MeshCore/docs/radio_profiles.md

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Two LoRa profiles on one radio

radio2 lets one LoRa transceiver alternate between two frequencies or modulation settings. It is useful for listening to two networks, or keeping your usual channel available during a LoRa firmware update.

There are at most two active profiles. tempradio temporarily replaces radio; tempradio2 temporarily replaces radio2. These are time-shared receive windows, not simultaneous receivers. Receiving or transmitting a packet on one profile makes the other unavailable until that packet finishes.

The second-profile commands are shared by repeater, Companion, room server, sensor and standalone terminal-chat firmware with a LoRa radio. ESP-NOW-only devices reject LoRa profile commands. KISS is a raw host-controlled modem: it exposes equivalent RAM-only binary SetRadio2/SetTempRadio2 commands and logical KISS Data ports, documented in the KISS modem protocol. It does not use the Mesh CLI's persistent profile file or Mesh retry queues.

Quick setup

Keep the primary channel configured with radio, then add the second:

set radio2 910.5,500,8,5,rx
get radio2
get radio2.status

The tuple is frequency in MHz, bandwidth in kHz, spreading factor, coding-rate denominator, mode, optional preamble in symbols. 5 means coding rate 4/5.

Mode	Receive on profile 2	Transmit on profile 2
rx	Yes	Only infrastructure replies explicitly configured with tx.reply ... force
rxtx (also rx&tx)	Yes	Yes
off	No	No

For transmission on both permanent profiles:

set radio2 910.5,500,8,5,rxtx

The same encoded message is queued separately for each allowed transmit profile. Each has its own direct/flood retry slots and channel-busy backoff. A forwarding echo on one profile cannot cancel the other profile's retry. Packet storage and the physical transceiver's airtime budget are shared; exhausted queues can still drop packets.

Keep the main channel during an update

set tempradio2 910.5,500,8,5,rxtx,120
get tempradio2

This enables the second profile for 120 minutes (2 hours). Locally generated LoRa OTA requests use the temporary second profile. Infrastructure OTA responses follow tx.reply below (both TX-capable profiles by default). Ordinary local traffic stays on the primary profile by default. Use an OTA-capable build and the usual OTA setup on every participating node; a temporary profile does not add OTA support to firmware built without it.

Local settings take effect after a short reply allowance. On repeaters, immediate remote radio2/tempradio2 changes (including off) wait until their exact reply copies finish, with at least one successfully transmitted. A reply that cannot be queued or whose copies all fail cancels the change. Queued replies have a five-minute deadline; an already-transmitting copy may finish under the normal radio watchdog. This confirms transmission, not reception by the remote client.

Permanent remote changes are prepared in an uncommitted file before replying; the saved configuration is replaced only after reply transmission. If that replacement fails, the old channel remains active and the commit retries. Local get radio2.status reports this pending state. Roles without the tracked remote reply path require local USB for these immediate secondary-profile changes.

Temporary periods and schedules live in RAM and disappear on reboot. Waiting for a reply does not extend a temporary lease. Timer expiry also uses monotonic time, so setting the clock backwards cannot extend a temporary session.

Repeater, room-server, and sensor replies

These roles default to tx.reply both: locally generated replies are queued on radio and on an active radio2 that permits TX. This includes replies to remote CLI/login/telemetry requests, ACKs, returned paths, delayed GPIO command completion, room subscription posts, and locally served LoRa OTA catalog, manifest, data, proof, and leaves responses. Each copy has its own retry state. Forwarded packets, periodic adverts, sensor pushes, and OTA requests continue to use the normal crossing rules.

get tx.reply
set tx.reply both
set tx.reply both force
set tx.reply radio
set tx.reply auto

Choice	Replies transmit on
both	Primary plus an active rxtx second profile. Default.
radio	Primary only.
radio2	Second only; no primary fallback.
auto	Normal radio2.cross behavior, including permanent/temporary isolation.
off	Neither profile. This also suppresses remote CLI replies and ACKs.

Append force to both or radio2 to allow these replies on an active second profile configured as rx. Without force, rx remains receive-only. Sending the command again without force removes the override. It never turns on radio2 off, changes the saved rx mode, or enables ordinary forwarding/TX there. Existing crossover packet filters still apply to the extra copy.

The explicit choices override radio2.cross, including off and mixed permanent/temporary profiles. radio means the active primary profile, including tempradio; radio2 also includes an active tempradio2. For example, an OTA source can retain its normal channel while allowing OTA and management responses on a temporary receive profile:

set tempradio2 910.5,500,8,5,rx,120
set tx.reply both force

The source must have OTA support and an active temporary-radio session as usual. A node fetching an update still needs rxtx for its OTA requests. Forcing replies does not change OTA's receive gates, scan timing, or preambles.

