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Full settings (center freq, spread factor, pre-shared secret key etc...) needed to configure a radio for speaking on a particular channel This information can be encoded as a QRcode/url so that other users can configure their radio to join the same channel. A note about how channel names are shown to users: channelname-Xy poundsymbol is a prefix used to indicate this is a channel name (idea from @professr). Where X is a letter from A-Z (base 26) representing a hash of the PSK for this channel - so that if the user changes anything about the channel (which does force a new PSK) this letter will also change. Thus preventing user confusion if two friends try to type in a channel name of "BobsChan" and then can't talk because their PSKs will be different. The PSK is hashed into this letter by "0x41 + [xor all bytes of the psk ] modulo 26" This also allows the option of someday if people have the PSK off (zero), the users COULD type in a channel name and be able to talk. Y is a lower case letter from a-z that represents the channel 'speed' settings (for some future definition of speed)

FIXME: Add description of multi-channel support and how primary vs secondary channels are used. FIXME: explain how apps use channels for security. explain how remote settings and remote gpio are managed as an example


from protobuf message ChannelSettings


  • ChannelSettings




bandwidth: number

Bandwidth in MHz Certain bandwidth numbers are 'special' and will be converted to the appropriate floating point value: 31 -> 31.25MHz


from protobuf field: uint32 bandwidth = 6;


channelNum: number

NOTE: this field is independent and unrelated to the concepts in channel.proto. this is controlling the actual hardware frequency the radio is transmitting on. In a perfect world we would have called it something else (band?) but I forgot to make this change during the big 1.2 renaming. Most users should never need to be exposed to this field/concept. A channel number between 1 and 13 (or whatever the max is in the current region). If ZERO then the rule is "use the old channel name hash based algorithm to derive the channel number") If using the hash algorithm the channel number will be: hash(channel_name) % NUM_CHANNELS (Where num channels depends on the regulatory region). NUM_CHANNELS_US is 13, for other values see MeshRadio.h in the device code. hash a string into an integer - djb2 by Dan Bernstein. - http://www.cse.yorku.ca/~oz/hash.html unsigned long hash(char *str) { unsigned long hash = 5381; int c; while ((c = *str++) != 0) hash = ((hash << 5) + hash) + (unsigned char) c; return hash; }


from protobuf field: uint32 channel_num = 9;


codingRate: number

The denominator of the coding rate. ie for 4/8, the value is 8. 5/8 the value is 5.


from protobuf field: uint32 coding_rate = 8;


downlinkEnabled: boolean

If true, messages seen on the internet will be forwarded to the local mesh.


from protobuf field: bool downlink_enabled = 17;


id: number

Used to construct a globally unique channel ID. The full globally unique ID will be: "name.id" where ID is shown as base36. Assuming that the number of meshtastic users is below 20K (true for a long time) the chance of this 64 bit random number colliding with anyone else is super low. And the penalty for collision is low as well, it just means that anyone trying to decrypt channel messages might need to try multiple candidate channels. Any time a non wire compatible change is made to a channel, this field should be regenerated. There are a small number of 'special' globally known (and fairly) insecure standard channels. Those channels do not have a numeric id included in the settings, but instead it is pulled from a table of well known IDs. (see Well Known Channels FIXME)


from protobuf field: fixed32 id = 10;


Note: This is the 'old' mechanism for specifying channel parameters. Either modem_config or bandwidth/spreading/coding will be specified - NOT BOTH. As a heuristic: If bandwidth is specified, do not use modem_config. Because protobufs take ZERO space when the value is zero this works out nicely. This value is replaced by bandwidth/spread_factor/coding_rate. If you'd like to experiment with other options add them to MeshRadio.cpp in the device code.


from protobuf field: ChannelSettings.ModemConfig modem_config = 3;


name: string

A SHORT name that will be packed into the URL. Less than 12 bytes. Something for end users to call the channel If this is the empty string it is assumed that this channel is the special (minimally secure) "Default"channel. In user interfaces it should be rendered as a local language translation of "X". For channel_num hashing empty string will be treated as "X". Where "X" is selected based on the English words listed above for ModemConfig


from protobuf field: string name = 5;


psk: Uint8Array

A simple pre-shared key for now for crypto. Must be either 0 bytes (no crypto), 16 bytes (AES128), or 32 bytes (AES256). A special shorthand is used for 1 byte long psks. These psks should be treated as only minimally secure, because they are listed in this source code. Those bytes are mapped using the following scheme: 0 = No crypto 1 = The special "default" channel key: {0xd4, 0xf1, 0xbb, 0x3a, 0x20, 0x29, 0x07, 0x59, 0xf0, 0xbc, 0xff, 0xab, 0xcf, 0x4e, 0x69, 0xbf} 2 through 10 = The default channel key, except with 1 through 9 added to the last byte. Shown to user as simple1 through 10


from protobuf field: bytes psk = 4;


spreadFactor: number

A number from 7 to 12. Indicates number of chirps per symbol as 1<<spread_factor.


from protobuf field: uint32 spread_factor = 7;


txPower: number

If zero then, use default max legal continuous power (ie. something that won't burn out the radio hardware) In most cases you should use zero here. Units are in dBm.


from protobuf field: int32 tx_power = 1;


uplinkEnabled: boolean

If true, messages on the mesh will be sent to the public internet by any gateway ndoe


from protobuf field: bool uplink_enabled = 16;

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