with older grandson (number of years ago) did some scratch etc and used the picoboard. was fun and interesting. younger grandson is doing some of the same now. this has re-awakened a question I had the first time around. is there a document that describes the serial protocol used by the rasp pi or pc versions of Scratch to talk to the picoboard? Or is it go to github and “use the source Luke, use the source”. Spent enough time in the employed days sussing out other folks’ c code that I’d rather start by knowing what they thought they were implementing before sorting out what they really implemented. 
Thanks
Here are some resources https://learn.sparkfun.com/tutorials/us … cratch/all but I cannot find anything that describes your mentioned serial protocol. You may ask your question here too: https://forum.makeblock.com/t/picoboard-drivers/3736