the the terminal / ASCII protocol. This means in particular: After one start character ({) of the framed
protocol has been received, the device switches to framed protocol mode and subsequently ignores every
input which is not packed in a valid protocol frame. To return to the terminal / ASCII protocol mode, switch
off the receiver and switch it on again.
The RS422 streaming interface is a unique feature of the sat-nms LBRX-1MT beacon receiver. The
interface reports the measured value in a compressed binary format at the full measurement rate of the
receiver (1000 values per second).
The RS422 streaming interface sends each level value as a 2-byte message at 38400 baud, no parity, one
stop bit. In this message, the beacon level is contained as a 14 bit unsigned integer value showing the
negative beacon level [dBm] in steps if 0.01 dB:
level [14-bit-integer] = - beacon-level [dBm] * 100
The 14 bit value coded this way is capable to represent levels in the range -163.83 .. 0.00 dBm. At the
interface, it gets coded into two bytes, each containing 7 bits of the value and one bit to mark the high / low
byte of the value.
1st Message Byte
bit-no
description
7 (msb) always 1, marks the 1st message byte
6
bit 13 (msb) of the level value
5
bit 12 of the level value
4
bit 11 of the level value
3
bit 10 of the level value
2
bit 9 of the level value
1
bit 8 of the level value
0 (lsb)
bit 7 of the level value
2nd Message Byte
bit-no
description
7 (msb) always 0, marks the 2nd message byte
6
bit 6 of the level value
5
bit 5 of the level value
4
bit 4 of the level value
3
bit 3 of the level value
2
bit 2 of the level value
1
bit 1 of the level value
0 (lsb)
bit 1 (lsb) of the level value
The following C-code example explains how to retrieve the level value from the binary data received from
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www.satnms.com
LBRX-1MT-UM-2002 Page 11/21
