Multitech woes

A project log for Basic Farm Robot 2021

Minimal 'no frills' development platform for farm robots

capt-flatus-oflahertyCapt. Flatus O'Flaherty ☠ 08/31/2021 at 17:520 Comments

Wifi Network woes.

Our first task was to get a stable wifi connection to the robot. The only thing we has available that was IP68 rated for out door used was a multitech MTCDTIP-LEU1 wifi/lorawan/4g combined access point/gateway. It was quite flexible as it had power over Ethernet, so we could mount anywhere we could run a Ethernet cable.


This seemed like a good choice , as we could mount it in the central field where the robot would be tested, making our wifi transmission distance optimal. We made a make shift 'mast' and mounted the multitech to it.

Our initial tests were good, we go good 2.4ghz wifi connectivity to the raspberry pi's on the robot platform, even *without* external antennas on the robot. We were also using the multi tech to provide us with 4g internet access. Things were looking good!

As we started to run higher data rates, especially real time video , although the wifi chip could sustain those rates with ease, the CPU was being pegged at 100%, causing increased latency, data flow drop outs and constant wifi re-transmits and disconnections...all in all not good for robot communuications.

It's poor ARM9 processor at 400 Mhz could not keep up with the data we were shunting through it, this was made worse as we were routing on main internet 4g wan through it too. Apparently new multitechs use much beefier cpu's! :-) .

We decided to ditch the old tech in favour of  RUX industrial router boards and relegated the multitech the storage shelf once again :-(. 

We didn't go with upgraded mulitechs because they use a yocto based linux distribution and although you had ssh access to the device for configuration/ diagnostics, there was a distinct lack of packages and configuration options. We needed to do some special ethernet/wifi bridging, multicast proxy and dns configurations. The  RUX are thankfully openwrt based, so we knew we could have the flexibility of openwrt itself, great extention packages and great business quality support on top. 

The motto of this log is, even though something looks cool and may have the features you need, it may not be cut out for robotic communication, which needs low latency, high data rates and bullet proof reliability that are essential for remote robot control and telemetry tasks.