Syncing multiple transmitters on esp32/RP2 ?

[FransKlip]

Hi, nice library!
I'm starting on a small hobby project using multiple emitters - 3, up to 16 or perhaps 32 - that each send a unique message in sequence (kind of lighthouse idea) at 35 kHz using some suitable protocol, controlled from a single ESP32 or rPi Pico (RP2) program using asyncio.
The 3-emitter setup will use 3 instances of the transmitter object (possible?), each using its own output pin with IR-led.
The other setup's will use a serial-in 8-port or 16-port led driver (or another suitable multiplexer/driver), with the carrier signal on a separate ouput pin might be required. Only a single instance of the Sender object and one single LED output port is used with each time a slghtly different message. The program takes care of selecting the next IR-led for the corresponding message to be sent.

Question: It is not clear me how I can synchronise (step to the next output) transmitions to the different emitters so that they do not overlap.
Is checking the .busy method enough in case of the hardware asynchronously handling the message buffer?
Or should an input port detect if a pulse train is being transmitted?
Is using multiple sender object possible?
Is using multiple receiver objects possible, each using its own input pin?

Suggestion: it would be nice to have a callback facility indicating that the transmission has finished.

[peterhinch]

I think this would require a significant rewrite of the library. Re multiple transmitters, the ESP32 has only 8 RMT channels and the RP2x has a limited number of state machines. Re multiple receivers by default the receiver uses soft IRQ's and soft timers, so there is no obvious resource limit. It stores the arrival times of pulses in an array, then when the burst ends, analyses the data. However if multiple receivers were operating concurrently there could be issues. You might need to use asyncio with pending decodes being queued for decode.

A non-trivial project!

[FransKlip]

Thanks @peterhinch, this solves most of my questions. A 'significant rewrite' never was my intention.
I have to change the setup for a small number of transmitters to use the same external multiplexing: select one transmitter, send its message, wait for message to finish (using asyncio), select next transmitter .... Just a single instance of the Transmitter object is used. And there is only one variant of the hardware and its associated function in the program.
Multiple receivers - say 4 or 8 - might be used, as this will be mounted on a moving Lego car. 4 receivers will make it possible to receive one (or more) sender(s) from anywhere around the car. I will have a look at queuing decode actions later on.