Comet system forum

ermodillo · 10-10-2014 19:26:23

Hello,

I wrote a test program to communicate with a T7310 sensor. I use Ubuntu 12.04 and the open source libmodbus library.
The program simply connects to the sensor, retrieves a few data and then disconnects.

The program works perfectly with a T7310Z sensor, but with the T7310 sensor, I consistently get a timeout response. Digging with the debugger, I can see the ModBus communication fails at the POSIX select function described here:

http://pubs.opengroup.org/onlinepubs/96 … elect.html

Using an oscilloscope, I can see that the sensor received the "send 4 bytes" ModBus message from the PC and tries to send a reply after 10ms (I don't know the content of the reply though, I believe it's an aknowledgement or maybe a timeout message ?).
So what difference between the two devices is the source of this discrepancy ?

Thnk you for your help.

Last edited by ermodillo (10-10-2014 19:28:04)

PetrS · 13-10-2014 07:55:22

Hello,
the device of T7310 and T7310Z uses usually the same firmware, writing of device serial numbers can confirm it. Which powering do you use, from RS232 com port or external power supply? Does it communicate with TSensor software using? Free to download at http://www.cometsystem.com/userfiles/fi … .1.6.0.exe

ermodillo · 13-10-2014 11:28:21

Hello,

Indeed, the sensor doesn't work correctly with Tsensor: It does start and switches several time between the LCD full of gibberish and the actual temperature.
Finally, the software shows "Sensor connection failed!"

The powering is through RS232. I use a ATEN RS-232->USB bridge connector to connect the device to a USB 2.0 port.

I've tried with another sample of the T7310 and everything is fine.

Last edited by ermodillo (13-10-2014 11:49:37)

PetrS · 13-10-2014 12:31:20

The device is still restarting. It can happens for several reasons:
1) Insufficient power from serial port
2) Wrong communication parameter setting
3) Device HW issue

1) Check both DTR and RTS wires correctly connected to the device terminals. If so, try disconnect DTR and RTS wires and use external power supply (see users manual at http://www.cometsystem.com/userfiles/fi … 3_4_10.pdf page 5). If it works right now, probably the power from DTR and RTS signals of RS232 port is not sufficient (not specified into converter datasheet). Try to measure current consumption now, small difference between devices can be done by component tolerance.

2) If the device have wrong communication setting, TSensor tryies to start communication, if is not successfuly, then close serial port and switch off powering too. If it is possible, try to open serial port by SW only and see, if LCD shows correct measuring for longer time (more than 20 s) or try external power supply too. If power is right and communication parameters are right too, it should be communicating with TSensor SW.

3) I don't know if new or older device used by you for testing, may be corrupted. If new one, then it should be right.

Comet system forum

Temperature, Humdity,

Pressure Transmitters

and Data Loggers

#1 10-10-2014 19:26:23

Comet T7310 blocked on select

#2 13-10-2014 07:55:22

Re: Comet T7310 blocked on select

#3 13-10-2014 11:28:21

Re: Comet T7310 blocked on select

#4 13-10-2014 12:31:20

Re: Comet T7310 blocked on select

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