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

If i zoom time in to 10ms per grid line(I think) :

 

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 ?

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
 

I have rebuild circuit again using LTC485 ic :

 

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

 

TXen (Yellow) and TX(Red)

 

RX(Yellow) and TX(Red)

 

 

Does the circuit look right now ?

Yes the circuit looks correct now

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

Removing the 120ohm gives a big voltage difference A(Red) and B(Yellow)

 

Still no joy with linuxcnc.

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

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 ?