This setting survives reboot; older saved profiles adopt both without force. The getter reports when the chosen second profile cannot transmit. Already queued replies retain their choice; disabling/changing a profile invalidates stale queued packets. A parameterized repeater tempradio command waits for both admitted reply copies to drain before changing the primary settings; at least one must transmit successfully. Those tracked replies omit alternate paths and transport retries so no late success copy can outlive the handoff. Queue capacity and the shared transceiver's airtime budget still limit delivery. OTA data/proof admission counts both copies against its queue credit and reserves receive capacity before allowing the response.

Companions use the per-contact/channel choices below; tx.reply is an infrastructure setting.

Companion messages on both profiles

To send ordinary Companion messages on both radio and an active tempradio2, configure the temporary profile in rxtx mode and enable crossing:

set radio2.cross on
get tempradio2
get radio2.cross
get radio2.status

rxtx permits transmission on the second profile; radio2.cross on copies new messages between the two profiles. TX=a,b reports primary and secondary transmit counts. Crossing also applies to OTA traffic.

The crossing setting is saved and remains enabled after the temporary session ends or the node reboots. Run set radio2.cross auto to restore the default isolation between permanent and temporary profiles. The firmware picker's Companion tempradio2 instructions include both choices and the status commands.

Companion TX routing by contact or channel

Companions can save a transmit choice for each contact and each configured channel. The commands apply to messages sent from the phone app, USB/BLE/TCP Companion clients, and the text terminal:

set tx.user "Alice Jones" radio2
get tx.user "Alice Jones"
set tx.channel 0 both
get tx.channel 0
set tx.channel #wardriving radio
get tx.channel #wardriving

Channel indices match the app and the terminal's channels list; Public is normally slot 0. Names must match exactly, including capitalization and any leading #. Quotes always select a literal name, so "1" is a channel named 1, while unquoted 1 selects slot 1. Quote contact names beginning with key: to distinguish them from public-key selectors. Duplicate names are rejected: use the channel index or a contact's public key instead.

Choice	Locally addressed traffic transmits on
auto	Existing behavior, including radio2.cross and temporary-profile isolation. This is the default.
radio	The primary profile only.
radio2	The second profile only; sending fails if it is off or RX-only.
both	The primary profile and the second profile whenever the second is enabled for TX.
off	Neither profile for this contact/channel. Reception stays enabled.

Explicit choices override radio2.cross, including off and the isolation between a permanent and temporary profile. They do not turn on radio2 or change its rx/rxtx mode. For example, leave radio2.cross auto and use set tx.channel 0 both to send Public messages on both radio and an active tempradio2, while other channels keep their default routing.

radio means the currently active primary profile, whether permanent or tempradio; radio2 similarly includes tempradio2. There are still at most two active profiles. Getters show the saved choice and active= for newly initiated messages with the current profile configuration. A temporarily unavailable second profile is reported explicitly.

Contact selection uses the full stored public key after resolving a unique name or key prefix. It never routes by the short on-air destination hash. For key selection, prefix 12–64 hexadecimal digits (whole bytes) with key::

set tx.user key:0123456789AB radio2
get tx.user key:0123456789AB

Replace the example prefix with your contact's key; use more digits if it is ambiguous. get tx.user and get tx.channel report override counts and query syntax. To return a target to the global behavior:

set tx.user "Alice Jones" auto
set tx.channel 0 auto

A user's setting covers addressed texts, login/CLI/telemetry requests, replies, ACKs, and returned paths to that contact. Thus off also prevents ACKs to that contact. Channel settings cover group text and group data, including an explicitly routed group datagram. Contact choices do not filter other people's messages inside a group channel. Adverts, raw traces, raw packets, and OTA packets without a contact/channel destination retain global routing. Packets and their retries already queued retain the choice used when created; changing or disabling the radio profile still invalidates stale queued work. Message timeout estimates use the selected profiles' airtime, independently of the scanner's current receive profile.

Choices survive reboot and normal phone-app updates to the same contact or channel key. Replacing a channel's key or deleting/replacing a contact clears its choice. They use reserved bytes in existing saved records, so record sizes and the phone protocol are unchanged. Older firmware ignores these bytes and may reset the choices when it saves the records.

