RS485/RS232/Serial transport class for mysensors.org

LeoDesigner

@tbowmo
Node will listen RS485 bus before it will try to transmit anything (just like Ethernet).
So other nodes will behave yourself :)
But we have another difficulty: standard bootloader know nothing about TX/RX (dePin) management. So, we need to modify it to be able correctly emulate Arduino upload process. Maybe a simple schematics with diode will work in that case.
I am still busy with other improvements.

TimO

@hek I've tested your code and can't get it working yet.

I've installed the gateway and a DHT22 sketch on two nanos and connected them directly via D8 and D9.

// Enable RS485 transport layer
#define MY_RS485

// Set RS485 baud rate to use
#define MY_RS485_BAUD_RATE 9600


#include <MySensor.h>
#include <DHT.h>  

#define INTERRUPT DIGITAL_INPUT_SENSOR-2 // Usually the interrupt = pin -2 (on uno/nano anyway)
#define CHILD_ID_HUM 0
#define CHILD_ID_TEMP 1
#define HUMIDITY_SENSOR_DIGITAL_PIN 3
#define RS485_DE_PIN 4
unsigned long SLEEP_TIME = 3000; // Sleep time between reads (in milliseconds)

// Initialize motion message
DHT dht;
boolean metric = true; 
MyMessage msgHum(CHILD_ID_HUM, V_HUM);
MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);

void setup()  
{  
  dht.setup(HUMIDITY_SENSOR_DIGITAL_PIN);
}

void presentation()  {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Humidity Sensor", "1.0");

  // Register all sensors to gw (they will be created as child devices)
  present(CHILD_ID_HUM, S_HUM);
  present(CHILD_ID_TEMP, S_TEMP);
}

void loop()     
{     
  float temperature = dht.getTemperature();
  if (isnan(temperature)) {
      Serial.println("Failed reading temperature from DHT");
  } else  {
    send(msgTemp.set(temperature, 1));
    Serial.print("T: ");
    Serial.println(temperature);
  }
  
  float humidity = dht.getHumidity();
  if (isnan(humidity)) {
      Serial.println("Failed reading humidity from DHT");
  } else {
      send(msgHum.set(humidity, 1));
      Serial.print("H: ");
      Serial.println(humidity);
  }
  // Sleep until interrupt comes in on motion sensor. Send update every two minute. 
  sleep(SLEEP_TIME);
}

The sketch is working fine according to serial output. But nothing is seen on the gateway.

So, to find out, where there is a problem, I connected my Programmer (mySmartUSB MK3) to D8/D9 of the sensor and I'm able to see that there is output but the chars are not readable so I tried different baudrates than 9600. That didn' help. What I can say is, that the output is generated every 3 seconds, so the ports are right.

To make sure I'm not doing something wrong with the programmer, I connected it to D0/D1 and switched baudrate to 115200 and it shows the serial output as expected.

Any idea where to look next?

TimO

So, I've tried to further invest the problem and there is something wrong with _dev.write() in transportSend(). It is too much C-Kungfu for me but there is something wrong with the conversion of data.

_dev.write("bla") looks good in terminal
_dev.write(to) throws trash in the terminal
Serial.println(to) looks good in terminal

Here is the output of the soft-serial:

#���X��z
               �Humidity Sensor��X
��
     �1.0�X��b�X��b�X
                                     ��*�������X
                                                     ��*�gfB�X
                                                                    ��*�������X
    ��*�gfB�X

Another thing:

The management of the DE-Pin is missing right?

hek

to is a uint_t...so I guess it could generate trash in the terminal when showing the low ASCII values. Guess you'd have to use some other program to view the bytes sent.

Yes, de-pin was stripped away. Would it be useful in your setup?

(thankful for your help out testing it... I need some more time before I can setup a test rig)

TimO

Holy crap ...
It was too obvious. :-(

Gateway can't work with this code:
https://github.com/mysensors/Arduino/blob/development/libraries/MySensors/examples/GatewaySerialRS485/GatewaySerialRS485.ino

#define MY_DEFAULT_ERR_LED_PIN 7  // Error led pin
#define MY_DEFAULT_RX_LED_PIN  8  // Receive led pin
#define MY_DEFAULT_TX_LED_PIN  9  // the PCB, on board LED

@hek: Your code works!

The de-pin is set to high if a node wants to send something, otherwise it is set to ground.
I'll try to add that code.

hek

@TimO

:blush: I Sorry.. should have changed those pin assignments of course... I'll push an update ASAP.

LeoDesigner

@hek
I am wondering why did you remove the code responsible for dePin management ?
It's not possible to use MAX485 boards without tx/rx management.

TimO

@LeoDesigner : yeah, you're right, that is needed.

But there seems to be another problem, I can't get the current development code to work. I've simply interconnected two Nanos at D8/D9. The gateway and the motion example come up fine according to serial output and the motion sensor definiatly sends something via AltSerial but the gateway doesn't seem to recognize it.

A simple test, where I pipe the input on hardware serial of one nano to AltSerial on the second nano and from there to hardware serial works just fine, so hardware and AltSerial is working.

