Cellular

lock()

The Cellular object does not have built-in thread-safety. If you want to use things like Cellular.command() from multiple threads, including from a software timer, you must lock and unlock it to prevent data from multiple thread from being interleaved or corrupted.

A call to lock lock() must be balanced with a call to unlock() and not be nested. To make sure every lock is released, it's good practice to use WITH_LOCK like this:

// EXAMPLE USAGE
void loop()
{
  WITH_LOCK(Cellular) {
    Cellular.command("AT\r\n");
  }
}

Never use lock() or WITH_LOCK() within a SINGLE_THREADED_BLOCK() as deadlock can occur.