John's Musings

Yeah, Me Neither

DVMega Hotspot OLED Wiring.....And easy firmware update

The DVMega is one popular Digital Mobile Radio (DMR) Hotspot for connecting to UHF (or VHF if so configured) networks. In the event there is no physical repeater nearby you can access the Ham Radio DMR networks via the internet. It opens Ham Radio up from the handful of old guys in your coverage area to techies worldwide. As I heard one old Ham comment "This is too easy" reminiscent of the days where you spent big bucks and mounted gigantic antennas outside of the house. Then you tuned and aimed said antenna, etc. etc. etc.

Now you can plug a hotspot in and buy a cheap DMR radio and talk to the whole wide world. There are plug and play solutions such as SharkRF OpenSpot but for a guy like me building the hotspot is part of the fun. And it is just a hair cheaper.

So anyone can buy a DVMega for a Raspberry Pi and plug it in and it works but the DVMega has one cool trick up its sleeve. You can add a monitor of some sort to display the call signs and network status. Soon as I found out you could do it I was hooked as I have several cheap OLED SSD1306 modules laying around here. Then came the realization that nowhere is the procedure documented. Oh, you'll find a wiring diagram here and there but simple, Barney style instructions are just not out there. And that's what I always strive to do.

Assumption time. I am under the assumption that you have a working DVMega hotspot on a Raspberry Pi 3 using Pi-Star OS. First of all get you an SSD1306 OLED I just linked this one for ease but I bet you can find much cheaper ones out there especially on eBay. Shouldn't spend more than a few bucks for one.

The wiring is very simple. It is only 4 wires, however a little soldering is required. The soldering will be done on top of the DVMega board however there is no fritzing part for DVMega so I drew it with the raspberry pi 3. We'll be able to figure it out!

There are 4 connections:

VCC goes to Pin 1 on Raspberry Pi

SDA goes to Pin 3 on Raspberry Pi

SCL goes to Pin 5 on Raspberry Pi

GND goes to Pin 9 on Raspberry Pi

Now as I said we have to do the soldering on top of the DVMega. Here's how those points transfer on top of the DVMega:

And here's what it looks like soldered.

Now lets configure it in Pi-Star. This is the part I could never find on the internet. Just go to your Configuration Page and Select OLED, then reboot. That's pretty much it.

Should look about like this once you've rebooted.

Now lets upgrade the firmware. There are a couple easy ways to do this but by far the easiest is to remove the Integrated Circuit chip from the DVMega and flash it on an Arduino R3 Uno. HOWEVER, bend one leg on the chip and break it and it's over. You are done. So here's what I recommend. Buy some additional chips. They are just a few dollars each. What you need is an Atmega328-PU Chip aka Arduino Bootloader Chip.

Don't touch the DVMega yet. First let's take one of these new chips and install it in the Arduino R3. Make sure the little tiny half circle notch is on the end of the board.

Now go to the DVMega Download page and download the X-Loader and the latest version of the firmware for the DVMega platform you have. (Mine is Raspberry Pi and the shipped mega I got had version 3.18 and a version 3.19 is now available).

Once downloaded hook your Arduino up to your computer, run the X-Loader program and select your board (Uno) and the proper firmware file and then hit the "Upload" button. That's it. Only takes a few seconds.

Now VERY VERY VERY carefully remove the chip from the DVMega. Gently pry up from both ends or use a proper chip pulling tool. If you don't have one just lift a tiny bit on one end, go to the other end and lift a tiny bit. Rinse, lather, repeat. Do it slowly. The pins will bend Oh So Easily. Likewise, remove the chip from the Arduino also making sure the notched end is near the end of the board. (Refer to my pic above with the soldered OLED on it. The notch is right on the board edge. Don't put it in backwards.

Now boot Pi-Star and Voila'

DVMega HR3.19

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