Sender:

#include <AltSoftSerial.h>

AltSoftSerial altSerial;

void setup() {
  Serial.begin(115200);
  Serial.println("Demo begins");

  altSerial.begin(115200);

}

void loop() {
  char c;

  if (Serial.available()) {
    c = Serial.read();
    altSerial.print(c);
  }

}

Receiver:

#include <AltSoftSerial.h>

AltSoftSerial altSerial;

void setup() {
  Serial.begin(115200);
  Serial.println("Demo begins");

  altSerial.begin(115200);

}

void loop() {
  char c;

  if (altSerial.available()) {
    c = altSerial.read();
    Serial.print(c);
  }

}

hek

Added DE-pin management

https://github.com/mysensors/Arduino/pull/266

shabba

I am very interested in doing this as I have many sensors local to my gateway. I use domoticz and see from http://www.domoticz.com/forum/viewtopic.php?f=6&t=8018 that people are doing this. I was just wondering would this do as a USB adaptor? Seems very cheap :

http://www.aliexpress.com/item/1-pcs-USB-to-RS485-USB-485-Converter-Adapter-Support-Win7-XP-Vista-Linux-for-Mac/1684582905.html?spm=2114.031010208.3.1.hHoz94&ws_ab_test=searchweb201556_10_79_78_77_80_61,searchweb201644_0,searchweb201560_9

Also was looking at :
http://www.aliexpress.com/item/FREE-SHIPPING-5PCS-LOT-MAX485-module-RS485-module-TTL-turn-RS-485-module-MCU-development-accessories/1718665649.html

Appreciate any feedback.

Thanks.

MarkV

@LeoDesigner

I'm searching for a usb transport class, could i use this??

I'd like to connect my arduino (with sensors/actuators connected to it) to my rasberrypi through usb, without the wireless part, but still see them as mysensors sensors.

Is this possible or could someone make a transport class for it???

LeoDesigner

@MarkV
Regarding the USB to RS485 adapters:
I think they are using a some kind of serial to USB chip like CH340/341. So your RPi will be able to see RS485 bus as the regular serial port. It may work. It worth trying, you can always build an Ethernet GW later in other case.

@shabba
I am using exactly the same MAX485 modules. It is much more reliable media comparing to radio communication.

@hek
Thanks for adding DE pin management code.

scalz

hi.

I am not sure if it can be useful.. I have read this note recently, about rs485 powering chip (3.3v or 5v). And I found this interesting, for knowledge..
https://e2e.ti.com/support/interface/industrial_interface/f/142/t/93260
So what I understand here, and it makes sense, is that : even if some rs485 chips are able to be powered with 3.3v or 5v, if you want to power it with 3.3v, it can work of course with a 5v chip, but it is better to use a true 3.3v chip only. Because they are more sensitive to be rs485 compliant (better internal transistor).

Always good to know :smiley:

anti

@TimO I cloned the current development branch, and tried to use a modified motion sketch, and a gateway sketch, simply interconnecting two mini-pros with TTL serial : the same problem appears.

I can only see garbage sent on the AltSerial pins, so the gateway don't see the message.

Before I dig more and start debugging, did anybody made progress on that problem ?

TimO

@anti: I'm glad, I'm not the only one! :-)
I've tried to find the problem, but had no luck.

What is bugging me: it was working with a early version, before it was merged into development, but I don't see any changes.

I've not tested the latest / current version though.

andriej

Hi!

Glad to see 'wired' version of MySensor protocol coming.
One question - how long wires and how many sensors on one pair/multiple pairs will be supported?

I'm thinking about cabling for new home, which means many meters of cable to every sensor/door/actuator/ligth/meter etc.

In best scenario - one cat5e - one termination (sensor/node/etc.)
Currently I'm looking for a cabled version of protocol to support it and be 101% stable (no hiccups and freezes over the protocol), so I can rely on my home.

MySensors seems to be great to implement, but I'm worried about the signal... I was thinking about letting something around 12-24-30V thru one pair of Cat5 to power all nodes from one power-source (with backup batteries).

Or - are there any better alternatives for RS485, that doesn't need resistors, have no limitations of 32 devices etc?

LeoDesigner

@andriej
According to: https://en.wikipedia.org/wiki/RS-485
"It offers data transmission speeds of 35 Mbit/s up to 10 m and 100 kbit/s at 1200 m. "
also check this: https://www.maximintegrated.com/en/app-notes/index.mvp/id/367
You may design a bus with up to 256 nodes.
CAT5 is the best choice anyway for any type of communication (I mean you can run regular Ethernet on them too).
Check the video at the beginning of the post. It's a working example of two remote nodes connected only with one CAT5 cable over 50m. They are working at 115200 - however speed might be up to 1 Mbit/s.

andriej

@LeoDesigner but how would I connect all sensors in house and relays too?
SOme resistors needed? Star topology? Few gateways?

LeoDesigner

@andriej
The star topology could be a problem. However for low speed nodes this may work anyway.
You may need something like RS485 hub :) or a GW with many RS485 bus ports.
Or just a separate MAX485 board for each node. You need to test it.

anti

@TimO Well... it turns out that the garbage seen on the wire was not garbage, just the binary serial protocol. And the node was desperately attempting to find a parent, with no success.

FYI this is how I workaround it. But I did not feel like I could fix it for 100% sure.

The gateway ignored the broadcasts from the node. The following code in MyTransportRS485 triggered for probably wrong reasons (sender=0; nodeid=0;station=broadcast) :

               if ((_recSender == _nodeId) ||
                  (_recStation != _nodeId &&
                   _recStation != BROADCAST_ADDRESS)) {
                          _dev.print(" wrongid: ");

Since the gateway was not responding correctly to the node broadcasts, I solved the serial communication problem between node and gateway by defining a fixed node Id :

#define MY_NODE_ID 10

(ps: the MySensors version used was cloned from git today)

RS485/RS232/Serial transport class for mysensors.org

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