💬 Building a wired RS485 sensor network

[gohan]

@Reza
not yet, but I am getting the parts to make a wired rs485 network of 4 nodes + gateway. About the NACK error it should be handled by the library and retransmit the lost packet.

[pjr]

Currently there is no "hw" ack functionlity like the radio has.
You can check out the rs485 transmit code from here.

But you can of course use the ack functionality between controller software and node to make sure message will get to destination.

[Reza]

@gohan now my sensors lib how many send packet if first is lost ? how more this ?
i want after send command Turn on light Certainly

[Reza]

i am tired for test and trying to configure wiring network with RS485. this is strange :angry:
i build a gateway and a relay with rs485 . for test i now use 2raspberry pi and 1orangepi and a laptop ! every time disconnect gateway from one and connect to other one ( with out other change for example sketch and wiring and etc. just change controller) some time this is very good work on laptop. some time good work on orange and some time good on raspbrrey pis !! some time same first command has sent(LED on gateway and on node just one blink. some time LEDs 2 blink and turn on later)
i am using 15cm wire between 2nodes! when change to some meter so dont work never...
so there is not any one that understand what is reason this issue !!!

i am ready and i have devices and madules. so any body that think can solve this , told me so i test on my devices and feedback.

[pjr]

@Reza have you tried to use terminating resistors?

And perhaps it could be good to try 1k pull-up and pull-downs at the gateway end. The left diagram:

With these two tricks I got my setup stable.

And a little tweak to transport class could help also..

[Reza]

@pjr
i use 120 ohm in terminate before. but now i use 1k for pull-up and down.but this is effectless.
please wait until i read this topic (rs485 stress test) and do it and feedback here . thank you

[Reza]

@pjr thank you for help , i read that topic hardly :) because i am weak in english.
What I understand , this problem is about collision , command and ack ! and related to transport rs485 and other friends trying to solve this ! is this true ?now , a rs485 network is not complete and Ideal and stable in mysensors.
i think all problem is related to collision in short wire and long wire. in many short wire i have not problem(between two nodes). in short wire gateway detect node and connect but many command are failed . in long wire gateway can not detect node and can not connect never.

[kimot]

@Reza
Original RS485 library was written so, that multiple SOH characters is sended on start of package.
In Mysensors library it is only one times and it can be problem for synchronization and arbitration.

Try in MyTransportRS485.cpp in function "transportSend" change line 274 from

for(byte w=0; w<1; w++) {

to

for(byte w=0; w<3; w++) {

[Reza]

@kimot said in 💬 Building a wired RS485 sensor network:

for(byte w=0; w<1;

thank you i will test this and again feedback here

[Reza]

@kimot this is good. i am testing . in the first test ((just for 2 node: gateway and one relay)) i see this is work well with 15cm wire. other test with 1meter and 5 meter work well.for 30 meter (CAT6) with 120 ohm resistor (first and end bus) dont work :) without resistor work with 15-20% error ( dont receive or send command and ack)
but i think this is good for 2 nodes and short distance and for more nodes and distance increase % errors. is this true ?

[Reza]

@kimot also do you have idea for improve wireless transport(nrf24)?
because for wireless also i have 50% error for commands.

[pjr]

Will the result change if you add more sync(SOH) chars?

[Reza]

@pjr i dont know what is this "for(byte w=0; w<3; w++)" because i am beginner but i see after change this , my network work better. very better. but no perfect

[kimot]

@Reza
This code makes, that your node sends three SOH bytes on beginning of message instead of only one SOH.

[kimot]

@Reza
Sorry, I do not know.
I am not using radio now (but RS485 too not).
I only look to code and try some RS485 library things,
but only two nodes connected through serial lines.
I am trying understand like MySensors code works to write my own library for CAN bus.

https://forum.mysensors.org/topic/5327/can-bus-transport-implementation-for-mys/17

[Reza]

@kimot thank you for help :pray:

[kimot]

@Reza
Like someone writes here, your module maybe includes all needed resistors for the bus on PCB.

http://yourduino.com/sunshop//index.php?l=product_detail&p=323

For two nodes it ok and you must not connect any terminating resistors.
For three and more, you must remove this resistors from PCB exclude those nodes, which are on the ends of bus.
Maybe you can divide your "big" problem to several "small" problems.
RS485 is tested bus and MUST work even on long cables.
It must be problem with electricity circuit or software.
Maybe software switchs direction pin to receiving mode early and not all data are send on the bus.
In MyTransportRS485.cpp maybe it is wrong .
It is "hard coded" for crystal 20MHz and bus speed 9600 bd. Try put your values.
//
_dev.flush();
delayMicroseconds((20000000UL/9600)+1);
//

Try examples from AltSoftSerial library with different lengths of cables and do not forgot handle your DE pin.
https://github.com/PaulStoffregen/AltSoftSerial

Or connect your two nodes only through serial wires and check functionality of your code without rs485 converters.

[Reza]

@kimot how remove resistors from PCB ? :O there is resistor onboard? so for first and end dont need connect external resistor ? in other means i must for example for 10 nodes , any change in node 1 and 10 ! and remove resistor for node 2 - 9 with soldering?
i test with some hardware. for 30 meter cable i dont use sheild cable. this is without sheild? may be problem for 30 meter is related to this ! is this true ?
i dont change any things in mytransport rs485 just W<3. also sketch is from site
im my transport is:
_dev.flush();
delayMicroseconds((20000000UL/9600)+1);

your last experience how many nodes you use ? with how much wire? and how % error for send and receive you have?

[scalz]

@Reza

I agree regarding your rs485 network you may need to adjust resistors. But i've not this setup, even if i would like to try it!

about removing smd resistor..if you have a solder iron, a simple trick :
Let's assume you want to push and remove your resistor to the right..

1. Add a blob of solder to the right pad (take a magnifier if you're not confident or smd is too small)
2. Heat well this pad. Not like hell, lol, but enough so solder will still be melted, for,
3. Then quickly move to the left pad, heat it, and push the resistor to the right for removing it.

Be careful with others parts around of course ;)

I hope it's clear :)

[Reza]

@scalz This is an exciting job :)
thank you
i hope it is clear too :)