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View Full Version : Onboard coprocessors/DHCP at events

fovea1959
20-02-2015, 16:32
We've going with a second computer on-board this year for the first time.

In years past, everything got static addresses, so our setup would have worked at home, on the field, and in the pits (where we have no DHCP).

This year, everything is using DHCP and letting mDNS sort things out (thank you, FIRST, this was a relief when switching between the robot and the school network).

but...

at the event, are we going to have to switch things back to static addresses so they work in the pits? or is there a better solution?
Joe Ross
20-02-2015, 22:19
Are you using mDNS to find the coprocessor? If so, it should continue to work as long as the coprocessor assigns a link local address when there isn't a dhcp server.
fovea1959
22-02-2015, 20:04
coprocessor is Debian-based, and we have avahi installed so we would have mDNS working, and avahi-autoipd takes care of allocating a LL address, so all is well. tested with roboRIO, coprocessor, and laptop on a hub with no DHCP in sight....

never done zeroconf before, this is pretty cool!
billbo911
22-02-2015, 20:22
Our on board coprocessor is using the static address 10.20.73.25.
Is this going to cause an issue?
Joe Ross
22-02-2015, 20:36
Our on board coprocessor is using the static address 10.20.73.25.
Is this going to cause an issue?

Based on http://forums.usfirst.org/showthread.php?24165-DHCP-on-the-field you should choose an IP address outside of 20-199 and shouldn't expect the roboRIO or Driver Station to be at a certain IP address.
billbo911
22-02-2015, 20:53
Based on http://forums.usfirst.org/showthread.php?24165-DHCP-on-the-field you should choose an IP address outside of 20-199 and shouldn't expect the roboRIO or Driver Station to be at a certain IP address.

Thanks Joe! Simple change.
fovea1959
22-02-2015, 21:44
billbo911: I suspect that when you are in the pits or on the practice field at an event with the radio in bridge mode, you won't have any DHCP server, so your laptop and roborio will come up with a 169.254.x.x link local address, your coprocessor will be 10.xx.yy.zz, and your coprocessor won't be able to communicate to the rest of your setup. That's only in the pits or on the practice field.

This was the situation I was worried about, but Joe advised to make sure that everything fell back to using a link local address, and that seems to be ok.

is your coprocessor Linux based? if so, install the avahi utilities, and they will take care mDNS and link local addressing.