Companion channel-name routing aliases

Companions recognize the case-sensitive prefixes r2- and mt-, immediately after the optional leading #. Keep the prefix in the app's displayed name. For MeshCore aliases, the firmware strips exactly one prefix when deriving an automatic hashtag key:

#emergency       -> hashtag key for #emergency
#r2-emergency    -> the same key for #emergency
#mt-emergency    -> the same key for #emergency only in MeshCore fallback mode

Only the app's automatic, name-derived hashtag key is normalized; a supplied private key is not replaced. Non-hashtag names such as r2-Private also retain their supplied key. Empty or nested prefixes (r2-, #r2-mt-emergency) are rejected. MeshCore hashtag names remain case-sensitive.

When radio2 is configured (rx or rxtx), r2- binds the channel to radio2 for both send and receive, including emergency retransmissions. It overrides global crossing and cannot be changed with set tx.channel; rename the channel to remove the binding. RX-only radio2 cannot send. If radio2 is off/unconfigured, ignore the routing prefix and use ordinary MeshCore routing instead. The key stays the same as radio2 is enabled, disabled, or a temporary window expires.

If both the ordinary and r2- slots have the same key, a packet received on radio2 selects the r2- slot; a packet received on radio1 selects the ordinary slot. Global packet deduplication still delivers each packet once, not once in each slot. Receiving a radio2-only channel on the wrong profile does not mark that authenticated packet seen, so it can still arrive later on radio2.

The saved channel record retains the original displayed name and app-supplied key for editing and sharing. Runtime copies resolve the actual wire key. Repeater/room/sensor hashtag behavior is unchanged; those nodes can join the canonical MeshCore channel (#emergency). Older Companion firmware does not recognize these aliases.

Meshtext channel chat

MESH_ENABLE_MESHTEXT_CHAT enables the text-only Meshtext backend in the Companion. It defaults on only for ESP32-S3 Full Companion builds using SX1262 LoRa, not an ESP-NOW primary. Other builds default off. This is not a replacement for stock peer firmware or a cross-protocol bridge.

In an enabled build, an mt- name always requests Meshtext, even if radio2 is off or setup is blocked. It never falls back to sending MeshCore frames. In a feature-disabled build, mt- remains an ordinary MeshCore naming alias while radio2 is off; with radio2 configured, MT channel changes/sends are unsupported. The r2- MeshCore behavior above is unchanged in either build.

With the region configured, join #mt-longfast, for example, through the app's normal hashtag-channel editor. A recognized preset name selects the stock peer channel name (LongFast) and, only for an automatically name-derived hashtag key, the expanded public AQ== key. This public key is not a secret. An explicitly supplied private AES-128 or AES-256 key stays private and unchanged. A custom name such as mt-Private uses the exact tail (Private) as its wire name and the supplied key; custom wire names are limited to 11 bytes and need a manual radio2 profile or another MT channel with a recognized preset. Preset names are ASCII case-insensitive; the mt- marker is still case-sensitive.

Recognized aliases and modulation are:

Alias tail	Stock wire name	BW (kHz)	SF	CR
shortturbo	ShortTurbo	500	7	5
shortfast	ShortFast	250	7	5
shortslow	ShortSlow	250	8	5
mediumturbo	MediumTurbo	500	9	5
mediumfast	MediumFast	250	9	5
mediumslow	MediumSlow	250	10	5
longturbo	LongTurbo	500	11	8
longfast	LongFast	250	11	5
longmod or longmoderate	LongMod	125	11	8
longslow	LongSlow	125	12	8

The selected region must have room for the bandwidth; for example, 500 kHz presets are unavailable in the supported EU868 plan. Use these CLI commands:

get mt.status
get mt.region
get mt.slot
get mt.hops
get mt.node
get mt.shortname
set mt.node !12345678
set mt.node default
set mt.region auto
set mt.region us
set mt.slot 0
set mt.hops 7
set mt.shortname HALO
set mt.shortname default
send mt.nodeinfo 0
get radio2
set radio2 auto

mt.region accepts auto, us, eu868, eu433, or anz. auto infers US only from a primary frequency at least 902 MHz and below 915 MHz, EU868 from 869.4–869.65 MHz, and EU433 from 433–434 MHz. The US/ANZ overlap at 915–928 MHz is ambiguous: explicitly select us or anz. mt.slot is a 1-based frequency slot, or 0 for the stock preset-name-derived slot; unavailable slots are blocked. Check get mt.status after configuration; a successful settings save does not mean the MT backend is active.

Outgoing MT messages default to a hop limit of 7. set mt.hops <0..7> changes this budget, and get mt.hops or get mt.status shows it. 0 sends only the initial over-air hop with no forwarding budget; larger values permit protocol-compatible peers to forward within that budget. The Companion itself still does not relay MT packets.

get mt.node shows the effective Meshtext sender node ID. By default it is SHA-derived from the MeshCore public identity and remains stable for that identity. set mt.node !12345678 sets a saved override; exactly eight hexadecimal digits are required, with or without the leading !. Input is hexadecimal, not decimal, and is never silently truncated. IDs 00000000 through 00000003 and ffffffff are reserved and rejected. set mt.node default clears the override and restores the identity-derived ID.

