Mesa modbus and pktUart

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06 Sep 2023 13:48 - 06 Sep 2023 13:49 #280102 by PCW
Replied by PCW on topic Mesa modbus and pktUart
1. That's active high TXEN (high when transmitting as expected)
2. The middle picture ( A,B )  doesn't seem to show any data
( if its at the same time per division as the other plots )
in fact it looks like the TXEN signal
Last edit: 06 Sep 2023 13:49 by PCW.

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06 Sep 2023 13:52 #280104 by Donno
Replied by Donno on topic Mesa modbus and pktUart
If i zoom time in to 10ms per grid line(I think) :

 
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06 Sep 2023 14:07 - 06 Sep 2023 14:08 #280105 by Donno
Replied by Donno on topic Mesa modbus and pktUart
I am using linuxCNC 2.9pre on raspberry i build latetest build and copied hostmot2.so and hm2_eth.so to make pktuart to work, could that cause problems ?
Last edit: 06 Sep 2023 14:08 by Donno.

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06 Sep 2023 15:00 - 06 Sep 2023 15:07 #280109 by PCW
Replied by PCW on topic Mesa modbus and pktUart
I would say there are still hardware issues
(idle line state is undefined)

 A must be high and B low when no one is driving the RS-485 bus
That's the reason for the 620 Ohm pullup on A and 620 Ohm pulldown on B
 
Last edit: 06 Sep 2023 15:07 by PCW.

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06 Sep 2023 16:16 #280116 by Donno
Replied by Donno on topic Mesa modbus and pktUart
I have rebuild circuit again using LTC485 ic :

 

Red is A and Yellow B. 1volt respectivly and 50ms :

 
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06 Sep 2023 16:24 #280117 by Donno
Replied by Donno on topic Mesa modbus and pktUart
TXen (Yellow) and TX(Red)

 

RX(Yellow) and TX(Red)

 

 

Does the circuit look right now ?
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06 Sep 2023 16:50 #280119 by PCW
Replied by PCW on topic Mesa modbus and pktUart
Yes the circuit looks correct now

(I would remove the 120 ohm resistor if still there to get better idle levels)

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06 Sep 2023 16:57 #280120 by Donno
Replied by Donno on topic Mesa modbus and pktUart
Removing the 120ohm gives a big voltage difference A(Red) and B(Yellow)

 

Still no joy with linuxcnc.
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06 Sep 2023 17:08 #280121 by PCW
Replied by PCW on topic Mesa modbus and pktUart
OK well at least now the hardware is correct so if the VFD is
not responding its likely something in the commands or serial 
protocol that the VFD doesn't like. 

Are you sure modbus is enabled on the VFD?

Have you tried different parity options?
(parity is not of much use since the packets have a 16 bit checksum)

If you set the mesa_modbus debug option to 3  you can see what is sent
to verify that it makes sense relative to what the VFD expects

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06 Sep 2023 17:37 - 06 Sep 2023 17:38 #280124 by Donno
Replied by Donno on topic Mesa modbus and pktUart
This is the settings i use with usb to rs485 dongle to connect to Servo Driver :

 

Everything working as expected.

 

I plug modbus back into ltc458 reset everything and tried different data format  I am getting hight time and tmax values ?

 

I think debug only works if the fault pin is false ?


 
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Last edit: 06 Sep 2023 17:38 by Donno. Reason: spelling

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