Communication between 2 Bela Mini

giuliomoro

Not sure why the DHCP is not picked up on the host ... try manually setting the IP address for the new interface to 192.168.8.1 (note the .1) and then try to access the IDE ad 192.168.8.2 (note the .2) again.

On the board, ensure when you run ip a you get usb2 with IP 192.168.8.2

FelixDoyon

giuliomoro Not sure why the DHCP is not picked up on the host ... try manually setting the IP address for the new interface to 192.168.8.1 (note the .1) and then try to access the IDE ad 192.168.8.2 (note the .2) again.

How can I do this? I tried those settings but I don't think they are good

giuliomoro

FelixDoyon How can I do this? I tried those settings but I don't think they are good

That looks good , assuming it's done on the "new" interface that only shows up with the USB-A -> USB-A connection.

FelixDoyon

It doesn't seem to work. I've double check to do the settings on the good one

FelixDoyon

Never mind! It work. I just switched the address of ip address and ip gateway

FelixDoyon

So, for now, if I want to communicate between the 2 Bela, I need to

Do the same on the second one, but with different address (for USB A port and micro USB port)
Create a UDP object in script
Send UDP packet to the appropriate IP of the USB A

Is that correct?

giuliomoro

FelixDoyon Would it be better if they are both connected from the same source?

Is this what you are planning?

                  COMPUTER
192.168.6.1                     192.168.9.1
-------------------------------------------
USB A                                 USB A
|                                        |
|                                        |
USB micro                            USB micro
V                                        V
192.168.6.2                       192.168.9.2
Bela <--host USB A ---- USB A device--> Bela
Mini 192.168.8.1            192.168.8.2 Mini
 1                                       2

In this case, it may be fine without hw modifications because they are both being powered by the same 5V source, so the voltage will be the same shouldn't have any current going through.

FelixDoyon Do the same on the second one, but with different address (for USB A port and micro USB port)

You don't need to do the same on the second one: the stock one will act as the host and the modified one as the device. You do need some changes, though.

Assume BelaMini 1 is the stock one and BelaMini 2 is the modified one. Look at the diagram above: each USB cable is a network interface visible only to the two devices that are connected to it. The computer would see both devices on 192.168.6.2 and so won't be able to tell them apart. You have to modify the IP range of one of the two Belas so that it doesn't overlap. The easiest way is to further modify BelaMini 2:

in /etc/network/interfaces find the section for usb0 and change it to use the 192.168.9.x subnetwork:

auto usb0
iface usb0 inet static
    address 192.168.9.2
    netmask 255.255.255.0
    network 192.168.9.0

in /etc/dhcp/dhcpd.conf, add another entry to give out DHCP addresses on that network:

subnet 192.168.9.0 netmask 255.255.255.0 {
        range 192.168.9.1;
}

BelaMini 1 will also need to see the other board, which shows up as usb2 as 192.168.8.2, so it needs to either dhcp on that port or - if it fails - set the IP statically. The static IP is set by editing /etc/network/interfaces on BelaMini1 and adding:

auto usb2
iface usb2 inet static
    address 192.168.8.1 # note the .1
    netmask 255.255.255.0
    network 192.168.8.0

Side note: if this is your actual use case and the only reason for the USB-A <-> USB-A connection was to have both boards accessible from the host computer at once, then there would have probably been easier solutions via forwarding some ports over ssh that would have made the setup easier when plugging one Bela's USB-A into the other's USB-micro. This would have allowed to even access the IDE of both boards over a single connection to the host. Accessing the scope may have been more of a problem, though.

giuliomoro

OK. Now you could make /opt/Bela/usb1_network.sh run automatically on boot by running it as a service, following the instructions here.

Now, for connecting this to two different computers at once, one important thing is that the 5V lines from both USB ports (B-micro and A) will be shorted together on the PB and so if the voltage is even only slightly different you'll get large currents flowing through that will lead to excess power consumption and possibly damage the board. There are a number of workarounds for that:

cut one pin between BelaMini cape and PocketBeagle
instead of using the USB-A cable, slice open a USB cable and wire it manually to the pins on the header, without connecting 5V
use a breakout board like this one and do not connect 5V

Additionally, if you need the board to be powered when connected to either source, then the 5V line from this extra USB should be wired to P1.01.

FelixDoyon

Would it be better if they are both connected from the same source? If there is no better option, I will order a Usb A breakout

FelixDoyon

giuliomoro

giuliomoro Side note: if this is your actual use case and the only reason for the USB-A <-> USB-A connection was to have both boards accessible from the host computer at once, then there would have probably been easier solutions via forwarding some ports over ssh that would have made the setup easier when plugging one Bela's USB-A into the other's USB-micro.

The final goal to this is to have a digital wired communication between 2 micro controler from 2 diffrent computer in 2 distinct room, to cast live audio from both room in the other one with the smallest latency and by digital. Unfortunatly, I've done some test with UART and I had to much transmission error to have a good sound quality, and that's why I wanted to use the USB A port (also for the ease of use)

giuliomoro You don't need to do the same on the second one: the stock one will act as the host and the modified one as the device. You do need some changes, though.

So, if I understand well, I don't need to make any chance to the second Bela Mini? It will already work with UDP via USB A port if the first Bela mini is acting as host, even if they are connected to 2 diffrent computer?

Thank you so much for your time!

giuliomoro

FelixDoyon So, if I understand well, I don't need to make any chance to the second Bela Mini? It will already work with UDP via USB A port if the first Bela mini is acting as host, even if they are connected to 2 diffrent computer?

If by "second" you mean BelaMini 1 in my diagram above, see here:

giuliomoro BelaMini 1 will also need to see the other board, which shows up as usb2 as 192.168.8.2, so it needs to either dhcp on that port or - if it fails - set the IP statically. The static IP is set by editing /etc/network/interfaces on BelaMini1 and adding:

auto usb2
iface usb2 inet static
address 192.168.8.1 # note the .1
netmask 255.255.255.0
network 192.168.8.0

FelixDoyon The final goal to this is to have a digital wired communication between 2 micro controler from 2 diffrent computer in 2 distinct room, to cast live audio from both room in the other one with the smallest latency and by digital.

Can't say any of these is the best approach for the job: latency will be larger via USB and you'll need buffering on both sides, not to mention clocks drifting between the two units over time which means latency will slowly change over time. But good that you are giving it a try.

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