E16V3 - No reply if command issued just after another command to another device on th

[ldebacker]

Hello,

I have 2 E16V3 installed as 2 different slaves on the same modbus.

When I send a command to each in isolation, I  receive a response within a few milli-seconds from the E16V3.

But when I send a command to the second E16V3 immediately after successful response from the first one, then I never receive the response from the second device.

It seems that the second E16V3 is puzzled by the activity on the bus that is not intended to himself.

I have to retry the command to the second E16V3, or wait (20 miliseconds for example) before sending the command to the second E16V3

I can help troubleshooting further if needed.

BRs,

Laurent

[admin]

it's normal. after sent first command, need wait delay time to send second command.
the delay time according to RS485 baud rate. such as if you use 9600bps or 19200bps, must need wait >20ms.

[ldebacker]

it's normal. after sent first command, need wait delay time to send second command.
the delay time according to RS485 baud rate. such as if you use 9600bps or 19200bps, must need wait >20ms.

Actually, this is first command sent to the E16V3 device which poses problem. 

The issue is that the E16V3 does not answer to the command ...
... if there was, shortly before, activity on the bus for another device (a command was sent before to another device, and that the E16V3 should not be concerned about it).

so, in my opinion, this is not normal. 

The RS485 standard specifies a guard time (inter-frame delay) between the reception of the response and the next command of 1.75ms.

This is respected in my case and only the E16V3 has issues with this (it does not cause any issue for other devices on the same RS485 bus).

[admin]

can you take photo of your RS485 debug tool, i want to see all commands how send and received.

[ldebacker]

can you take photo of your RS485 debug tool, i want to see all commands how send and received.

I made further deep testing with 2 different RS485 adapters:
1. HW-519 (TTL <=> RS485) => The problem appears. I need to put at least 2ms delay between the response from the first device before sending to the E16. Otherwise, the E16 would not respond.
2. JZK adaptor (USB <=> RS485) : everything is fine, no issue , no need for an additional grace period

From the timings I see on my debug output, the pymodbus library doesn't automatically respect the 1.75 ms grace period.

So, I think the Kincony E16V3 is fine !
Thanks for the help.

So, the lessons learned:
1. Some RS485 adaptors are better than others
2. Manage the grace period yourself in the code

[admin]

ok, good.