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RX and TX control port and com port

furban May 21, 2019 06:07 PM

I am reposting the inquiry (below) from a user named Chris- I have the same question and his inquiry was not answered fully but a solution was proposed.  My question is whether it is possible, as he suggests to use the TX side of a com port as a control port for another sensor if only the RX side is being used by the program (in my case for a digital sensor communication).  If not, would it be possible to use serialopen and serialclose commands within the program for different time amounts/slots to turn the serial communications option of the given com port off and on so it could be used as a control port while serial communications are closed?

Oct 18, 2010 05:15 PM

Is it possible to issue a serial open command that only activates the Rx line of a com port (e.g. C2 for Com1) on a CR1000? I'd like to use the control port on the Tx line (C1) of that com port to control another sensor. I need to open the serial port for the duration of the program, but will never use the Tx line on that port. I would love to utilize that control port for other activities. Com ports and control ports are becoming precious.


smile May 22, 2019 01:14 AM


I tried time for a similar situation and I believe there is no hope. If in the program a port is assigned as serial, it becomes impossible to make another use of it.

However you can try and see if CRbasic makes you compile.

Regarding the precious ports, keep in mind that there are CS devices that increase the serials coms or digital I / O ports without spending a lot of money.


furban May 22, 2019 08:25 AM

What devices does Campbell provide that would allow expansion for serial communications to more than the 4 com ports?  I am utilizing the main rs232 for telemetry.  I see the modules that allow for expansion of control ports but those actually use three C1, C2 and C3 control ports, thus eliminating the use of Com1 and Com2 for serial communications.  I am hopeful that there is a programming solution for this.   Currently we use a CR1000 for 4 serial communication sensors and a separate cr300 for our sensors that require another 2 contol ports.

AMK May 22, 2019 08:43 AM

You could add a network module and run a tcp/ip radio to free up your rs232 port. 

Vim May 22, 2019 09:41 AM

In your application, is there a restriction on using a SDM-SIO1A or SDM-SIO4A in conjunction with other SDM module to expand the number of ports?

furban May 22, 2019 11:57 AM

I dont think there is a restriction.  However, it would be good to be able to do this with just one CR1000.  We currently accomplish it with two loggers, one CR1000 that reads 4 eosGP sensors on the 4 RX lines of the com ports and one CR300 that reads 5 CS655 soil moisture sensors and one CS100 pressure sensor.   The CR300 is about $650 and the SDM-SIO4A is about $600 so what would we gain there other than one data stream?

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