Thanks Piotr, the app works. I've done some tests on my PF train and have some observations:
1. On/off mode has about 0,5 second lag. I'm not sure whether it's due to the train motor, because in train mode motor starts immediately.
2. Train mode - first tap on +/- after STOP has no effect. There is no problem when going from forwards to backwards (1, 0, -1).
I hope it will help.