Editing SimTX API v24/Packets/TxUpdate

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{{SimTX packet v24
| name = TxUpdate
| id = 19
| hex = 0x13
| direction = c2s
| session = [[SimTX API v24/Transmitter session|Transmitter]]
| size = 1 + 9 × count bytes
| permission = None
| reply = [[SimTX API v24/Packets/TxUpdateAck|TxUpdateAck]]
| group = transmitter
}}
'''TxUpdate''' changes transmitter settings while the station is on air, without reconnecting. It uses the same field IDs as the [[SimTX API v24/Packets/TransmitterSessionRequest|TransmitterSessionRequest]], restricted to numeric fields. The server answers every TxUpdate with a [[SimTX API v24/Packets/TxUpdateAck|TxUpdateAck]].

== Layout ==
{| class="wikitable"
! Field !! Type !! Description
|-
| <code>packetId</code> || <code>u8</code> || Always <code>19</code>.
|-
| <code>count</code> || <code>u8</code> || Number of fields, 1–64.
|-
| <code>fields</code> || <code>count × { u8 fieldId, i32 length, f32 value }</code> || <code>length</code> must be 4. A field with any other length (up to 1,024) is skipped.
|}

== Live fields ==
{| class="wikitable"
! ID !! Field !! Accepted values
|-
| 5 || <code>frequencyHz</code> || 1,000 Hz to 3 GHz. Outside: refused.
|-
| 6 || <code>powerWatts</code> || ≥ 0. Reduced to at most 1,000,000 W and to the account's <code>tx.pa_limit</code>. Negative: refused.
|-
| 10 || <code>txBandwidthHz</code> || 10 Hz to 10 MHz. Outside: refused.
|-
| 11 || <code>audioLowCutHz</code> || ≥ 0; values above 5,000 are reduced to 5,000. Negative: refused.
|-
| 14 || <code>finalDriveDb</code> || −40 to 40 (clamped).
|-
| 15 || <code>paHeadroomDb</code> || 0.1 to 40.
|-
| 16 || <code>audioCompressionDb</code> || 0 to 30.
|}

Any other field ID is refused in the acknowledgement. Changing the modulation, sample rate, source, location or antenna requires a new session.

== Rate limits ==
* If any update was applied less than 250 ms earlier, the whole packet is refused.
* A frequency change is refused if the previous frequency change was less than 1 second earlier.
* Refused fields are reported in the ack with <code>accepted = false</code>. They are not queued; send them again later.
* At most 16 acknowledgements may be outstanding. A client that keeps sending updates without reading acks is disconnected.

== Example ==
Set power to 50 W and frequency to 7.074 MHz:

<syntaxhighlight lang="text">
13                 packetId 19
02                 count 2
06 00 00 00 04 42 48 00 00      field 6, length 4, 50.0
05 00 00 00 04 4A D7 E1 A0      field 5, length 4, 7074000.0
</syntaxhighlight>

== See also ==
* [[SimTX API v24/Transmitter session#Live updates|Live updates]]

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