Hello!

Can someobe please answer, if I can do all my wishes with Carambola 2?:

a) Linuxbased and can run my own Java/C++ application?
b) I can disable openWRT? I need no Webserver or other Routing features!
c) IPv6 is possible?
d) The 2 Ethernet ports can I set as 2-Port switch?
e) I can use 12 outputs and 8 inputs?
f) How long does it take until Linux is complete booted?

Thanks!!

hanhoe

Hi hanhoe,

I'll get straight to the point:

a) Yes, although Java is not recommended, but if you build/install JVM it works.
b) OpenWRT is a linux distribution name, so you can't disable it as per say. You can however disable the services and set it up in a way that you like.
b (routing), c, d) Yes, but you should be familiar with linux network configuration.
e) Do you mean GPIO? Carambola2 has 23 GPIOs, but on the development board only about 12 of them are usable. However you can use GPIO extender chip.
f) About 30 seconds to serial console.

Hi Giedrius!

Many thanks for your answer!
a) Ok, maybe I wrote a C++ application or maybe also Pyton
b) Ah, ok ... well, then I just have to disable Webserver and other function. I already read about image generation
c) + d) I hope I found this in other forums. Configure a Linux should be possible by me (and internet)
e) Yes, i see. So I try to use I2C communication. Then I can expand the Inputs and Outputs
f) hmmm ... thats long ... this mean my application is in around 40sec ready? Does it helps to disable functions that I don´t need?

Wish you a good start in the week!

Hi Giedrius!

There is one more question!

I guess when I set the 2 ethernet Ports in Linux as switch, the latency is much higher as a "real" switch, right?

I would connect 30 Carambola 2 as Daisy Chain ... so I think now, the last module has a high latency.
But maybe you can tell me how much it is?

Thank you!

I have no experience with such exotic setup, so can't give any real numbers. However, theoretically the packet roundtrip in linux kernel + drivers is around 1-2ms (assuming no heavy traffic), which gives 30-60ms for the end node. If you want less and are brave enough, you can dive into linux driver waters and configure the hardware switch in a way that you want - this should give you less than a millisecond roundtrip per node, so less than 30ms end node delay (once again at no heavy traffic).

Hello Giedrius!

Thank you!
I will search in den Internet for such information and try to build a absolute minimum Image of openWRT.

Maybe you know which module in the image pack I doesn´t should delete? I doesn´t want to "kill" the bootloader and then I can´t flash again.

Thanks!

sysupgrade command does not alter bootloader, so as long as you use it to upgrade firmware, everything should be fine.

Oh, perfect.

Just to be sure: i use this methode to build image:
http://www.8devices.com/wiki/carambola:2:gettingstarted

So it is not dangerous?

hanhoe

Everything on that page is safe and by that I mean "device can be recovered by software". Even if you install a corrupt linux image, you can still recover it from a bootloader.