LeveLine
®
Instruction Manual
10401-01026 Rev D
6.4. SDI-12 Data Communication Protocol
SDI-12 is a standard for interfacing data recorders with microprocessor-based sensors.
SDI-12 stands for serial/digital interface at 1200 baud. The following sections describe the
protocol for communications between the LeveLine
®
Probes and SDI-12 data recorders
complying with Version 1.3 of the SDI-12 standard.
6.5. SDI-12 Data Packet Formats
The LeveLine
®
responds to commands sent to it by an SDI-12 data recorder. Command
packets should have the format:
<a><command-data>!
where:
•
<a> is the LeveLine's device address (valid values are ASCII “0”-“9”, “A”-“Z”, and
“a”-“z”) or the wild card address character “?”.
•
<command-data> is a string of zero or more command dependent data characters
(values in the range 0x20-0x7E, excluding 0x21 (ASCII “!”)).
•
the packet is terminated by 0x21 (ASCII “!”).
Each command sent to the LeveLine
®
must be preceded by a break frame (12mS high) to
wake the LeveLine
®
up.
Response packets have the format:
<a><response-data>[<crc>]<CR><LF>
where:
•
<a> is the LeveLine's device address character.
•
<response-data> is a string of zero or more command dependent data characters
(values in the range 0x20-0x7E).
•
<crc>, when present, is a string of 3 characters encoding the cyclic redundancy
check of the response data (1
st
character in the range 0x40-0x4F, 2
nd
& 3
rd
characters in the range 0x40-0x7F).
•
the packet is terminated by a carriage return followed by a line feed.
The formats of the individual command/response packets that the LeveLine
®
supports are
described in the following subsections.
6.5.1. Acknowledge Active
This command allows the data recorder to check that the LeveLine
®
is present on the SDI-
12 bus.
Command Response
<a>!
<a><CR><LF>
© 2019 Aquaread
®
Ltd.
www.aquaread.com
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