Modbus Only Writes Zeros

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17 Jul 2020 23:29 #174977 by billnixon
I am trying to learn to use Classicladder's modbus. I am receiving the modbus communication on a slave simulator. When I start LinuxCNC, classicladder opens first and begins to communicate with the slave, but it only writes zeros. I tried assigning values to %QW1, but it still only writes a zero. I tried connecting a switch to an input, %I1, in hal, and then connect %I1 to %Q1 in classic ladder, then write %Q1 to a coil with modbus, but pressing the switch doesn't affect what modbus writes.

Here are some more potential clues:

My LinuxCNC gui does not open until I close classicladder. Once I do, the modbus communication stops.

If I open classicladder from the gui's menu, there is still no modbus communication, but the ladder rungs turn pink when I depress the switch I mentioned above. (The rungs do not turn pink when classicladder opens by itself before my LinuxCNC gui opens.)

If I open my gui while hiding the classicladder gui with --nogui, there is no modbus communication.

I'm not seeing any errors.

I am running version 2.8.0~pre1 with a qtpyvcp gui on Linux Mint 19.2 Cinnamon.

I attached my ladder file and my custom hal file
Attachments:

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18 Jul 2020 00:37 - 18 Jul 2020 00:37 #174989 by cmorley
Replied by cmorley on topic Modbus Only Writes Zeros
The w is lowercase should be uppercase:
loadusr -W classicladder --modmaster atc.clp

Lowercase means wait till the program ends, upper means wait till ready and continue.
Last edit: 18 Jul 2020 00:37 by cmorley.

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18 Jul 2020 01:11 #174990 by billnixon
Replied by billnixon on topic Modbus Only Writes Zeros
Thank you so much! That fixed it!

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18 Jul 2020 07:04 #175021 by cmorley
Replied by cmorley on topic Modbus Only Writes Zeros
Excellent. It's unfortunate that we didn't chose a different letter rather then case for this behavior - caught me a few times too.

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