[solved] RS485 nodes stop sending data after some hours or days

[otto001]

@rejoe2 :
Thanks a lot!
I am having some unusual sketches (washing mashine monitoring, entry-system with fingerprint) where I am using self-written sketches with mysensors). Maybe I should wait. It is just annoying that the radio-stuff is not always working as it should. Indeed, esp with mqtt could be a solution too. But I do not know yet about the stability of esp-stuff :-(

Cheers,
Otto

[mick]

@pjr Is the network still operating ok? Curious to see if anyone has it fully operational as of yet.

[pjr]

@mick Its still in use. I had one bus freeze since last "update post".

The gateway did pull the line up to 190mV what seems to be enough to get traffic frozen. After "reboot" of the gateway it was still pulling the bus to 160mV so it must be some solder on wrong place and bad chinese pin headers or protoboards.. I have to rebuild the "motherboard" of the gateway..

[mick]

@pjr that sounds promising. My Serial gateway and one node ran for months with no problems. I’ve since added a node in between the two and that’s when I started having issues. Removing resistors on the middle node (terminating, pull-up and pulldown) and removing the pull-up and pull down on the end node seem to have fixed the issues for now however when I added an extra 20m to the cable run I started having issues again. I’de Love to get this network working 100% but I think a lot persistence and patience is needed! :)

[bakcsa]

Hints on RS-485 networks:

Termination resistors
You always need them. Termination resistors should be added to the nodes located at the ends of the line. The communication may works without them if the wire is short enough and/or the bit rate is low.

Pull up/down resistors a.k.a failsafe bias resistors
Why you need it is well explained here: https://electronics.stackexchange.com/a/284788/88486
When you need it: It depends on the RS485 transceiver IC. Most modern transceivers include these.

Common ground
Do you have a common ground between your transceivers? RS-485 is not a 2 wire network. Besides the A-B lines it requires ground.
See: http://store.chipkin.com/articles/rs485-rs485-cables-why-you-need-3-wires-for-2-two-wire-rs485
Schematics at http://www.analog.com/media/en/technical-documentation/application-notes/AN-960.pdf page 4.

Isolation
When you deal with long links, you have to take care of isolation.
Page 8 at http://www.analog.com/media/en/technical-documentation/application-notes/AN-960.pdf

[mick]

@rejoe2 - have you received the CAN modules yet? I’m very interested to see how they go

[rejoe2]

@mick Thanks for coming back to this topic, the stuff arrived already some weeks ago, but unfortunately I was busy with other parts, amongst them btw. a modification of the MySensors plugin for FHEM to get probems shown more easily. So finally some soldering work was on my list yesterday. So today there's the option to at least give some first impressions on that:

• Network is @57600 for the use of the TJA1050 modules.
• Soldered some adopter boards for direct replacement of the modified LC-Tech MAX487 modules, (crossed RX/TX as usual, there's no DE/RE, later also desoldered the 120 Ohm resistor)
• plugged it in Node_2's socket, and

WOW: It worked!

Tried a second one on the same node (module without the 121R): Also worked :smile:

So I continued and tried to teplace the transceiver at Node_3 with the tested (now resistorless) one:

NO LUCK!

Continued with the last transceiver in line holding the pullup/dow resistors: Also no luck :unamused:

So I decided to stop at that point to see how Node_2 will perform over night and meditate on the question why the behaviour on the other two nodes is different. Kept Node_1 and Node_4 not connected to the bus, so starting the experiment just with 3 nodes and the GW online.

This mornings's findings:

• (Node_2 hat at least once spontanously rebooted, but still was sending in data. I's rate this as some kind of partly success, but obviously the node needs to be reviewed, there most likely exists a problem not related to RS485.)
• (Node_5 was offline for whatever reason, no issues - as always - on Node_3)
• These transceivers can be used for MySensors@RS485
• They can be used in a mixed network together with normal transceivers
• BUT: (hypothesis) They may not be used in combination with altSoftSerial; Node_2 is HW-Serial, the other two still use software, so for them DE/RE might be essential (ISR?)

Additional remarks: I tried also a different power source for the 12V a couple of weeks ago - no difference (MAX487-only bus)
The GW was online during all of the time, it's uptime is 7 days by now (also SW-serial).

So I'll have to do some more testing on some of the topics and perhaps also build some more test nodes to avoid touching my "normal" bus too often - this seems to also cause additional trouble...

I'll come back when I know more, but again, this will take some time.

@bakcsa Thanks for this great summary!

[nofox]

I think the problem is not from the RS485 side, not from cabling etc. I have similar problems on my RS485 network, some nodes stop sending data for no reasons after some time (sometimes 2 days sometimes 4 weeks). I have changed from AltSoftSerial to HWSERIAL and its the same.. Maybe its about ENABLE PIN 2 ?? Anyone try to change this pin to other ??

[rejoe2]

@nofox Did you measure voltages on the bus?

