Hi!
Don't know if this info is still relevant for you but anyway :)
I suppose that you've read guide from there https://www.livetodai.com/t/diy-usb-greddy-blue-emanage-data-cable/519 and used USB-TTL converter YP-01 like this
https://i.ytimg.com/vi/IDM3MOWAcl0/hqdefault.jpg
This converter has...