Chuwi Larkbox Pro Off Grid Power

Hello Operators.

Recently the Larkbox Pro from Chuwi was introduced on the channel, as an effective low power yet capable mini PC for ham radio field communications. It was introduced to fill in where the raspberry pi couldn’t fulfill all of our communications requirements. You can watch that video here. Skip to 09:30 to go right to the relevant place on the timeline.

The LarkBox Pro was interesting because of reasonably powerful CPU, low power draw, and small size. Another interesting feature was what we thought at the time, was power over USB-C PD, which turned out to be fake (underutilized :)). This is why my Anker USB-C PD adapter didn’t know what was going on with the LarkBox Pro. Neither did my USB-C PD Powerbanks.

The Power Supply supplied with the LarkBox Pro has a USB-C connector, but that is as close as it comes to being USB-C compliant. In reality, it is just a 12 volt 2 amp power supply, delivering its power to a USB-C connector. It seems the pins are wired correctly in the connector, but there is no data or logic along with it. I would recommend NOT using this supply to charge your flagship smartphone, tablet or Macbook Pro. How our Chinese friends love their engineering shortcuts. 😃 In this case the shortcut is good for off grid use or battery power, since the LarkBox Pro simply requires a stable 12 volt source. A source like the PowerFilm Lightsaver Max.

Well after some quality time with the fluke, the great mysteries of the universe have been revealed. The power supply puts out 12.1 volts, and a maximum of 2 amps. Fair enough! What we don’t know is how tolerant the LarkBox Pro is to minor voltage variations. This is also OK if using the PowerFilm Lightsaver Max, since it’s output is well within the +/-5% voltage variation I’m willing to risk.

After jerry rigging up the wiring between the Lightsaver Max, inline multimeter, and the LarkBox Pro, I tested with Winlink Express, the Xeigu x5105 with the DigiMode-4 interface. The Lightsaver Max was powering everything, but we were only measuring the voltage of the LarkBox Pro, and Digimode-4 interface. Here are the results.

Aftwards, I tested with JS8Call and the Icom IC-705. The Icom ic-705 had its GPS enabled, and was sending NMEA data to the LarkBox Pro, which was used by GPS2Time, to adjust the LarkBox Pro clock to within tens of milliseconds accuracy. Here is the result. This seems a little high, but with GPS NMEA being streamed from the 705 to the LarkBox Pro, it may be ok.

So the LarkBox Pro can definitely be used for off grid computing needs. We would have hoped Chuwi would have documented to freakin power port, so we would not have had to jump through hoops to figure it out. OK, it wasn’t that difficult to reverse engineer, but we should not have had to do it. What I learned was the original graphic showing the LarkBox Pro consumption was done using the AC power supply, rather than using an inline meter to measure the LarkBox Pro alone. I am not certain how much overhead the AC power supply added when being connected to mains, but these results are much better than expected. At idle, the LarkBox Pro is only slightly more hungry than a Raspberry Pi 4 B. Add GPS and USB powered Audio Interface to the Raspberry, and the LarkBox Pro comes out on top, when both are powered from a DC source.

Instructions

  • Remove the LarkBox Pro power supply from mains power.
  • Cut off the LarkBox Pro power cable as close to the power supply as you require.
  • Take the cable with the USB-C connector and trim back the outer covering to expose the red and black wires.
  • Separate the red and black wires from one another, and trim off the the insulator.
  • I choose to use Anderson Powerpoles, but a barrel coaxial connector can work as well. Fit your desired conencor type to the red abd black ends of the power wires. Red was positive, black was negative. (You can lso install a fuse inline at this point if you like).
  • Do the same for the power supply pigtails left over after removig the cables. This allows you to continue using the power supply, but now the cable is modular.
  • If your DC source is more than 5% +/- of 12 volts, I would suggest adding a buck convertor between your DC source, and USB-C connector which goes to the LarkBox Pro. Adjust it for 12.1 volts, and place it inline between your DC source and USB-C connector on the cable you just made. My setup looks like this (for testing). I’ll clean it all up later.

So you see, it really was a simple matter to get an off grid capable LarkBox Pro up and running, despite poor documentation from the manufacturer. So far my LarkBox Pro has been running well. I have no regrets about it, but time will tell if it is a solid counterpart to the Raspberry Pi.

My use case for the LarkBox Pro is as a communications computer running within my basecamp or field station. The LarkBox Pro is connected to my radio equipment, running Winlink email and/or JS8Call with one or two radios. The LarkBox Pro provides a VNC connection to its desktop, allowing multiple radio operators to utilize the applications running on the LarkBox Pro, wirelessly from their own devices. The device could be a laptop, tablet, smartphone, … The main point here is communications are running via the LarkBox Pro, despite there not being a radio operator sitting tirelessly in front of the radio. There are always other tasks to do in a basecamp or field station. Chopping wood, making food, sleeping, … The LarkBox Pro, Raspberry Pi or whatever Mini PC you might be deployed, runs our asynchronous communications while we are managing the rest of the camp or station.

If you’re interested in purchasing a LarkBox Pro from Chuwi, mine came from ebay: http://ebay.us/JdrsJY (I may earn some commission at no cost to you, through this link, which helps keep the channel/blog running).

73
Julian oh8stn
YouTube: http://www.youtube.com/c/oh8stn
TipJar: https://paypal.me/oh8stn/1usd (Everything helps)

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