The example ID is illustrative: choose an ID unique among your protocol-compatible peers. Collisions can merge different senders into one identity and interfere with packet deduplication. Changing the MT ID does not alter the MeshCore private key, reset the outgoing packet-ID sequence or send automatic traffic. Settings changes are refused while an MT transmission is pending. Neither node IDs nor text labels are authenticated.

set mt.shortname <label> saves a Meshtext-only NodeInfo name of 1–4 Unicode scalar characters, with valid UTF-8 and at most 16 encoded bytes. Combining characters count separately. get mt.shortname shows the saved/effective name. Stock NodeInfo accepts only four UTF-8 bytes, so the effective wire name is the longest complete UTF-8 prefix that fits. The saved value is not changed. set mt.shortname default clears the override and uses the last four hexadecimal digits of the effective MT node ID. This does not change the MeshCore node name, add a label to chat text or transmit anything.

send mt.nodeinfo <channel slot> explicitly queues one standard NODEINFO_APP broadcast on the selected configured MT channel. The slot is the Companion channel index, not mt.slot (the frequency slot). The packet contains the actual sender ID, the global MeshCore node name as its long name (UTF-8-safe truncated to 24 bytes), the effective short name, CLIENT_MUTE (no relaying), and the no-DM flag. It omits MAC, public keys and unsupported metadata. The usual radio2 TX-mode, pending-TX, airtime and profile guards apply. The reply says queued, not delivered or acknowledged.

There are no automatic NodeInfo advertisements: not at boot, on a timer, when names change, when chat is sent, or in response to received packets. Received NodeInfo is still ignored; this backend does not maintain a node database.

Region, frequency slot, hop limit, shortname and node-ID override are saved atomically together; changing one preserves the others. Current 40-byte MT03 settings include both overrides. New firmware accepts valid legacy MT01/MT02 settings and defaults the shortname to the sender-ID suffix and the node ID to the MeshCore identity; MT01 also defaults the hop limit to 7. Older MT firmware cannot read MT03, so downgrading does not preserve access to these settings. Invalid or unsupported stored settings block MT operation rather than silently selecting another network.

Private channels can be provisioned directly through the Companion CLI:

set mt.preset <longfast|shortturbo|...>
set mt.channel <slot> <mt-name> <32/64 hex digits|AQ==>
get mt.channel <slot>
delete mt.channel <slot>

set mt.preset accepts the recognized presets above and explicitly saves a manual rxtx radio2 RF tuple using the current region and frequency slot. It is not an automatic owner: deleting the channel does not remove that saved RF configuration. Set region/slot first; changing them later does not overwrite the manual frequency, so rerun set mt.preset if you intend to retune it.

set mt.channel accepts a 32-digit hexadecimal AES-128 PSK, a 64-digit hexadecimal AES-256 PSK, or the literal AQ== for the public key. It does not accept arbitrary Base64 private keys. The stored format interprets an all-zero upper 16-byte half as AES-128, including in a 64-digit input; use a nonzero upper half for AES-256. Slot numbers are zero-based and build-specific, as in the app. get mt.channel reports name, wire name and AES size, never the PSK. The firmware console masks key input echo; keep your client-side logs and stored keys private as well. SET and DELETE save transactionally and restore the previous channel if storage fails. DELETE applies only to an MT channel, not a MeshCore slot.

For a private channel named Team on a protocol-compatible peer:

set mt.region us
set mt.preset longfast
set mt.channel 1 mt-Team <your-32-or-64-hex-digit-key>
get mt.channel 1
get mt.node
set mt.shortname HALO
get mt.status
send mt.nodeinfo 1
channel 1 Hello

Replace the key placeholder with your actual hexadecimal PSK and send after get mt.status reports active. The peer must use the same preset, frequency, PSK and exact case-sensitive wire name Team; mt- is only the local marker. Alternatively, set mt.channel 1 mt-longfast <your-key> preserves a private PSK but uses wire name LongFast and can acquire automatic RF without set mt.preset, provided radio2 automatic ownership is permitted. This route is available for both 128-bit and 256-bit private keys even when the stock app cannot provision or export the latter.