Some additional info: I did some futher experiments using also MCP2551 as transceiver chip. As they are PIN-compatible to the TJA's, it was just a modification of the modules. I can confirme thess also to work.
General "restriction" is one has to use HW-serial. For me, that's ok, but if you want serial output for debugging, you also have to use altSoftSerial and use it for debug output.

This morning, I replaced the end-of-line module with a resistorless one (so also NO termination resistor is used on this side, only at the GW!).

At least, the Bus is working for some minutes now @56700 with just GW (MAX487) and one node for each of the tranceiver chips (MAX487, MCP2551 and TJA1050).

If that works more reliable, I'll switch all nodes to MCP2551 and lower the transmission rate, most likely to 19200 Baud. Will take again some time, but I'll keep you updated. For this I plan to use a STM32F103 as GW, if possible, I'll try to expose also the other two Serial Interfaces to the OS, so one could attach up to two other GW's (for other physical transport layers) to the STM using just one USB connection. But that's another project on another planet and if there's someone out there with more experience on how to do that: Thank's a lot...

[nofox]

Anyone know how to implement this https://github.com/MichaelJonker/HardwareSerialRS485/wiki to mysensors ? It can operate in multimaster mode and avoid collision issues.

[rejoe2]

Found this some days ago: https://github.com/mysensors/MySensors/pull/1142

Adding these changes to a 2.3.0-alfa base seem to make a big difference in reliability :grinning: .

So if there's other users having similar problems: please make also some testing of this patch.

You will get further updates and some more info on my recent setup, so far: Thanks a lot for all the ideas and hints to improve things!

[rejoe2]

As everything still seems to work as expected some futher remarks on my findings/hypothesis and todays setup:

General remark: As a lot of things have changed over time and some of my tests turned out to be contraproductive, it's hard to sort out THE root cause now. But as others had some issues with colliding messages too, I'd bet on that and really appreciate if the patch #1142 would find it's way to everyones codebase (@seeers seems to have some issues at github, can one of the mods help him out of that, please?) :grinning:.

Back to my setup:

• Nodes are powered now through a central 5V DC supply, only 3.3V conversion remains locally, GW through USB
• GND of central 5V is not connected to GW GND (in case of trouble, I'd add a "resistored" connection)
• All nodes use Hardware-Serial, Baudrate is @19200
• No debugging messages on nodes activated (if someone wants/needs it: swap debugging output to altsoftserial...)
• Transceiver used: MCP2551, most of them on modded TJA1050-Boards (don't forget to dissolder the R120) => no DE-Pins necessary
• Gateway is a Pro Micro
• Termination resistors: 2kOhm at the last node in line (CANhi->5V and CANlo->GND), 120Ohm (A-B) only at last node and GW

Remarks:

• My long-time GW was a regular MAX485/MAX487-Nano using AltSoftSerial. IMO this over time had been one of the most reliable components in my setup. Conclusion: Most likely this lib is NOT to blame for any trouble I ran into.
• Nevertheless hanging nodes with regular RS485 trasceivers caused problems to some extend. So I really like the CAN logic to switch the transceiver off when it's MC seems not to work properly to avoid infection of communication from other nodes. What I didn't test yet: Using CAN transceivers together with altSoftSerial. So expect some additional info on that later, as this might be helpful for debugging over USB as on any other node
• To some extend all of the transceivers seem to be able even to transmitt in case A-B voltage level is above the "critical value" - depends a little on the strength of the power source. So I'd see this just as some type of "most likely" indicator of a bus problem now.

Hope someone might find that summary helpful and once again:

Thanks a lot to all those people here and at FHEM-forum trying to help me out of that never ending mys(t)ery! :grin: :clap:

[rejoe2]

Thanks for helping @seeers at Github.

Still no communication issues to report, so just two additional remarks on the MCP2551 usage following some short tests on that:
They also seem to work at 9600 Baud and also using the MySensors standard (AltSoftSerial at PINs 8 and 9) is possible.

So for now, I'd recommend everybody thinking about new nodes to give this type of hardware a try. The only disadvantages may be

• the limitation in payload - but that seems not to be any practical issue in the use in an MySensors environment
• they might be more sensitive in crossing BusHigh and BusLow connection, so make sure all highs are on the same wire and also all lows :grin:

My favorites are kind of violet modules. Didn't come across them earlier, so I'd see all PINs on one side as a modest point for improvement. As there are also no resistors at all, just pads for soldering, there's also not the need of starting with desoldering unnecessary parts - just make sure, you have the right stuff to add :stuck_out_tongue_winking_eye: .

[rejoe2]

Everything's working like a charm now :grinning: , so thread is marked as [solved] now.
One more big "Thank you" to everybody helping to get this finally done :confetti_ball: :clap: !

In addition a picture of my Node 2 - the one I did the most rework over time until now also showing the violet MCP2551 module mentionned above.