RS-485 with 7i76
- tensaiteki
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28 Jun 2012 23:34 - 28 Jun 2012 23:35 #21445
by tensaiteki
RS-485 with 7i76 was created by tensaiteki
Is it possible to control a single RS-485 with the RS-422 interface in the 7i76?
I would like to control a Hypertherm Powermax 85 (plasma cutter) that has a RS-485 (5-pin) interface.
I'd like to avoid having to buy a separate RS-485 board just to control a single device.
I would like to control a Hypertherm Powermax 85 (plasma cutter) that has a RS-485 (5-pin) interface.
I'd like to avoid having to buy a separate RS-485 board just to control a single device.
Last edit: 28 Jun 2012 23:35 by tensaiteki.
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- PCW
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29 Jun 2012 02:23 #21451
by PCW
Replied by PCW on topic Re:RS-485 with 7i76
Maybe, what is the protocol? There is UART support
in the master version of HostMot2
The expansion connector on the 7I76 is RS-422
(full duplex 4 wire = 1 differential pair in and out)
and will not support 2 wire 1/2 duplex physical interfaces
so that may also be an issue
in the master version of HostMot2
The expansion connector on the 7I76 is RS-422
(full duplex 4 wire = 1 differential pair in and out)
and will not support 2 wire 1/2 duplex physical interfaces
so that may also be an issue
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- tensaiteki
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29 Jun 2012 16:38 #21459
by tensaiteki
Replied by tensaiteki on topic Re:RS-485 with 7i76
Here is the serial communication spec sheet from Hypertherm: app.dumptruck.goldenfrog.com/p/3A2SuSfyEe
The protocol seems to be ModBus ASCII. I'm pretty sure the Hypertherm uses full duplex as the 5 pins on the connector are shown as TX+, TX-, RX+, RX-, and Gnd.
The protocol seems to be ModBus ASCII. I'm pretty sure the Hypertherm uses full duplex as the 5 pins on the connector are shown as TX+, TX-, RX+, RX-, and Gnd.
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29 Jun 2012 17:47 #21460
by PCW
Replied by PCW on topic Re:RS-485 with 7i76
Well it looks possible hardware wise, but its likely much easier to just use the userland modbus interface with a USB-485 adpater
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- tensaiteki
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29 Jun 2012 20:49 #21464
by tensaiteki
Replied by tensaiteki on topic Re:RS-485 with 7i76
How fast would a USB solution be?
One of the things I was hoping to do was be able to vary the cut current with the travel velocity, i.e. if the machine has to slow down to take a corner I want to lower the cut current until the machine can speed back up.
One of the things I was hoping to do was be able to vary the cut current with the travel velocity, i.e. if the machine has to slow down to take a corner I want to lower the cut current until the machine can speed back up.
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29 Jun 2012 21:03 #21465
by PCW
Replied by PCW on topic Re:RS-485 with 7i76
Well its in userland so theres no guaranteed response time my guess would be in the 10 to 100 mS regions mostly
does the plasma power source guarantee ~real time response to Modbus commands?
does the plasma power source guarantee ~real time response to Modbus commands?
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- dano87
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03 Jul 2012 11:09 #21520
by dano87
Replied by dano87 on topic Re:RS-485 with 7i76
tensaiteki wrote:
I agree with what PCW says.
Is it possible to control a single RS-485 with the RS-422 interface in the 7i76?
I would like to control a Hypertherm Powermax 85 ( plasma cutter ) that has a RS-485 (5-pin) interface.
I'd like to avoid having to buy a separate RS-485 board just to control a single device.
I agree with what PCW says.
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- andypugh
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04 Jul 2012 12:30 #21556
by andypugh
Replied by andypugh on topic Re:RS-485 with 7i76
tensaiteki wrote:
[quoteThe protocol seems to be ModBus ASCII. I'm pretty sure the Hypertherm uses full duplex as the 5 pins on the connector are shown as TX+, TX-, RX+, RX-, and Gnd.[/quote]
That looks like it could be quite an interesting driver to write. Do you have any feel for how many characters you would want to send every servo-thread?
The data 11 characters per register, and three registers every cycle. At 19200 baud and 11 bits per character that is a cycle time of around 20mS so the driver would have to be quite careful with buffering if running a realtime driver in the servo thread (1mS)
In practice you would presumably only send new data when the buffer was empty, and also only send changed data.
git.linuxcnc.org/gitweb?p=linuxcnc.git;a...b7f40eed0572cd497ac0
Is a simple skeleton driver for the Hostmot2 UART written in the "comp" component definition language. It would make a reasonable basis for a driver for your Hypertherm.
How are you at C coding?
Note that you would need a special firmware for the 5i25 with a UART in place of the usual SmartSerial module. (There are a number of us who can create firmwares, so this is not a major difficulty)
[quoteThe protocol seems to be ModBus ASCII. I'm pretty sure the Hypertherm uses full duplex as the 5 pins on the connector are shown as TX+, TX-, RX+, RX-, and Gnd.[/quote]
That looks like it could be quite an interesting driver to write. Do you have any feel for how many characters you would want to send every servo-thread?
The data 11 characters per register, and three registers every cycle. At 19200 baud and 11 bits per character that is a cycle time of around 20mS so the driver would have to be quite careful with buffering if running a realtime driver in the servo thread (1mS)
In practice you would presumably only send new data when the buffer was empty, and also only send changed data.
git.linuxcnc.org/gitweb?p=linuxcnc.git;a...b7f40eed0572cd497ac0
Is a simple skeleton driver for the Hostmot2 UART written in the "comp" component definition language. It would make a reasonable basis for a driver for your Hypertherm.
How are you at C coding?
Note that you would need a special firmware for the 5i25 with a UART in place of the usual SmartSerial module. (There are a number of us who can create firmwares, so this is not a major difficulty)
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