Architecture advice

I'm think of using the IOT2020 (or 2040, or 2000) for a project I have coming up.  I want to outline the high-level requirements and solicit advice on the best way to approach the problem.

50 IOT units, each talking to 10 i2c devices on a custom PCB.  The IP addresses will identify which device is plugged in where (cisco option 81 (82?) should dole out ip based on port location).  Central control will be accomplished with MQTT where configuration variables are published to the IOT units and readings read from MQTT variables on the IOT units.  Data rate ~5 readings at 1Hz.

I'm trying to figure out which way to jump, whether to go Arduino or straight C++ for execution.  The application itself should be relatively straightforward (psuedocode, fill in the blanks on function calls):

while(1){

readMQTT_Settings(&settings);

if (settings != oldSettings) {updateI2cChipSettings(); updateGPIO();}

readI2CA2Ds(&readings);

publishMQTT_readings(readings);

sleep(500);

}

 A couple of things are hanging me up though.  The Arduino MQTT library looks like you need to hardcode in the MAC address.  I'm going to have 50 of these, so this needs to be dyamically populated.  I want to just be able to say something like MQTT_Setup(127.0.0.1,'user','password').  Is that more doable with a standard C++ program than an Arduino sketch?

At the end of the day, I'd really like to be able to roll up the final package into an image to write out to the other 49 boxes with as little post-setup modification as possible once deployed.

Any advice would be appreciated,

Mike

Dear mwebster,

not really a nice solution, but the following should work

* ping and read the reply back into application, try  to connect to existing IP on silly tcp port and extract Mac from answer (connection refused) (this should work at least in C / C++)

* result writing into a txt file

* parse the txt file from arduino sketch

Bye

Volker

this command returns the MAC address of the ethernet port:

Hi,

the /sys filesystem is your friend. I don't have an IoT here at the moment, but on my debian linux desktop machine I just can read /sys/class/net/eth0/address which contains the MAC address.

  Michael

I've just checked on image 2.1.3 and that works!

mwebster 

I'm trying to figure out which way to jump, whether to go Arduino or straight C++ for execution.

I'm not sure if it is possible to debug the Arduino sketches on the IoT2000, but even if there is a way, it may be clumpsy.

The Arduino libraries are written in a minimalistic design, that means for a cpu which has 1-2 kB RAM. Especially for network code this means they may be very low level and specialized for the network hardware they were written for.

These are the reasons why I would prefer the Eclipse approach.

 Thanks for the advice, I'm going the Eclipse/C route for now.  I knew there were ways to get the MAC address in Linux, but then I have the issue of accessing the file system from Arduino-land which doesn't seem straightforward. 

I do have some issues getting debugging working in Eclipse, but I think that has to do with the TCF configuration and I'm going to ask about that in another post.  If worse comes to worse, I'm starting to learn how to use gdb through the shell...

 Hi,

mwebster

The Arduino MQTT library looks like you need to hardcode in the MAC address. 

 

Today I was trying the Adafruit MQTT library. I had to modify the library , because it didn't compile for the Galileo but then it worked.

You don't need the local IP-address or MAC-address in the sketch, actually the whole "Ethernet" class is not needed for the IOT2000/Galileo because the interface it is already configured by the linux OS. Just use the EthernetClient class (and the "EthernetClient.h" header).

See also the example I uploaded in another posting (just TCP, no MQTT).

mwebster

I want to just be able to say something like MQTT_Setup(127.0.0.1,'user','password').

That's exactly how it works.

/update: in the attachment you will find a MQTT example including the Adafruit MQTT library adapted to the IOT2000/Galileo.

  Michael

mwebster

 Thanks for the advice, I'm going the Eclipse/C route for now.  I knew there were ways to get the MAC address in Linux, but then I have the issue of accessing the file system from Arduino-land which doesn't seem straightforward. 

I do have some issues getting debugging working in Eclipse, but I think that has to do with the TCF configuration and I'm going to ask about that in another post.  If worse comes to worse, I'm starting to learn how to use gdb through the shell...

 I have the debugger working with Eclipse NEON. 
Instructions: https://www.rs-online.com/designspark/debug-iot2000-c-program-with-eclimse-neon-and-windows10-64-bit