Specification for Format and Definition of Tilt Angle Query & Feedback Commands of Pelco_D Pan-Tilt Protocol

● Tilt Angle Query Command for Pan Tilt

Command Format:  FF 01 00 53 00 00 54

Description: When this command is sent to the pan-tilt, the unit shall return its current tilt position   command upon receipt of valid command.

● Tilt Angle Data Return Command

Command Format: FF 01 00 5B TMSB TLSB SUM

TMSB and TLSB are hexadecimal values; SUM is the least significant byte derived from the sum of the five bytes excluding the leading 0xFF.

Description: After the pan-tilt receives a valid tilt query command, it sends back a feedback command   containing tilt position information.

● Steps to calculate the tilt angle of the pan-tilt are as follows:

A. Convert the hexadecimal values of TMSB and TLSB into decimal numbers.

B. Calculate: Tdata = TMSB × 256 + TLSB to get the computed result.

C. Compare the magnitude of Tdata1 against 18000.

If Tdata1 is greater than 18000, Tdata2 = 36000  Tdata1;

If Tdata1 is less than 18000, Tdata2 = Tdata1.

C. Calculate actual tilt angle: Tangle=Tdata2÷100.

The calculated Tangle is the real absolute vertical tilt position value of the pan-tilt.

Example 1:

After sending the command FF 01 00 53 00 00 54 to the pan-tilt,

the pan-tilt responds with data-containing command  FF 01 00 5B 8A 63 49.

A、TMSB = 0x8A  TLSB = 0x63 convert to decimal values: TMSB = 138  TLSB = 99；

B、Tdata1 = TMSB *256 + TLSB = 138*256+99 = 35427；

C. Since Tdata1 > 18000, Tdata2 = 36000 Tdata1 = 36000  35427 = 573.

D、Tangle = Tdata2÷100 = 5.73°。 i.e., the current actual absolute vertical tilt position of the pan-tilt is 5.73°

Example 2:

After sending the command FF 01 00 53 00 00 54 to the pan-tilt,

the pan-tilt responds with data-containing command  FF 01 00 5B 00 64 C0

A、TMSB = 0x00  TLSB = 0x64  convert to decimal values: TMSB = 0  TLSB = 100；

B、Tdata1 = TMSB *256 + TLSB = 0*256+100 = 100

C、Since Tdata1 < 18000, Tdata2 = Tdata1 = 100.

D、Tangle = Tdata2÷100 = -1.00°。i.e., the current actual absolute vertical tilt position of the pan-tilt is -1.00°。