When radio2 was never manually configured, a recognized preset can acquire an automatic rxtx profile. Its RF tuple is RAM-only and stays available for RX while the required channels exist. Removing the last MT channel, losing its last recognized-preset dependency, or detecting a conflict releases only the automatic profile. Explicit manual RF settings are retained: named aliases must match their BW/SF/CR and fit the selected region, but do not overwrite their frequency. The runtime MT overlay uses its required 16-symbol preamble; the saved manual preamble is retained.

set radio2 off is an explicit manual veto, including after reboot. Older saved off profiles are conservatively treated as manual. Local set radio2 auto clears the saved manual RF/off choice and permits automatic ownership after two seconds; it rejects pending changes, leases and schedules rather than cancelling them. get radio2 distinguishes auto-owned, off (manual) and off (automatic allowed). Temporary profiles, scheduled changes and reply commit barriers take precedence and can suspend MT operation. Automatic cleanup does not undo later manual edits.

All MT channels share this one secondary modem profile. Different recognized presets, or mixing any MT and r2- channels, are rejected instead of selecting whichever channel was edited last. Loaded conflicts also block MT traffic. Neither radio2.cross on nor MeshCore channel routes cross MT frames between protocols.

The app uses its existing channel index/text commands and receive events. Outgoing MT chat is plain text exactly as entered, with the sender node ID in the standard radio header. It contains no custom name envelope or NodeInfo. Incoming text uses the exact sender-ID prefix !12345678: before the received payload when passed to the MeshCore app. Changing the shortname only changes future manually requested NodeInfo, not chat or the packet's sender ID; set mt.node changes the actual Meshtext sender ID. Neither setting change emits advertisements. A successful send response means queued, not acknowledged by a remote node. This backend does not relay MT packets or provide ACKs, administrative commands, direct messages, automatic node-info adverts or a node database. MeshCore emergency forwarding does not apply to MT traffic. Interoperability is with stock peers' PSK channel text using AES-CTR, not AES-CCM. AES-CTR channel traffic is not authenticated; successful decoding is not proof of sender identity.

The codec supports AES-128 and AES-256 and up to 228 UTF-8 bytes of wire text, without an added label/node-ID prefix. The standard app channel editor still provisions 16-byte keys. An MT-only 32-byte binary SET/opt-in GET extension is available for capable clients, with protection against legacy 16-byte edits truncating an existing 256-bit key; see Companion protocol. This does not give stock apps seamless 256-bit provisioning or sharing. Current V3 Companion receive events carry at most 165 text bytes including the node-ID prefix; longer incoming MT text is UTF-8-safe truncated for the app.

Radio1 and radio2 still time-share one physical radio. The device cannot receive either network while tuned to the other or transmitting; long MT airtime, particularly LongFast, can leave substantial MeshCore receive gaps. The compatible protocol's fixed short preamble also does not provide the scan-aware long preamble described below. Do not treat this as continuous coverage of both networks or guaranteed message delivery.

Choose whether traffic crosses between profiles

get radio2.cross
set radio2.cross auto
set radio2.cross on
set radio2.cross off

Active primary	Active secondary	auto (default)	on	off
radio	radio2	Cross	Cross	Isolated
tempradio	tempradio2	Cross	Cross	Isolated
radio	tempradio2	Isolated	Cross	Isolated
tempradio	radio2	Isolated	Cross	Isolated

This table describes MeshCore profiles. A Meshtext secondary profile is always isolated, including with radio2.cross on.

These are the global rules used by Companion targets set to auto; an explicit contact/channel choice above overrides crossing for its own outbound packets. Ordinary crossing respects rx. The infrastructure-only tx.reply ... force override above permits locally generated replies on that profile. With crossing allowed, a packet received there may still be forwarded on the primary profile. Existing routing, forwarding and packet-filter settings apply. An RX-only tempradio2 also blocks locally generated OTA requests under auto or off; they do not fall back to the normal primary channel. Use rxtx for a fetching node that needs to exchange requests and data. Infrastructure OTA responses follow tx.reply independently of this crossing table.

Preamble

Append the preamble to the end of a command:

set radio2 910.5,500,8,5,rxtx,88
set tempradio2 910.5,500,7,5,rxtx,120,128
set radio 909.5,62.5,7,5,32
set tempradio 909.5,62.5,7,5,120,32

Existing primary radio, tempradio, radioat and tempradioat commands accept the optional trailing preamble where those primary commands are supported by the role. Getters include the preamble. Omit it, or use auto/0, to calculate it automatically. Explicit values are used as entered, subject to the radio's limits and safe airtime arithmetic.

