yet-another-intercom-hack

yeah, and we still consider ourselves as "evolved" apes, but less pacific/peace-smart than our hairy cousins ..
fingers crossed bullshit 'll stop, but we both know, they ain't have a cat to pet to fully embrace peacefullness ( .. )

For the "damn you SIM800L" issue, I don't know how it happened, but yeah, it seems like so -> when plugged in USB to my laptop, the red light keeps being lit.

I just did what you propose, and I could indeed see the light goes off as I was connecting to either a 3.7V 150mAh battery or a bigger 3.7V 1200mAh, and after plugging in USB, I could connect to it on /dev/ttyACM0 & try 1+2 ;)

'Need a confirmation for a dummy-question-of-mine, though: it's ok to have Bat+V to battery +V, Gnd to battery Gnd, and be connected to USB at the same time ( for Rx /Tx ) ?
I'm pretty new to using batteries in my projects ( yes, true story ;p ), and from what I could read, aside from other things those "3.7V 150mAh 20C batteries" seems, for example, to be most used for powering RC controlled devices motors than uCs ( the "20C" thing ? )

In other words, I don't want to risk the same "shorting 5V to Gnd" using a battery this time ( ' don't want it to be damaged .. or explode :/ )

Anyway, I guess I'll have to work on this Pico with a battery by now, as I really can't replace that diode ;p
Good news is, I'll order another 1 or 2 to to have them handy [ & support ] ;)

With the AT commands, everything was fine except for the text messages, as even when using ATE0\r\n, they're still being split ( the text content resides after all the other crap ).
Now, your workaround seems quite useful, as I could use it to partially construct an obj across cb calls:

var SMS = {};
at.cmd("AT+CMGR=1\r\n", 1000, function cb(d) {
  if (d===undefined) ; // we timed out!
  // d is now the result
  if ( d == "AT+CMGR=1" ) return cb;
  else if ( d.startsWith( "<infos on SMS>" ){
    // populate SMS
    SMS.date = ..
    SMS.senderNum = ..
    return cb;
  }
  else {
    SMS.content = ..
    console.log('AT+CMGR=1 result: ' + SMS);
   }
});

Also, is the following actually doing something or just a nonsense ? ^^

// ( .. )
if ( at.isBusy() ) return cb;
// ( .. )

I'll retry the SMS stuff / updating the wip module in few hours to reflect the tries results, still having a solution to make sure the SIM800L doesn't make the battery explode / burnout Pico stuff 'd be nice to have ( this being said, I actually don't know how I could have those shorted in the 1st place .. )

thanks for the troubleshooting ;p