Programming Guide
Marathon MM Rev. D7 Jul 2017 67
10 Programming Guide
This section explains the sensor’s communication protocol. A protocol is the set of commands that
define all possible communications with the sensor. The commands are described along with their
associated ASCII command characters and related message format information. Use them when writing
custom programs for your applications or when communicating with your sensor with a terminal
program.
10.1 Serial Interface versus Control Panel
Since the sensor includes a control panel, the possibility exists for the user to make manual changes to
parameter settings. To resolve conflicts between manual parameter settings and settings by means of
the serial interface, the sensor observes the following rules:
Command precedence: the most recent parameter change is valid, whether originating from
control panel or the serial interface.
If a manual parameter change on the control panel is made, the sensor will transmit a
“notification” string to the host (e.g. a PC). Notification strings are suppressed in multidrop
mode.
10.2 Storing of Parameters
All sensor parameters, which are changed via the serial interface, are changed in the sensor internal
EEPROM memory. The EEPROM memory will retain all information after powering off the sensor.
10.3 Command Structure
After transmitting one command, it is obligatory to wait for the response from the sensor before sending
another. Make sure that a command sent was completely transmitted from the sender before the next
command can be sent.
10.3.1 Requesting a parameter (Poll Mode)
?E<CR> “?” is the command for “request”
“E” is the parameter requested
<CR> carriage return (0Dh) is closing the request
10.3.2 Setting a parameter (Poll Mode)
E=0.975<CR> “E” is the parameter to be set
“=” is the command for “set a parameter”
“0.975” is the value for the parameter
<CR> carriage return (0Dh) is closing the setting
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