DV hotspots – ZUMspot

By Toshen, KEØFHS – last updated Jan 2018
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Zooming around with the ZUMspot

ZUMspot logo   

Updated for firmware v1.1.0

The ZUMspot RPi UHF Hotspot Board is a multimode digital voice modem created by the MMDVM team.

MMDVM boardAfter watching ZUMspot Review, a video by Craig, W1MSG, about using the ZUMspot with Pi-Star, I was convinced to give it a try. I'm really glad I did; it's a brilliant little board!

I decided to pair it with a Raspberry Pi Zero W, which I prepped by installing the Pi-Star image and then setting up wireless connectivity.

Because I had that much done and already was familiar with Pi-Star, when the ZUMspot arrived it took almost as long to get the bubble wrap packing material off as it did to get it set up via Pi-Star and linked to a D-STAR reflector, and then a DMR talkgroup as well.

MMDVM boardAs an aside, the RPi Zero W is such a cool little board! It wasn't that long ago that I was blown away by how small and capable the RPi 3 is, and here's the Zero W, so much smaller while still quite capable. And only $10!

Here's the ZUMspot + RPi Zero W sitting on top of my DVMEGA + RPi 3 in its Flirc case. Hats off (on?) to the Raspberry Pi Foundation folks; they are doing really nice work!

1) Learning about the ZUMspot

I began getting ready for the ZUMspot's arrival by reading and watching everything I could find related to it. Some good finds include:

2) ZUMspot – Summary thoughts

Thumbs up! Thumbs up!

In my opinion, the ZUMspot is definitely the digital voice hotspot to get right now. It's multimode-capable (D-STAR, DMR, Yaesu System Fusion, and P25²), is perfectly complemented by Pi-Star, costs less than $100, and works nicely paired with a $10 RPi Zero W.

Thanks for creating a really nice hotspot solution, MMDVM team!

[2] As of late Dec 2017, I read in the Pi-Star Users Support Group that Jonathan Naylor is working on adding MMDVM support for NXDN, a digital voice standard jointly developed by Icom and Kenwood.

3) ZUMspot + Pi-Star – An invitation to play more

For fun, I decided to make my own case for the ZUMspot hotspot out of some mahogany thinwood I had.

3a) Zumspot + Pi-Star hotspot – v1

I mounted the ZUMspot + RPi Zero W on a similarly small board with a rechargeable battery, the Alchemy Power Pi-Zero-UpTime, which functions as an Uninterrupted Power Supply (UPS) and portable battery pack. I also added a 3.2″ Nextion display for fun. Then I made a custom mahogany case for the whole thing.

I can sit this unit on top of my radio shelf plugged into a normal AC power supply adapter and connected to my home WiFi network to function as a digital voice base station, or I can unplug it—with no interruption to what's going on—to run off the battery, and then put it in my car connected to my phone's hotspot for a mobile solution. Versatile!

ZUMspot + RPi Zero W + Alchemy Power Pi-Zero-UpTime
ZUMspot connected to Nextion display
ZUMspot, Pi-Star, DMR, in mobile mode

For more info, see Connecting Pi-Star via cell phone

3b) ZUMspot + Pi-Star hotspot – v2

After playing around with my v1 hotspot, I decided to make some changes:

So I decided to build a v2. Since Pi-Star can run headless, as long as on/off switches are incorporated, the hotspot really doesn't need any ports except for power in for recharging. It basically can be a black box (or a mahogany box) with an antenna, on/off switches, and, optionally, a display screen.

Here's the basic setup I ended up with, ZUMspot + RPi 3 + Pi-UpTimeUPS:

ZUMspot connected to RPi3 and Pi-UpTimeUPS

Next I needed to incorporate the on/off switches and display. There aren't a lot of choices for micro-USB on/off switches. The best option I could find is the LoveRPi Power Switch, which includes a green status LED showing when it's on (important in a black box scenario). It includes three rubber covers for the switch itself: green, red, and black. Though it strikes me as a bit big, it's the smallest I could find available.

