RS485/RS232/Serial transport class for mysensors.org

[TimO]

Woah, nice!! I've thought about doing the same but didn't find the time.
I will try to test, the RS485 are already lying on my desk.

[TheoL]

I have to wait before my Guests will leave, but this is something I'm interested in. Will check it in a week or two. I want to have a sensor that checks whenever I lay in my bed. I'd preffer to transfer this kind of details wired and not wireless ;)

[pjr]

Testing this will be next thing in my todo-list. Just ordered needed parts :)

[shabba]

I just started a thread on using sensors without a radio. So this really caught my attention. Would it be possible to modify it to use the USB Serial interface for arduinos that have it?

[LeoDesigner]

@shabba I am not quite understood what exactly you want to do with USB. You can use arduino nano without any problems at all.
All you have to do just to make sure to disconnect your RS485 bus from RX pin during the time when you will upload your sketch/firmware.
Also it is possible to use this class without any converters at all. See attached simple schematics on github page.
Regarding USB - you can attach an RS485-USB adapter to this bus as well too.
So it is an universal solution for a serial communication between many arduinos via serial port. Please note about possibility to connect this bus to RPi directly. ICSC lib include the library for RPi too.
Also, it's better to disable DEBUG option in mysensors config file to avoid additional traffic on the serial bus.

[shabba]

@LeoDesigner Sorry for not being clear. I was looking to connect my Arduino Mega (has about a dozen sensors and relays connected to it) to my existing RPi2 sensors serial gateway (using a UNO). I was hoping I could use a second USB/Serial port on the RPi2 to receive messages from the Mega.

[LeoDesigner]

@shabba Take a look to https://github.com/MajenkoLibraries/ICSC/tree/master/debian
It may be a starting point for you. You can adopt this part of the ICSC library to your RPi2 setup.

[LeoDesigner]

Finally I am received my RS485 modules.
Here is the working example of gateway with two nodes:

https://youtu.be/4Ls95PKLwng

[hek]

@LeoDesigner

To test this I ordered a few of these..
http://www.ebay.com/itm/381374599127?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Hope they are the correct model.

[LeoDesigner]

@hek
My modules are from http://www.aliexpress.com/item/FREE-SHIPPING-5PCS-LOT-MAX485-module-RS485-module-TTL-turn-RS-485-module-MCU-development-accessories/1718665649.html
They are the same as yours - based on MAX485.
However, it is possible to run a simple TTL signal level bus on a short distances.
(https://github.com/leodesigner/mysensors-serial-transport/blob/master/sch.png)

[hek]

@LeoDesigner

I've incorporated a slimmed down of the RS485 transport layer in this branch (soon to be merged into development):

https://github.com/mysensors/Arduino/tree/serial-transport/libraries/MySensors

But I've still haven't received my RS485 modules... Do you have time to run a small test?

Gateway:
https://github.com/mysensors/Arduino/tree/serial-transport/libraries/MySensors/examples/GatewaySerialRS485

And a test-motion sensor sketch:
https://github.com/mysensors/Arduino/tree/serial-transport/libraries/MySensors/examples/MotionSensorRS485

But you could use any example just replacing #define MY_RADIO_RF24 with #define MY_RS485

I've used the AltSerial library for RS485 communication so we can cope with dual serial ports on the serial gateway. This library requires using pins documented in sketch.

[LeoDesigner]

@hek
My example boxes are installed right now on the site and doing a daily job :)
It will take time to build a new one. I may try a breadboard, but I am still busy to finish additional improvements to mysensors.org project. (I will share them later - it's will be interesting too - I hope :) )

Actually, it's easy to test RS485 transport without a RS485 converters - just use a simple schematics I have been talking before.
Also, you may want to look to this: https://github.com/MajenkoLibraries/ICSC/pulls
It's untested support for SoftwareSerial option for library.
With AltSerial we will be forced to use only a documented pins.

Anyway - I am glad to contribute a bit to great mysensors community.

[hek]

Thanks,

@LeoDesigner said:

With AltSerial we will be forced to use only a documented pins.

Yes, I know. But AltSerial can handle higher speeds. I preferred that over the SoftwareSerial flexibility regarding pin selection. Hope I did the right choice ;)

[LeoDesigner]

@hek
Speed is one of the reasons why I have decided to use hardware serial. :)
But we should be flexible and universal as much as we can. I had been thinking also to add support for over the wire firmware update. As you have done with wireless.

[hek]

With a new bootloader? Using external flash+DualOptiBoot it should work already.

[LeoDesigner]

@hek
Sure - but it can be possible done with standard bootloader - we just have to emulate standard Arduino sketch upload process on the gateway side. But I am not sure if it's possible to do with half duplex protocol. Just an idea.

[hek]

Interesting idea. Looking forward hearing about your results.

[tbowmo]

@LeoDesigner

If using the standard bootloader, wouldn't it break the FW update if one of the other nodes on the bus starts to transmit?

[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?