Using Commands and Logs
Chapter 4
EuroPak-15a Receiver User Manual Rev 5
37
3. The CRC is a 32-bit cyclic redundancy check performed on all data including the header. See
for the CRC algorithm.
4. The header is in the format shown in
.
Table 7: Binary Message Header Structure
Byte
Hex
Decimal
First
AA
170
Second
44
68
Third
12
18
Field
Field
Name
Field
Type
Description
Binary
Bytes
Binary
Offset
Ignored
on Input
1
sync
Char
Hexadecimal 0xAA
1
0
N
2
sync
Char
Hexadecimal 0x44
1
1
N
3
sync
Char
Hexadecimal 0x12
1
2
N
4
header
length
UChar
Length of the header
1
3
N
5
message
ID
UShort
Message ID. The message IDs for logs are given in
.
2
4
N
6
message
type
Char
Message type indicator, as explained in
.
1
6
N
7
port
address
Char
The port from which the log was generated.
See
1
7
N
8
message
length
UShort
The length in bytes of the body of the message. This
does not include the header nor the CRC.
2
8
N
9
sequence
UShort
For multiple related logs. A number that counts
down from N-1 to 0 where N is the number of
related logs and 0 means it is the last one of the set.
Most logs only come out one at a time in which case
this number is 0.
2
10
N
10
idle time
Char
The percentage of time that the processor is idle in
the last second. Take the time (0-200) and divide by
two to give the percentage of time (0-100%).
1
12
Y
11
time status Enum
The quality of the GPS time, as described in
1
a
13
N
b
12
week
UShort
GPS week number
2
14
N
b
13
milli-
seconds
GPSec
Milliseconds from the beginning of the GPS week
4
16
N
b
14
receiver
status
ULong
32 bits representing the status of various hardware
and firmware components of the receiver. This
number is described in
.
4
20
Y
15
Reserved
UShort
Reserved for internal use
2
24
Y
16
UShort
2
26
Y
a. This ENUM is not 4 bytes long but, as indicated in the table, is only 1 byte.
b. These time fields are ignored if Field #11, Time Status, is invalid. In this case the current receiver time is used. The
recommended values for the three time fields are 0, 0, 0.
