Thanks for the clarification. Do you have any sense for how much latency might be involved using a serial command? I was trying to envision how to use the system as a lower cost, single-channel scope but a consistent trigger is essential. The red pitaya platform has a setting where the user can simply "listen" for the data and the transfer is initiated on receipt of a trigger on the board.
In the absence of that functionality, one approach might be to use a second microcontroller that can spit out the "t" and "*" characters upon an external trigger. Are there any future plans for expanded functionality to be added?