Automatic dual-profile preambles round up to a multiple of eight, with a 32-symbol minimum and a 128-symbol maximum. When a second profile activates, the radio first self-tests four successful RX-to-RX switches in each direction using the actual tuples. It defers the test while receiving, transmitting or busy, and never counts a failed switch. The 128-symbol automatic preamble is provisional until the test completes. The largest successful hop, rounded up with a 10% guard, then supplies the per-switch allowance for both the automatic preambles and the scan dwell. There is no fixed switch-time floor. The measurement is reset when either profile changes, including when a tempradio2 session starts or ends; it is not saved to flash. The rapid startup hops briefly interrupt reception on each channel; a new packet beginning during this test may be missed. An already detected packet defers the test instead of being interrupted.

Each idle scan starts with 4.6 symbols on the slower profile, then spends the remaining budgeted time on the faster profile, also with a 4.6-symbol floor. Slower means a longer LoRa symbol (2^SF / bandwidth), regardless of profile number. The slower preamble sets the return deadline. The calculation allows two slow visits within that preamble, reserving the self-tested, 10%-guarded switch time per hop. There is no extra fixed main-loop allowance. Fast-channel transmit preambles include sixteen acquisition symbols. For a primary SF7 / 62.5 kHz profile with a 763 us measured maximum switch (840 us after the 10% guard, from the BLE-on T1000-E trial):

Secondary profile	Automatic secondary preamble	Previously tested explicit preamble	Primary preamble
SF9 / 500 kHz	32	32	32
SF8 / 500 kHz	40	64	32
SF7 / 500 kHz	64	80	32

With preamble 32 on that slower profile, its visit is 9.421 ms and the faster visit is 21.667 ms, plus the actual switching time. Increasing the slow preamble also increases the time available on the fast channel. If the symbols are equal in length, the primary profile goes first. Detected packets hold the current channel until reception finishes.

The SF8 / 500 kHz value is calculated from the same formula as every other profile; the older pair-specific 88-symbol floor has been removed. The explicit values come from historical production validation: the final fast-channel attempts each received 50/50 packets at 4.8 slow symbols. Automatic values use the measured switch allowance below. Those explicit-preamble tests used the older 4.8-symbol policy; they do not validate the newer 4.6-symbol slow dwell. The 4.6/0.3 ms two-profile bench received 197/200 at SF7/62.5 + SF8/500 with explicit 32-symbol preambles. The newer four-channel 5.1/6.1/7.7 tests also had misses, so this is a timing policy, not a claim of zero packet loss. The automatic fast preamble covers the blind interval during the slow visit, both switches and the acquisition margin. These settings do not guarantee reception during overlapping packets or long pauses in the firmware loop. Transmitters on each channel also need a long enough preamble. Changing the receiver's setting does not lengthen packets sent by other nodes.

Chirp calculator and warnings

get radio2.timing (alias get radio.timing) reports the active pair in radio,radio2 order: dwell in chirps, recommended preambles in symbols, and the switching/loop allowances. Before calibration it reports timing self-test pending and the provisional preambles. On nRF52 boards, enabling radio2 uses RTC2 for both retune timing and scan visits (about 31 us resolution); turning radio2 off stops RTC2 and returns to the usual micros() clock. Previously, the nRF52 micros() fallback counted 1,024 Hz RTOS ticks: a real sub-millisecond retune could be reported as exactly 977 us, and two ticks as 1,953 us. Those old numbers are timer artifacts, not measured RF costs. For SF7/62.5 on radio and SF8/500 on radio2, one live BLE-on read returned:

> chirps=4.60,42.84; need=32,40; switch=706us; loop=0us; test=4/4,4/4 ready; WARN recommended preamble: radio2=40

Later good hops in another BLE-on trial raised the measured maximum to 763 us (840 us with the 10% guard); the recommendation stayed at 40 symbols.

The measured switch duration is wall time, so an interrupt during the hop is included. Bluetooth's SoftDevice may still preempt application code; this clock correction does not stop it. Ordinary Companion/USB work in the main loop does not run inside the synchronous retune, but it can delay when the next scan visit begins. The zero fixed loop allowance is not a guarantee of lossless reception under arbitrary application load.

WARN recommended preamble identifies each profile whose recommendation exceeds the standard 32 symbols or its explicitly selected value. For example, with SF7/62.5 on the primary profile, set radio2 910.5,500,7,5,rx,32 initially replies with timing self-test pending. Once active and measured, get radio2 warns:

> 910.500,500.000,7,5,rx,32; WARN recommended preamble: radio2=64; short override: radio2

Successful set radio ... replies also include the recommended preamble for each affected profile, calculated with the requested settings. A short override note identifies an explicit value below the estimate; it is not silently rewritten. Warnings are also included in profile settings/getters, scan info, temporary settings and schedule acknowledgments. These preamble-bearing replies also include switch=547us (or the current measured value) after the self-test for that exact profile pair. The first ACK for a new pair says timing self-test pending instead: it is sent before activation, so it cannot contain the future measurement. Query get radio2 after activation to see the measured value beside the resulting preamble. off disables the dual-profile warning. get radio2.status shows self-test progress and the resulting guarded switch budget; its separate max field remains a lifetime diagnostic that can include failed/rolled-back retunes and is not used for calibration. If the recommendation exceeds 128, it additionally reports WARN need >128; an automatic preamble stays at 128, which may not be enough for reliable reception on that pair. Explicit preambles are not rewritten and still use the radio's ordinary validation limits. A timing readout does not change settings or transmit a packet.

