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Hi everyone,
I've got a dilemma here--I'm trying to communicate with a Watlow F4 which is controlling an environmental chamber. The controller uses RTU and has an RS232 port. The manual states there should be no parity.
I've made an RS232 cable using 3 wires--straight through. I've also tried a null modem cable but have been informed that I should be using a straight-through cable.
I've tried Modbus Poll, Watlow's ModbusTest and Comm7, and found some MATLAB code (which would be ideal and my end goal to use). All of these have been confirmed to be outputting what appears to be a valid RS232 signal with an oscilloscope. However the F4 does not reply. (I've fashioned a little connector that allows the F4 to be hooked up while the Rx and Tx lines are being monitored by the scope) Not even an error message. I am under the impression that if a Modbus slave receives an invalid command it will report an error, am I wrong?
Answers to inevitable questions:
The baud rate matches (9600 but I have also tried 19200 on the slave and the program) Slave address is correct (1)
Comm port is correct (especially seeing as how the signal is getting to the controller)
I am trying to read from register 100, relative addressed, in which the current temperature of the chamber is stored
Here are the settings I am using to attempt "contact" with the timid controller:
-8 data bits (RTU standard, amirite?)
-no parity
-1 stop bit (I understand this defaults to 2 stop bits when there is no parity but I have been told this is what I should be using)
-Additionally, I have systematically tried every combination of 7 or 8 data bits, even/odd/no parity and 1 or 2 stop bits.
Anyway, I have been at this for over a week now without a single peep from the F4 and I am at a loss. I have talked to 4 different tech support guys from Watlow and Tenney (manuf. of the chamber) and stumped every one of them. One of my predecessors, who has since left the company has gotten it to work with Modbus Poll about a year ago. He said he was in a similar situation and he just had to "fix the port" to get it to respond. Well there are not a whole lot of options in Modbus Poll for me to mess around with. The only thing beyond the data bit/parity/stop bit options are DSR, CTS, RTS and Echo which I am not too familiar with but tried messing around with them to no avail.
I am new to Modbus and can't help but think: there is no way this 2-year-old $1000 controller stopped working over the course of a year of inactivity. I have GOT to be missing something, and hopefully someone more seasoned in Modbus can point out the obvious. If you have a suggestion that seems obvious, I'd love to hear it. If you have any other suggestion, same deal. I am really starting to resent the poor F4 and I would like to be able to cultivate some sort of relationship, I just need her to talk to me!
Thanks in advance for your help.
All the best,
Nate
I've got a dilemma here--I'm trying to communicate with a Watlow F4 which is controlling an environmental chamber. The controller uses RTU and has an RS232 port. The manual states there should be no parity.
I've made an RS232 cable using 3 wires--straight through. I've also tried a null modem cable but have been informed that I should be using a straight-through cable.
I've tried Modbus Poll, Watlow's ModbusTest and Comm7, and found some MATLAB code (which would be ideal and my end goal to use). All of these have been confirmed to be outputting what appears to be a valid RS232 signal with an oscilloscope. However the F4 does not reply. (I've fashioned a little connector that allows the F4 to be hooked up while the Rx and Tx lines are being monitored by the scope) Not even an error message. I am under the impression that if a Modbus slave receives an invalid command it will report an error, am I wrong?
Answers to inevitable questions:
The baud rate matches (9600 but I have also tried 19200 on the slave and the program) Slave address is correct (1)
Comm port is correct (especially seeing as how the signal is getting to the controller)
I am trying to read from register 100, relative addressed, in which the current temperature of the chamber is stored
Here are the settings I am using to attempt "contact" with the timid controller:
-8 data bits (RTU standard, amirite?)
-no parity
-1 stop bit (I understand this defaults to 2 stop bits when there is no parity but I have been told this is what I should be using)
-Additionally, I have systematically tried every combination of 7 or 8 data bits, even/odd/no parity and 1 or 2 stop bits.
Anyway, I have been at this for over a week now without a single peep from the F4 and I am at a loss. I have talked to 4 different tech support guys from Watlow and Tenney (manuf. of the chamber) and stumped every one of them. One of my predecessors, who has since left the company has gotten it to work with Modbus Poll about a year ago. He said he was in a similar situation and he just had to "fix the port" to get it to respond. Well there are not a whole lot of options in Modbus Poll for me to mess around with. The only thing beyond the data bit/parity/stop bit options are DSR, CTS, RTS and Echo which I am not too familiar with but tried messing around with them to no avail.
I am new to Modbus and can't help but think: there is no way this 2-year-old $1000 controller stopped working over the course of a year of inactivity. I have GOT to be missing something, and hopefully someone more seasoned in Modbus can point out the obvious. If you have a suggestion that seems obvious, I'd love to hear it. If you have any other suggestion, same deal. I am really starting to resent the poor F4 and I would like to be able to cultivate some sort of relationship, I just need her to talk to me!
Thanks in advance for your help.
All the best,
Nate