LoveRPi Power Switch

The good news is that I can reduce the footprint of the display by soldering wires directly to its back rather than using the connector that plugs into the side. Also, since I'm using those same soldered wires to connect the display directly to my PC for programming via a USB to TTL UART CH340 Serial Converter, I don't need to leave space (or cut a slot) for inserting a microSD card into the display. That means I can incorporate a 3.5″ display in the same space needed for the 3.2″ display in the v1 hotspot, which used the plug connector and had space for the microSD card.

Back of Nextion display showing wiring

Then I made another custom mahogany case, but this time using a simple rectangular box shape: 4.5″ wide × 4.7″ deep × 3.5″ high. The space needed for the 3.5″ Nextion display determined the width required, but the boards themselves are only slightly less wide.

ZUMspot hotspot v2

I added a plexiglass base to the stack of boards, and the resulting stack determined the height of the box. The boards slide into the box and are held in place by a rectangle of wood that anchors the plexiglass base.

The stack of boards anchored inside the box

The cables and switches determined the depth of the box. Here you can see them crammed into the remaining space.

The stack of boards anchored inside the box

The power switches and the single port, the micro-USB power input, are located on the back of the box. The cable with the green switch controls power between the UPS and RPi. The cable with the black switch controls power between the input port it provides and the UPS.

The back of the box with the power switches

(If I were to do this again, I'd use a short micro-USB male-to-female extension cable to provide the input port instead of the cable with the black switch.)

Here's a comparison between my ZUMspot hotspots v2 and v1:

Side-by-side comparison of the v2 and v1 hotspots

Considering that v2 is self contained with 5× the battery capacity (adequate for a few hours of use), built-in power switches, and no external cabling except when it's recharging, I'm pretty happy with how compact it turned out.

3c) ZUMspot + Pi-Star hotspot – v3

After playing around with the v2 hotspot, I realized that as much fun as the display is, it's not really necessary, especially on the road, and eliminating the display would increase the battery life. So I decided to make another version, a hybrid of v1 and v2. The v3 hotspot has no display, contains all the cables within, and uses the RPi Zero W and the Pi-Zero-UpTime. It runs about 90 minutes before needing to be plugged in.

Here's a comparison between my ZUMspot hotspots v2 and v3:

Side-by-side comparison of the v2 and v3 hotspots

V3 has a single power switch that controls power between the UPS and RPi. I found a right-angled female-to-male micro-USB adapter (Ksmile) that provides the power input port.

Because there's no display, I drilled a few holes in order to be able to see the most important LEDs, the charge in progress/complete LEDs on the Pi-Zero-UpTime, and the power LED on the ZUMspot.

At 3.2″ × 3.2″ × 2.7″, this makes a better size for use in the car.

3d) ZUMspot + Pi-Star hotspot – v4

RAVPower 10050 mAh portable chargerIn the end, the Pi-Zero-UpTime's 1200 mAh battery just doesn't have enough running time for what I want. So I decided to go for a minimalist mobile hotspot design, with a box for just the ZUMspot and RPi Zero W, powered by an external ruggedized RAVPower 10050 mAh portable charger, which has a similar footprint.

I added a right-angled micro-USB adapter to make plugging in easier (it aligns better with the port on the charger), as well as to reduce wear and tear on the RPi's micro-USB port.

ZUMspot hotspot v4 sittinng on battery

The small mahogany case fits nicely on top of the charger, which should give me a full day's capacity¹. For comparison:
                 Width  Depth  Height
Hotspot case v4:  3.2″ × 2.5″ × 1.1″
External battery: 4.6″ × 2.8″ × 0.9″
Hotspot case v3:  3.2″ × 3.2″ × 2.7″
Hotspot case v2:  4.5″ × 4.7″ × 3.5″
Deck of cards:    3.6″ × 2.6″ × 0.7″

[1] I ran this hotspot for 20 hours straight off a RAVPower Ace Series 32000 mAh portable charger while monitoring both a busy D-STAR reflector and a busy DMR reflector. Afterwards, the charger still had 4 LEDs showing, so the remaining charge was somewhere above 76%.

ZUMspot hotspot v4 in action with D-STAR and DMR

I think I'm finally satisfied with my ZUMspot hotspot setup, with the winners being v2 for my base station and v4 for mobile. Here's a comparison between the two:

Comparison of the v2 and v4 hotspots

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