MobiFlight Community Support

Hi there,

I'm (still) building my kinda Homecockpit, but not a huge block filling a room, but more a mobile one consisting of several boxes each in the size of a normal briefcase.

One of these boxes is my "Base Box", where amongst others the central external 5V power supply will be placed and from here should be the only connection the PC

Now i have the challenge that i have to inter-connect the boxes and this should look "nice" as well.
In some cases will be Megas as well, and there could be two boxes sharing one Mega, not to waste many unused pins.

As far as i know, when connecting several Megas over an active USB-Hub to the PC, the cables between Mega und Hub should be quite short.
But what about the cables from the Mega to the controls like switches, Maxes, ....? Are there any known limitations regarding the length?

So my idea is: placing all (!) Megas in one extra case and from here connecting all the other boxes with the controls with flat cables.
Good idea? Bad idea?

Thanks so far

Kai

Hi

Basically as you aleady expect.... Myself and all people i met have the same basic rule.... "As short as posible !"

But for sure there are a lot of exceptions.

The most critical part i know is the Max7219 ..... Here i will say we need to work as short as it get.
I not know what part is more sensible .... the line from Max to Display or the line from Arduino to Max ( or from max to max in a chain)
Here i simply limited myself and say never more then 30cm. If possible then directly nearby with a fixed connection or PCB and fully without wires.

I think also all other Elements with a high rate of data .... E.g. a LCD or a Stepper can be problematic with long wires.

On the other side... A simple On/OFF LED (not sure if PWM is a factor) or a ordinary Switch have no problem with a length of 50cm or 100cm.
Pretty sure the qualitiy and material of the wire is a important factor. 5 volts 20mA The "self resistance" of the Device and the wire is the point.

********
Same logic also for the USB. I think high qualitiy expensive USB Cables pretty sure also work in a greater length. Bad covered cables may get in trouble already after 30cm or more.
Maybe its fully nonsense.... But i would say the length of the Cables from your single boxes to the "Masterbox" can be a little longer pretty sure.
The Line from Master (Hub) to Computer i would make shorter.
Cause on the "Inbound" Lines there is only comunication from 1-2 Arduinos.
On the Master Line there is comunication from all Megas together.
I expect this is no factor official. Its just a logical result of my thoughts !


*********
About your planings.
Here you can do what you like pretty sure.
I just can repeat my main statement.... NOT Care about the number of Megas.
You Build e.g. 10 Boxes.... So use 10 Megas ( or maybe more if one box need more then 68 Pins)
Its no mater that 4 Boxex e.g. use only 15 Pins each, so you could technical wire all 4 to one single Mega.
The main idea from your Box System is to have only one single cable out of each box. ( Or a second 2 line Cable if you need ext.Power)
Why kill this logic by using Flat wires. Why get into a risk of loosing data with that idea? Just to save Megas ?
Also a round small Black USB Cable looks better as flat wires from Box to Box ! And you not need to buy and build the Flat Connectors IDC.

I know my philosophy is extremly here. But if i would need 1 single switch external of my planings..... I would use for that switch a own Mega, let 67 Pins empty and all is fine for me.
I would also never use Micro, Uno or so. Whatever i would only need 5 Pins on it.
Its a factor that Mega runs well all the time . Micro runs now after a lot people improve the Firmware BUT its an the upper end of recources.
My mega will work also with Mobiflight 10.x 11.x and 12.x garantee But I not know if a Micro will also do if we get new features and the micro run out of Mem again!

*****

Summary:
For ME ( i not talk for all users and not for the MF official policy)
I would use Megas Only in the Boxes and i would use a USB Wire ( And a Power wire if needed) from all Boxes to your Master.
From the Master there is then just one USB Cable to Computer and a Power Cable to a 230v Socket
No Flat wires, no risks, celan and easy to connect. But yes. Some Megas more, a greater Hub maybe.
Costs: Nearly the same. Cause IDC Connectors for Flat Wires are not so cheap as you expect !

Sounds reasonable, especially the cost factor.

You're right, some IDC connectors with the cables etc. could cost the same (if not even more) than one Mega.
Well, then lets be wasteful with the pins.....

I will connect the "external" boxes with one USB-cable each with the Hub mounted on the Base-Box and from there to the PC.

Thanks for your thoughts, pizman.