The shared RadioProfiles::calculateChirpTiming() function accepts both tuples, optional visit times in microseconds, a per-switch allowance and loop margin. Using microseconds throughout:

T[i] = 2^SF[i] * 1000 / BW_kHz[i]
slow = profile with the longer T (radio wins ties)
L[slow] = max(requested_visit_us[slow], ceil(4.6 * T[slow]))
L[fast] = max(requested_visit_us[fast], ceil(4.6 * T[fast]))
O    = 2 * switch_us
C    = L[radio] + L[radio2] + O

P[slow] = round_up_to_8(max(32, 2 * C / T[slow]))
P[fast] = round_up_to_8(max(32, (L[slow] + O) / T[fast] + 16))

Automatic selection uses the minimum visits to choose a preamble, then allocates the fast visit from half the slow preamble's duration. Diagnostics feed the actual allocated visits back into the same function, including longer visits caused by an explicit slow preamble. Too-short slow preambles that cannot fit both minimum visits remain rejected by the existing configuration validation.

The automatic scheduler uses these same role-specific minima and computes:

slow_dwell = ceil(4.6 * T[slow])
fast_dwell = max(ceil(4.6 * T[fast]),
                 floor(P_configured[slow] * T[slow] / 2 - slow_dwell - O))

For the tested SF7/62.5 + SF8/500 pair with slow preamble 32, this yields 9,421 us slow and 21,197 us fast (41.40 fast chirps) with the 1,075 us guarded switch allowance above. Swapping radio and radio2 swaps the allocations automatically.

Production scheduling and automatic preambles use the self-tested maximum successful switch plus 10%, without an additional fixed loop allowance. Subsequent successful hops can only raise that allowance until the next profile change. The measured recommendation is rounded up to eight symbols and capped at 128 for automatic settings. The calculator and warnings retain the uncapped recommendation so a slow board is not shown as safe merely because it hit the limit. Older V4 tests peaked at 836 us (827 us in the 4.6/0.3 ms run), and Indicator reached 8428 us; these are historical measurements, not default budgets for other boards. The model preserves two slow-profile return opportunities and the existing 16-symbol fast-profile acquisition allowance. These are conservative policies, not a fitted success curve, and neither packet overlap nor arbitrary application stalls can be made safe by a finite preamble recommendation.

See the implementation and validation notes.

Schedule the second profile

Use UTC Unix timestamps (seconds), or +N for N whole minutes from now:

set radioat2 910.5,500,8,5,rxtx,START[,PREAMBLE]
set tempradioat2 910.5,500,8,5,rxtx,START,END[,PREAMBLE]
get radioat2
get radioat2 1
get tempradioat2
get tempradioat2 1
del radioat2 1
del tempradioat2 all

Replace START and END with timestamps or +N, and the optional PREAMBLE with a number; omit the square brackets. Each schedule family has four slots. Times must be in the future and within 24 days. Overlapping temporary second-profile sessions are rejected. radioat2 changes the saved second profile when it starts; tempradioat2 restores the saved profile at its end. Pending schedules do not survive reboot.

For example, set tempradioat2 910.5,500,8,5,rxtx,+5,+15 starts in 5 minutes and restores in 15 minutes (10 minutes active). Both offsets are measured from the same node-clock snapshot when accepting the command, not from each other. set radioat2 910.5,500,8,5,rxtx,+5 schedules a saved change in 5 minutes. Offsets must be positive whole minutes. Absolute and relative endpoints can be mixed; bare numbers still mean UTC seconds. Existing clock requirements apply.

Return to one profile

set radio2 off

This saves the disabled state and cancels all second-profile temporary activity and schedules.

set tempradio2 off

This ends temporary second-profile activity, cancels its temporary schedules and restores saved radio2. If the saved second profile is off, this returns to one profile. Packets/retries bound to an expired or changed session are discarded.

