John's Musings

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Nextion Screen on KB5RAB MMDVM DRM Operating System

I've been dabbling with DMR Radio Hotspots and trying hard to build the perfect rig. Right now I am running KB5RAB MMDVM image with great success.

I'd say that it is a bit geekier to use than an image like Pi-Star You'll note that I didn't hotlink KB5RAB and there's a good reason for that. There isn't a link!

You have to join the Brandmeister TalkGroup 3148 on Facebook and once approved go to the Files section and get the latest link to the KB5RAB image. It comes with a pretty excellent set of directions as well.

I'm using a Raspberry Pi 3 and DVMega UHF board and finally added the Nextion 2.4" UART HMI Screen also to get this screen to work you will need a USB to TTL converter.

The screen is interactive and changes values which is really cool. Here's what it looks like in action. Not the greatest video but you'll get the idea.

So it's not that complicated. So basically you download the KB5RAB image and write it to an SD card. They recommend logging in via a VNC connection. If you want to use ssh right out of the chute after you write the card add a file called "ssh" to /boot. On a mac I pass

cd /Volumes

cd boot

touch ssh

Ok, done deal you should be booted into the image and now you need to configure it. But first lets go back to the Nextion screen and configure it. First you need to download the Nextion Screen Editor and then you need a file to upload to the screen. I got my Nextion screen HMI file from an excellent resource and I won't hotlink his file for a couple of reasons. One, it isn't mine and I don't want to give the appearance it is. 2nd the link is only accessible if you are a member of anyway. So you would have to make an account there. Then do a global search for 2E0XVX. Scroll way down his page and he has a link to the Nextion HMI file.

It's super easy to configure. Install Nextion Screen Editor and open 2E0XVX's file. You MIGHT have to set the device ID. I didn't. Also note that near the upper left is a box I have tagged with the frequency in it. If your simplex channel is different than his you need to change this. Note that on the right the MMDVM line is highlighted blue. and the t22 box is selected. Scroll down on the lower right pane and find the frequency and change it. You have to do it one more time for the transmit frequency. (2nd photo).

Change the transmit frequency as well, then click Upload. You may have to set your serial port slow. I did for some reason. Note that this time I have the DMR field highlighted on the upper right hand pane and I have also changed the frequency in the lower left hand pane. Now simply hit upload.

Once it completes........that's it. Unplug the screen and go back to your KB5RAB image and log in over VNC. (I actually used ssh). Open a terminal and type

sudo raspi-config

Do the following (I'm not screenshoting everything here. If you can't figure out how to change your password by looking at the pic below you're in the wrong place anyway):

- Change User Password.

- Change Host Name (optional. I have a million Raspberry Pi's. I need very unique names so I know which is which)

- Localization Options. Change your Timezone.

- Interfacing Options. (See 2nd pic)

-Interfacing Options (con't.) Select "Serial"

Login shell = no

Serial Port Hardware = yes (I have seen people say both need to be NO. I had to turn on the serial port hardware to make my DVMega modem visible. I guess it depends on your hardware. DVMega needs it. Maybe other hardware doesn't.

Now go to your MMDVM.ini file and make sure display says "Nextion" with no quotes as in the 2nd to last line in the screenshot below.

And that's it. Should work like a champ. Mine does.

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