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•
Example: ELD has previously issued a SeeLeveL Query Alarm Liquid
Level Message (0x07) to a SeeLevel device which does not support
alarms:
•
[0xFE][0xFE][0x24][0x0A][0x0F
SeeLeveL Liquid Level Report Message
•
Value: 0x10, 6 or 7 byte payload, depending on whether alarms are
supported
•
SeeLeveL transmits liquid level (4 bytes = unsigned int32), number of
digits to the right of the decimal (1 byte), optical error status (1 byte),
and alarm status (currently active = 0x01, not in alarm state = 0x00).
The alarm status field is optional and is not transmitted by a SeeLevel
device which does not support alarms. Optical error status: no light
= 0x00, low light level = 0x01, sunlight = 0x02, no error = 0x10. In
the event that the optical error status is NOT in error, the liquid level/
number of digits to the right of the decimal is ignored.
•
Example: liquid level = 1,083.1, no optical error, alarms not supported.
•
For the liquid level, the first 4 bytes of the payload represent the hex
value of the level, not the BCD value.
•
[0xFE][0xFE][0x24][0x0F][0x10][0x00][0x00][0x2A][0x4F][0x01][0x10]
[0xC9][0xFF][0xFF][0x2A]
Broadcast:
•
Done after every data reception (good or bad) or no signal timeout
for the 808P2 and 810PS2 gauges. Done after every 8 successful data
transmissions for the 806B/806Bi gauges.
•
Every 25 broadcasts (approximately 20 seconds) a handshake request
is sent to allow continued broadcasts.
•
On power up, if broadcasts are enabled, a handshake request is sent
to allow broadcasts.
•
Does NOT need a handshake to stop broadcasts.
•
If a handshake request is not correctly responded to, the broadcasts
are stopped.
•
The Begin and Stop Broadcast requests are not explicitly responded to,
the starting or stopping of the broadcast is the confirmation.
Page 12
][0x07][0x40][0xFF][0xFF][0x2A]
(SeeLeveL ->
ELD)
T-DL0301-A Manual
ELD requests needing handshake confirmation:
•
Start broadcast and Send liquid level
•
The handshake request is done every time one of these requests is
received. The handshake must be responded to within 500ms, or
else the response is considered invalid and an error message will be
sent from the SeeLeveL to the ELD for late responses.
Handshake format:
•
Request from ELD is received by SeeLeveL
•
SeeLeveL responds with handshake request
•
ELD sends handshake response
•
SeeLeveL sends reply to original ELD request if handshake response
is correct.
The alarms are not currently supported. In the future, if they are:
•
The content of Message 0x08 is alarm set point, high or low level
alarm, and current alarm status.
SeeLeveL Query of Handshake Frequency During Broadcast Message
(ELD ->
SeeLeveL)
•
Value:
0x2D
•
This asks for the handshake frequency, response is shown below.
•
[0xFE][0xFE][0x24][0x09][0x2D][0x56][0xFF][0xFF][0x2A]
Handshake Frequency During Broadcast Response
•
Value: 0x2E, 1 byte payload
•
The frequency can range from 1 to 126 broadcasts per handshake
request. The number is shown in hex from 0x02 to 0x7F (total number
of transmissions per handshake, including the handshake).
•
Message format, frequency is 20 (0x14):
•
[0xFE][0xFE][0x24][0x0A][0x2E][0x14][0x6C][0xFF][0xFF][0x2A]
T-DL0301-A Manual
(SeeLeveL ->
ELD)
Page 13
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