By akh, a month ago
APRS is a tactical digital communications system used between amateurs radio, to exchange positions & messages, here I blog my experience decoding/encoding APRS with a small Arduino as it may help some of you too.
Some transceivers are incorporating this functionalities but most of them don't, a lot of new technicians start with cheap Baofeng radios (30$) which don't provide advanced functionnalities but here is a way to solve that.
I've first looked at Bertos project, a realtime os for micro controllers as Atmel 328p (Arduinos), you can see my 1st attempt there:
This was the receiver only, a simple divider, the "hard" part was to understand the Baofeng/Kenwood mic jacks.
It takes me a long time to figure out that the Baofeng was too slow to trigger the squelch, so the Arduino missed the beginning of the message, hopefully I have a Kenwood too ...
So for a Baofeng using this kind of APRS decoder, you have to disable the squelsh completly, and set the volume very high it has to reach a proper signal on the arduino around -3v/+3v.
For the AFSK modulation, the Bertos project use a DAC made with 4 resistors.
Later, I've discovered the wonderful work of Mark Qvist MicroAPRS, mostly the same circuit as the Bertos project but with an awesome documentation of the code, it's a pleasure to read & learn.
So I've started to work on a circuit using a Bluno Nano an Arduino Nano with Bluetooth Low Energy, as an iPhone developer, this piece of electronics is just incredible and gives me the capabilites to connect my circuits to iphone Apps.
It's working but hardly a mobile solution :)
I'm currently designing a PCB for that.
I'm using Frizting to design and then export to OSHPark for the PCB manufacturing, it's far from perfect but I will improve the circuit and publish it soon !
This plus an iPhone app and you'll rock APRS !
73 de KK6NXK
By akh, 2 months ago
hamradio radio radio amateur
When I was a young child, I remember listening to an old radio receiver with my grandfather, looking for morse transmission.
30 years later, I take the opportunity to get my radio amateur license in the US, it was not difficult (Technicial license is easy), especially cause US radio amateurs are using the metric system (almost all the time ...), the only difficulties were to learn some terms and simple formulas from french to english and to know some parts of regulation by heart (I have never been able to learn by heart).
A lot of people keep asking me why are you doing this? Do you want to speak to a microphone to a stranger?
First why not, it's not the craziest thing I've ever done :)
Then they probably have forgotten that every single piece of technology today are using radio waves, from your 4G phone to wifi to Bluetooth, learning and understanding that is really useful.
For example Radio amateur bands overlap some of the "civil" bands, it gives some extended privileges to a radio amateur to experiment with long distance wifi transmissions.
So it's not just about voice but data too.
Another aspect is electronic, a lot of radio amateur are sharing hardware and electronic circuits to build your own receiver/transceiver, before it was cool on the Internet.
Learning electronic to build something real is a lot more rewarding than it was at school...
Even without a license this is a brand new world to explore, receiving satellite images of the Earth is one of the many possibilities you can get entering radio world.
This is the beginning of a new knowledge branch to conquer !
See my work on an APRS bluetooth Modem
73 de KK6NXK
By the way in french it's radio amateur and not amateur radio :)
By akh, 6 months ago
FreeBSD 10 is out and it's time to replace your Linux boxes
SC gen 2 is a VIA U2250 with 2Gb memory.
Start the rescue shell in amd64 12.04 Ubuntu, connect to the box via SSH with the temporary password
apt-get install qemu-kvm
sudo qemu-system-x86_64 -no-kvm -hda /dev/sda -cdrom ./FreeBSD-10.0-STABLE-amd64-20140216-r261948-disc1.iso -net nic,model=e1000 -vnc :1,yourpassword -boot d
This install qemu and run the FreeBSD installer from the downloaded CD.
Run a VNC client on your computer and connect to your dedibox ip, you should watch FreeBSD boot from the CDROM.
Complete a normal installation, at the end it will ask if you want to run a shell answer is YES and then type this to reinstall the bootloader.
If you are using UFS (default)
fdisk -B -b /boot/boot0 /dev/ada0
If you are using ZFS:
gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada0
Type exit and reboot to the normal mode.
Happy FreeBSD !
By akh, 7 months ago
FreeBSD images for arm are now built from the FreeBSD Foundation ! So it's an easy process to get it on your Pi.
Download your image from the ftp repository
Insert a 4Gb or more SD card in your PC and copy the FreeBSD image into it, here are the commands for a Mac:
sudo diskutil list
sudo diskutil unmountDisk /dev/disk1
sudo dd if=/Users/akh/Downloads/FreeBSD-10.0-STABLE-arm-armv6-RPI-B-20140127-r261200.img of=/dev/rdisk1 bs=1m
sudo diskutil eject /dev/disk1
Boot your pi with the card and welcome to FreeBSD !
If you are using the wifi dongle from Adafruit this may help:
echo legal.realtek.license_ack=1 >> /boot/loader.conf
echo wlans_urtwn0="wlan0" >> /etc/rc.conf
echo ifconfig_wlan0="wpa DHCP" >> /etc/rc.conf
And set your wifi password with wpa_passphrase
wpa_passphrase yourssid yourwifipassword >> /etc/wpa_supplicant.conf
By akh, 1 year, 3 months ago
As an iphone developer contractor, I've released some applications on the Apple Store for my customers but not on my own.
I've spent 20 hours on website release, marketing, 3D for the human trainer and application design, and last 10 hours to create the app and release it to Apple ...
It's a free app and available on the Apple Store, have fun.
My next personal project will be a game, stay tuned ;)