, holds the whole map; and the board works out the way to every sat. A frame going out carries the route the board picked, written into it, so each box along the way reads off who is next and forwards it. A frame coming in goes up from box to box until it reaches the board.
What the board never does is pass a frame between two boxes for its own sake. Every frame on the mesh is either on its way to your board or on its way out from it, which is what keeps other people's traffic off the chip your callers are using.
Nothing is ever shouted at everybody
Forwarding a frame is easy. Several boxes that each pass on everything they hear is not a network, it is a shouting match: the second repeats the first, the first repeats the second repeating it, and the air fills up with one picture going round in circles. This is the thing that actually goes wrong with a radio repeater, and it is worth knowing how the design avoids it.
It avoids it by never doing it. There is no frame a box ever passes on to everybody: on the way in, one box hands to one box, each hop a little closer to the board; on the way out, each box reads the next name off the route the board wrote and sends to that one and no other. Even a new sat asking to be let in is carried up by one box rather than shouted about. A frame that is going the wrong way is noticed and dropped, and one that has been handed on too many times is dropped too.
None of that is hard in the sense of being unsolved. It is the difference between a weekend and a month, and it is why this is a design on a page rather than a release with a number.
When one goes flat
A box on a pole runs out of sun, or somebody takes it, or it simply dies. Three things would happen, each slower and more thorough than the last, and none of them yours to do:
- the frame that finds the dead box goes to the next box that one knows about, there and then, without asking anybody
- the board hears that the way is broken and sends what follows round the other side, out of the map it already holds
- and then it works the whole map out again
What a camera behind it looks like is a gap in the pictures. What a sysop sees is which box stopped answering, and a way to tell the board to forget it for good.
There is one case a mesh does not help with, and it is the same one a single sat already has: if your router changes channel, your board follows it and every box is left behind on the old one. They find it again, the near ones first and the far ones after, and nobody has measured how long that takes, so there is no figure for it here.
Everything is on one channel
This is the part people get wrong about repeaters, so it is worth being plain. An ESP32 has one radio and sits on one Wi-Fi channel at a time. Your board's channel is whichever one your router is using, and every sat follows it. A repeater has one radio too, so every one of its hops is on that same channel.
Which means a hop does not add capacity, it spends it. The same picture goes over the air once on each hop, and no two hops in earshot of one another can transmit at the same moment. A mesh reaches further and carries less. That is not a flaw to be engineered away; it is what one radio on one channel means, and a mesh does not change it: more boxes buy you coverage, never more callers.
A repeater cannot read what it carries
A box on a fence post is a box somebody could take, so this one matters.
When a board and a sat pair, they agree a key between themselves and nobody else has it. Every frame after that is sealed with it, and the frame's header is signed as part of the seal, so it cannot be rewritten either. The four-digit code the sysopThe system operator: the host who runs a board, sets its rules and looks after it. compares at pairing is what rules out anybody in the middle while the key is being agreed: a box that swapped the two ends' keys would make the two codes differ.
A repeater is not one of the two ends. It never holds that key. It can pass a frame on, drop it or hold it up, and that is the complete list: it cannot read one, change one, or send an old one again. That is a property of how the link is already built rather than a promise about a device nobody has written yet, which is why it is the one thing on this page we can say flatly.
Nor is it believed about the way round
Which leaves the question a mesh asks and a planted route does not. If the network decides the path, then anything in radio range that can make itself look like a good next hop can pull your traffic through itself. It still cannot read a word of it, but it can drop it, and that is enough to be worth stopping.
The answer is to keep every word about routes inside the same envelope the pictures are already in. A box's report of what it can hear goes to your board sealed under the key only those two share, and your board is the only thing that ever reads one. The board's reply, telling that box its place and who its neighbours are, comes back the same way. So no box ever takes another box's word about anything, and nothing said out loud on the air about who can reach what is believed by anyone.
Two consequences are worth saying out loud, because they are what the shape buys:
- A link counts only when both ends report it, each in its own sealed report, and it is priced at the worse of the two. Somebody with their own ESP32 in your field can make a path look worse than it is, which is only jamming by another name, and cannot make one look better. They cannot attract your traffic.
- It needs no new secret. There is no shared network key sitting in a box on a post waiting to be read out over a USB cable, nothing to hand round when you add a box and nothing to change when one is stolen. Forgetting one pairing is the whole of it, because nobody else ever trusted that box about anything.
What none of it stops, said plainly: a box that carries your traffic can always drop it, which is the same as switching it off. The answer to that is the mesh noticing and going round, and a sysop forgetting it.
Why this suits a camera better than a terminal
A photograph that arrives a few moments later is the same photograph. A timelapse frame, a temperature, a motion alert: none of them minds waiting, and none of them is being watched while it travels. Those are the things a mesh is for, and they are what the first repeater should carry.
Keystrokes are the opposite. A caller typing into a board judges it entirely on how fast their own letters come back, and delay is the one fault a terminal cannot hide. Every hop adds some, and a route several boxes long adds it over and over.
Carrying a caller's own line over the air is wanted too, and it is the harder half. Rob has asked for it: a gateway sat is being built to bring callers in over the link, and repeating that is on the list. But whether a mesh can carry a session and still feel like a board is an open question nobody has measured, and until somebody has, this page is not going to claim it can.
What exists in this shape already
One thing worth knowing, because it is real today and reads a little like a mesh: a single camera sat can be shared by up to five boards.
Each board pairs with the sat separately and holds its own key, so no board can open another's pictures, and all of them have to be on the same Wi-Fi channel, which in practice means behind the same router. That is firmware 1.2.0 and it is on the camera sat's page.
It is not a repeater. Nothing is passed on by anybody; every board talks to the sat directly. But it is the same one-channel rule showing up again, and it is a good way to see the rule before the repeater asks you to live with it.
Where it stands
Under Later on the roadmap, with no date, alongside remote control, Home Assistant and sats of your own. The link protocol is published with the firmware, so if you want to argue with the design above, or build something of your own that speaks it, everything you need is there.