USING GPIO PINS TO KEY RADIO PTT VIA A HOMEBREW OPTO COUPLER (4N25) BOARD WITH THE RASPBERRY PI 3 B VER 1.2
This short manual discuss the method using the GPIO pins on the Rpi.
to indicate TX / RX LED status on a AllStar Node
to key PTT via opto coupler board on a AllStar Node.
Warning: Ensure that you connect the LED’s to the correct pins. The GPIO pins are 3.3 volts maximum and output pins have a limited current capability of 16 mA. When interfacing be aware of this because you can damage the PI if you exceed the ratings!! I am not responsible if you damage or destroy your Raspberry Pi!!
I use a 4N25 Opto Coupler, 1 Resistor and 1 Capacitor on Veroboard. I would however add a BAT43 Diode as further protection to the circuit. See image below.
I highlighted the changes in black for keying the homebrew PCB circuit using the GPIO pins.
Go to and open MobaXterm
Check to see if the rc.allstar file is in /usr/local/etc/
cd /usr/local/etc
enter
ls or dir
enter
sudo nano rc.allstar
enter
File will open. Add bold typed info as listed below.
#########################################
#!/bin/bash
#
# This is the startup rc script for allstar asterisk
#
# Rather than changing anything here
# please use the /usr/local/etc/allstar.env file
# for configuration changes.
#Makes gpio pins go to output upon startup
/etc/asterisk/local/write_gpio.sh
# If root profile missing, replace it.
if [ ! -f /root/.bash_profile ] ; then
/usr/bin/cp -f /etc/.bash_profile.backup /root/.bash_profile
fi
# source the allstar variables
if [ -f /usr/local/etc/allstar.env ] ; then
. /usr/local/etc/allstar.env
else
echo " Unable to read /usr/local/etc/allstar.env file."
echo " Asterisk will not start"
exit 1
################################################
Once the bold info is entered
save
ctrl + x
yes
cd
enter
cd /etc/asterisk/local/
enter
sudo nano write_gpio.sh
then type the following script
####################################
#!/bin/bash
#script name - write_gpio
gpio mode 7 out ; makes gpio 7 pin 7 an output
gpio mode 2 out ; makes gpio 2 pin 13 an output
gpio mode 4 out ; makes gpio 4 pin 16 an output
#####################################
(Real Pin 7 = COS or RX node receiving voice from the Internet.)
(Real Pin 13 = TX or PTT node transmitting your voice into the Internet.)
(Real Pin 16 = PTT radio using 4N25 Optocoupler to key your radio transmitter.)
save
ctrl x yes enter
Check if write_gpio.sh file was created using ls enter or dir enter
Make write_gpio.sh file executable
chmod +x write_gpio.sh
cd
cd /etc/asterisk
enter
sudo nano rpt.conf
Under “Events” add the following:
########################################
; EVENTS
[events467652]
sudo /usr/local/sbin/7high.sh = s|t|RPT_TXKEYED
sudo /usr/local/sbin/7low.sh = s|f|RPT_TXKEYED
sudo /usr/local/sbin/2high.sh = s|t|RPT_RXKEYED
sudo /usr/local/sbin/2low.sh = s|f|RPT_RXKEYED
sudo /usr/local/sbin/4high.sh = s|t|RPT_TXKEYED
sudo /usr/local/sbin/4low.sh = s|f|RPT_TXKEYED
; Commands for FOB COS indicator when available
; For this to work you must also add - gpio4 = out,0 - to simpleusb.conf
; Uncomment (remove ;) on next two lines to activate
;cop,62,GPIO4:1 = c|t|RPT_RXKEYED
;cop,62,GPIO4:0 = c|f|RPT_RXKEYED
[events1999]
; FUNCTIONS
##########################################
save
ctrl x
Yes
enter
cd
cd /usr/local/sbin/
enter
Create 6 script files (Example: sudo nano 7high.sh enter)
7high.sh
7low.sh
2high.sh
2low.sh
4high.sh
4low.sh
In each script put:
7high.sh
#################
#!/bin/bash
gpio write 7 1
#################
7low.sh
#################
#!/bin/bash
gpio write 7 0
#################
2high.sh
#################
#!/bin/bash
gpio write 2 1
#################
2low.sh
#################
#!/bin/bash
gpio write 2 0
#################
4high.sh
#################
#!/bin/bash
gpio write 4 1
#################
4low.sh
#################
#!/bin/bash
gpio write 4 0
#################
save each one
ctrl x
Yes
enter
still in cd /usr/local/sbin/
make all 4 executable using the command
sudo chmod +x /usr/local/sbin/xxxxxx.sh
chmod +x 7high.sh
chmod +x 7low.sh
chmod +x 2high.sh
chmod +x 2low.sh
chmod +x 4high.sh
chmod +x 4low.sh
cd
sudo reboot
TX / RX LED’s and 4N25 Optocoupler PTT will now be working!!
Note: The one LED will light to show that the radioless node is receiving voice from the Internet. The other LED will light to show that the radioless node is transmitting your voice into the Internet. The TX LED on your radio will light-up to indicate that the PTT is active.
Download Manual HERE (PDF)
Recognition:
AllStarLink Discussion Groups
HamVoip
Manual compiled by:
Johan Terblanche ZS1I
Mossel Bay
Date: 24 February 2024
GPIO
outlay diagram and photos related to the Raspberry Pi 3 B Ver 1.2
below:
