What is the data rate of the signal?
Actually 38400 bps.
How long is each event?
That depends on the definition of an event.
A bit has got the length of 25 ns, a byte has got 250 ns an a complete telegram varies between 2 and 200 ms.
How many events do you want to capture?
As much as possible. While PicoScope provides up to 1000 wafveform buffers also up to 1000 telegrams if possible.
What is the time between events?
The time between the telegrams is approx. 2 to 5 ms. I set the trigger to Interval trigger, rising edge 500 ns (according to the baud rate 2 bytes long) and it works very well (triggering on the start bit of the first byte of a frame). As stop condition i think level dropout will be sufficient.