Raspberry Pi and Micro Serial Servo Controller

I have an issue with connecting my Micro Serial Servo Controller.
When I send bytes 0x80, 0x01, 0x04, 0x0, 1000 & 0x7F, 1000 >> 7 & 0x7F nothing is happen with servo. I can see that green led is blinking slightly when I send these bytes but servo doesn’t move.
com_port is /dev/ttyAMA0 and baud rate 115200 (tried also 38400 - same result)

The wires connected this way:
TXD->OUT
RXD->SIN

Does anybody see what I missed?

Hello.

I am sorry you are having trouble connecting to that controller. In general, in order to communicate over serial between those devices, TXD from the Raspberry Pi should connect to SIN, RXD should connect to OUT, and the two should share a common ground. However, since the RPi GPIO pins are not 5V tolerant, you should use a level shifter like this to avoid damaging those pins. Also, without that kind of device, the servo controller might not recognize some of the signals from RPi.

-Jon