Power saving and diagnostics

Dual mode suspends RX power saving and MCU idle sleep so receive visits can run promptly. The saved RX power-saving setting returns when profile 2 is off. The scan uses normal receive, following the CAD/RX measurements, with the updated 4.6-symbol dwell on the slower channel, followed by the remaining fast-channel visit. It does not use CAD for scanning. The separate CAD check before an initial transmission still follows cad.

SX1262 dual-profile mode keeps the oscillator running in XOSC standby between visits, so each retune does not need to restart the TCXO. It restores the prior standby policy when returning to one profile, together with the saved RXPS setting. Radio reinitialization temporarily uses RC standby until the TCXO has been configured again. Other radio families retain their existing behavior. This does not disable the TCXO supply or its initial startup delay, and it is not conditional on 500 kHz bandwidth. Keeping the oscillator on uses additional power during the short standby intervals.

The switch-time self-test is not a forced settling delay or a proof of RF acquisition. The earlier standalone keep-warm scan experiment averaged about 1.19 ms of overhead per hop (scan-cycle time minus both receive windows, divided by two). That experiment used a leaner receive path; it is not a measurement or guarantee of the production implementation. Measure the target board before shortening its timing margins or transmit preambles.

The production-path XIAO timing test measured 1.434 ms average / 1.467 ms maximum with warm standby, compared with 3.166 ms average using RC standby: about 1.732 ms saved per hop. It covered 12,000 retunes across SF7/8/9 at 500 kHz paired with SF7/62.5 kHz. These measurements include observing BUSY low, but exclude application/UI scheduling and are not a packet-delivery qualification or a guarantee for other boards, especially those using I/O expanders.

A same-image follow-up batching SF/BW/CR into one modulation command reduced warm switching from 1.444 ms to 1.158 ms average (batched maximum 1.198 ms), saving another 0.286 ms / 19.8%. RadioLib's modulation caches and LDRO calculation remain synchronized; frequency, preamble, packet guards, and RX restart are unchanged. A later HIL-only screening tested redundant standby/IRQ/buffer/packet setup and SPI transfer changes. Its fastest candidate measured 0.535 ms mean on XIAO but 8.203 ms on the Indicator, whose radio GPIOs go through an I2C expander. The validated production implementation now opts XIAO S3 WIO and Indicator LoRa into buffered 8 MHz SPI and a guarded fast-RX state machine. The heltec_v4_kiss_modem and Station_G3_ESP32_kiss_modem targets use the same guarded path only for KISS dual-profile scanning; their normal board roles keep their established HAL/timing policy. V4 uses its existing 160 MHz role override and Station G3 uses its base 240 MHz setting, but both still need an exact-image hardware timing check before a nominal 600 µs target is claimed. It skips redundant standby, IRQ mapping, buffer-base writes and modem queries only during an owned continuous RX-to-RX retune. Preamble/packet parameters (including the IQ workaround), stale-IRQ clearing, RX commands and BUSY waits remain. TX, CAD, sleep, reset, RXPS and failed commands revoke reuse; failed RX startup rolls back the profile. Sleep entry uses standby and wake restores the existing TCXO voltage/delay. Other variants do not opt in to faster SPI or the fast-RX state machine. Within a valid owned fast-RX retune, identical acknowledged SF/BW/CR/LDRO settings now reuse the previous modulation command: frequency-only hops omit SetModulationParams (0x8B). A changed effective LDRO value also forces a write, including when automatic LDRO policy changes. Ordinary setters and lost RX context invalidate that acknowledgement; initial setup, reset, sleep, failed commands and full RX setup conservatively reapply the tuple. Frequency, preamble/packet setup, IRQ clearing and BUSY checks are unchanged. This follow-up has same-image hardware measurements: frequency-only hops averaged 0.452 ms on XIAO and 7.601 ms on Indicator. The mixed-bandwidth timing figures above predate it. Four-channel SF6 scans still missed packets; faster switching is not proof of loss-free acquisition. See production and USB validation for current measurements, lifecycle tests and limitations. The Indicator result shows why each board now measures its own switch time. That measurement adjusts automatic preambles and dwell, but it cannot verify RF acquisition or lengthen packets transmitted by other nodes.

Single-channel noise-floor calibration and RSSI interference comparison are suspended while scanning. Retries use the radio's preamble/header activity indicators. LR2021 extra-SF side detectors are suspended and restored as well.

get radio2.status reports the active second-profile mode, MeshCore RX/TX counts for each profile, switch count, switch failures, longest measured switch and both effective preambles. A long switch time or rising error count indicates that the chosen settings need investigation on that board.

get radio2.scan shows which profile goes first, the two idle receive-window lengths in microseconds, and both effective preambles. It reports off in single-profile mode.