Notizbl0g.

h4cking, ham radio, fire fighting and m0re

Discard HID Input From CM108 Device

During experimenting with USB soundcard devices based on cm108 chips I discovered that a squelch signal on the GPIO inputs of the sound chip does trigger a keyboard event as if one pressed the “volume down” key. Depending on the system configuration that can lead to your default sound card being muted. In my case I was running UniPager as DAPNET client to the pager network in combination with a self made USB sound device with GPIO-controlled PTT.

If you just want to exlude the emulated volume down key press event you can remap this button press event from the emulated keyboard using an udev hwdb config directive. To achieve this you have to know the keyscan code of the button being emulated. This value can then be remapped or ignored.

Automated Channel Switching With Motorola GM3x0

With the integration of POCSAG/DAPNET features into the MMDVM/MMDVMHost I came to think about if it would be possible to combine an MMDVM repeater/HotSpot with a DAPNET tranmitter. The advantage in Germany is that there is a single coordinated frequency for POCSAG tranmissions on UHF. 439.9875MHz is used for fixed-frequency pagers which are modified to receive on that frequency. With latest hand-programmable pagers (e.g. AlphaPoc) it would basically be possible to set them to the repeater frequency but that wouldn’t work while one is en route.

In the programming software for Motorola GM3x0 radios I found an interesting GPIO setting called “Channel Steering”. Some line of the help function revealed that it would exactly do what I expected. You can trigger a GPIO and the radio switches channels.

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Postmortem Decoding of SSTV/APRS

This years holiday I took my ICOM ID-51 for some portable activities in D-Star. Luckily there also were some announcements of SSTV acitiviy as well as school contacts from the ISS and also a weather balloon start from Minden Germany. As space was limited I had to deal with the radio and my mobile.

SSTV decoding went quite fine using the Android app Robot36. Audio was loosely coupled to the built-in microphone of the mobile. Basically it was just standing a few centimeters besides the mobile.

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NX-5300 Programming

It seems like Kenwood uses totally different terminology to refer to configuration items in their radio programming software. This is my memo for various options that I discovered why program&try :).

I use the radio in NXDN, P25 and DMR modes (and FM as well). Apparently the radio can only use two of the Digital Voice modes at a time. That means you can use P25+DMR or DMR+NXDN or NXDN+P25 in a codeplug but not all three. I you need to switch you have to write another codeplug. Pure FM is always available independantly of the DV modes.

How to Identify a Genuine #MMDVM_HS_Hat

Since DB9MAT an me came up with a selfmade MMDVM_HS board called the MMDVM_HS_Hat there is a number of Chinese copies out there which we belive are bad quality rip-offs. We published our sources under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 (CC-BY-NC-SA 3.0) license which explicitely forbids commercial use (unless authorized by us). Of course these Chinese copies are not authorized and thus just a clone of our work.

To help distinguish between an orginal #MMDVM_HS_Hat and a clone have a look at the two pics below. The first one is an original board revision 1.2 manufactured by us. It has the name “MMDVM_HS_Hat” on it in the upper right part. The silkscreen is properly placed and our callsigns are clearly readable. In addition to that there is the Open Source Hardware (OSHW) logo on the lower left.

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Modification of T-962 Reflow Oven

For the latest MMDVM_HS_Hat project by me and Mathis, DB9MAT I arranged for a reflow oven model T-962 which is a good assistant for SMD soldering work. As per Toufik, F0DEI there were some interesting modifications to make in order to improve the results as well as to get rid of smelly evaporations.

There is a famous article on hackaday (See [1]). It was the reason to open up the unit and get some improvements done. In order to support this there is a nice YT video [2] describing the mods in detail.

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Homemade Data Cable for Yaesu FT-2D

A while ago I bought a Yaesu FT-2D in order to try some YSF with MMDVMs. I discovered that German shops sell the data cable for nearly 90€ which seems quite expensive - especially after discovering that I just contains a pl2303 USB-RS232 adapter and a MAX3232 or similar level coverter. So the only difficulty left to clone this cable was the connector on the radio side. There is a longer thread on Twitter about this (see [1]). Sources for the plug seem to be [2] and [3].

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Excluding FT-232 From Ftdi_sio Driver

For the upcoming AMBEd daemon needed by XLX reflector software there is a need to connect an FTDI USB-serial adapter without using the default ftdi_sio kernel module. Instead the software makes use of the D2XX drivers by FTDI. This driver is available as binary only from FTDI’s website.

The problem with Linux operating systems is that it loads the ftdi_sio driver by default. One option is to blacklist that module. The drawback is that also all other FT232 based USB-serial adapters will also not work anymore. In my case I had some other devices that had to use the ftdi_sio driver while the AMBE device should not. So blacklisting the whole driver is not an option.

Make SVXlink Tell 24h Time / UTC

After re-setting up my SVXlink node I encoutered the problem that the time announced was using German spelling but English time format. That lead to very strange time announcements during the long identification transmission. Also the 24h time format was missing. After reading around on [1] and [2] I found that this can be overridden locally. The best local.tcl settings were found on a German forum (see [2]). Andi, DL1HRC made a nice local.tcl that just needs to be installed under /usr/share/svxlink/events.d/local. The sub directory has to be created if not existent. So the last issue was to let listeners know that the time ist UTC.

Interfacing Motorola GM1200

I had an unused GM1200 that should be interfaced to a SVXlink node. Turns out that it is not as easy as I thought. I wanted to use the CTCSS decoder and a hardware squelch signal. The CPS offers different options that can be programmed per FM channel. The essence is the option “Data Channel”. That enabled unfiltered raw output on pin 25 of the accessory connector. The audio input can be connected to pin 24. The hardware squelch can be used on pin 8. It carries +4.5V if the squelch is closed and drops to GND if the squelch opens.

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