Building a SHARI AllStarLink Node
After having built an AllStarLink node for stationary operation in the past, I decided to build a second node for mobile operation. It should be simple, inexpensive and relatively compact. Furthermore, a power supply via USB (5V DC) was a prerequisite for this project.
The choice fell on the inexpensive SHARI hats, which are based on the well-known SA818 module (hence SHARI, which stands for "SA818 Ham Allstar Radio Interface"). These can be purchased directly from China for about 55€.
Ready built, the node looks like this:
Additionally I ordered a SMD LFCN-490+ low pass filter, since the SHARI hats are known to generate not very clean emissions. I found this very good wiki page that describes how to add this kind of LPF to the SHARI: wiki.fm-funknetz.de / archive.org.
The following picture shows the naked SHARI board in unmodified state:
After opening the case, I've removed some of the protective coating between the antenna port and the SA818 module. Then I've cut a larger portion of the trace with a sharp knife:
Everything was now prepared for soldering the LPF to the PCB. Please note that the component must be placed lengthwise to the disconnected trace and the side pads of the LPF must be soldered to GND:
After this mod has been done, I've reassembled the SHARI hat and connected it to a Raspberry Pi 3 with both USB connectors. It is very important to initially connect both since one is for the USB sound card and the other one to program the SA818. During later operation, only one USB port needs to be connected.
I've then performed the following steps to install and configure ASL:
- download the latest ASL 2.0.0 beta image from here: http://downloads.allstarlink.org/ASL_Images_Beta/Raspberry_Pi2_3_4/
- flash the image to a micro SD card
- connect the Raspberry Pi to your local network
- boot the pi
- SSH to the dynamically assigned IP address and port 222 (user: repeater, pass: allstarlink)
- become root (sudo su -)
- update the Linux installation:
- curl -s http://apt.allstarlink.org/repos/repo_signing.key | apt-key add
- apt update --allow-releaseinfo-change
- apt dist-upgrade
- install some libraries that are needed for programming the SA8181
- apt-get install python3-dev python3-pip
- pip3 install pyserial
- download the SA818 programming script from https://wiki.fm-funknetz.de/doku.php?id=fm-funknetz:technik:shari-sa818
- save the script as ~/sa818-running.py
- chmod u+x ~/sa818-running.py
- use your favorite editor to adapt the script to your needs (frequency, CTCSS tones)
- execute the script: ./sa818-running.py
- execute the tool asl-menu to configure your node
- go through the menus and configure your node, start with "Run first-time menu". Follow the instructions and enter your node number etc.
- register the node at the AllStarLink website
- enable the simple usb module by uncommenting "rxchannel=SimpleUSB/usb" in /etc/asterisk/rpt.conf
Apart from the usb soundcard settings, the node should now be functional, e.g. able to connect to other nodes. To configure the integrated soundcard of the SHARI, the file /etc/asterisk/simpleusb.conf has to be modified as follows:
; SimpleUSB configuration
[general]
[usb_562491]
eeprom = 0
hdwtype = 0
rxboost = 0
carrierfrom = usbinvert
ctcssfrom = no
invertptt = 1
deemphasis = yes
plfilter = no
rxondelay = 5
rxaudiodelay = 10
txmixa = voice
txmixb = no
txboost = 0
invertptt = 0
preemphasis = yes
duplex = 0
As a last step, audio levels need to ajusted with the tool simpleusb-tune-menu