Useful SDI commands
Resetting the address by software (some sensors) is normally done by sending the aAb!
command. (a A b !, where a is the current address of the sensor you want to change and b
is the address you want to change to, e.g. 0A5! changes the address of sensor 0 to address
5.)
Another useful SDI-12 command is the aI! (where a is the address of the sensor, e.g. 3I!
for sensor at address 3) command. 4I! will return an identification string from the sensor
at address 4 which includes the SDI version number, vendor's name, sensor model
number, sensor version number, and serial number. This is a quick way to see if the
sensor is responding properly.
A way to verify data collection (manual data collection) is to issue the aM! command.
For example 7M! would collect data from the sensor at address 7. The sensor will
respond with a 5-digit code -- the first digit is the address, the next 3 digits are the
required time for measurement in seconds, and the last digit is the number of data values
returned. Wait for the number of seconds. Then issue the aD0! (address, D, zero, !) the
sensor should respond with one or more data values. You may issue further aD1! … aDn!
till you get all of the data.
If the SDI sensor is version 1.3 (which can be found out by sending the ?I! command; the
version is returned as the second and third characters of the response), then make sure to
use the CRC measurement commands. These commands work just like normal
measurement commands, except that they use an error checking mechanism that
minimizes errors. So, instead of 0M!, use 0MC!. Instead of 0M1!, use 0MC1!. This will
ensure reliable SDI communication.
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