DV hotspots – ZUMspot
By Toshen, KEØFHS – last updated Jan 2018
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- Introduction to hotspots
- Playing with Pi-Star
- Pi-Star notes
- Zooming around with the ZUMspot
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Zooming around with the ZUMspot
Updated for firmware v1.1.0
The ZUMspot RPi UHF Hotspot Board is a multimode digital voice modem created by the MMDVM team.
After 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!
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.
As 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:
- ZUMspot RPi UHF Hotspot Board announcement, 2017
- ZUMspot Review, 2017, by Craig, W1MSG (video)
- ZUMspot & MMDVM Demo page, 2017, by Ron, VE1AIC (blog)
- ZUMspot with Pi-Star, 2017, David Cappello, KG5EIU (Presentation)
2) ZUMspot – Summary thoughts
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!
 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!
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:
- Better battery life – The Alchemy Power Pi-Zero-UpTime takes a single type 14500 3.7V battery. The one I found has a capacity of 1200 mAh. That gives me about an hour of uninterrupted time until I need to plug in again. That means I need an external battery pack for any significant time away from an outlet. What's the point? Alchemy Power makes a UPS for the RPi 3, the Pi-UpTimeUPS, which takes two type 18650 3.7V batteries. EBL makes a type 18650 battery with a 3000 mAh capacity. 6000 mAh should provide significantly more time away from an outlet.
- Integrated on/off switches – I don't keep my hotspot on all the time, and the UPS feeds continuous power to the RPi unless you unplug the micro-USB cable between the UPS and RPi or the battery drains. I want to be able to turn off the power between the UPS and the RPi as well as the external power to the UPS, and I don't want to have to unplug cables each time I want to do that.
- No external cables (other than an optional recharging cable) – What's the point of making a super small hotspot case if it needs a bunch of cables dangling outside of the case? It's a funny thing, but with the advent of these small computers, the RPi 3, and even more so, the RPi Zero W, the cables are some of the biggest components!
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:
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.
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.
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.
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 cables and switches determined the depth of the box. Here you can see them crammed into the remaining space.
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.
(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:
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:
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
In 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.
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″
 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%.
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:
⇄ Give me a holler!
ke0fhs at toshen.com