The "Cockscomb" Repeater is undergoing major rework to add two UHF
links, one UHF APRS digipeater and a WiFi base station to possibly serve the
isolated community that has hosted this repeater for so many years.
The controller has been developed from scratch, thanks to the pioneering development done by Allan, ZS2R
New Controller Schematic:
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PEARS REPEATER CONTROLLER
(Compiled
by ZS2R)
History
This
project was born out of the need to replace existing CMOS logic used, with
ageing 24 volt Storno equipment, on the East Cape Repeater Network.
This controller is PIC based
and will be more versatile and can be updated and reprogrammed as the need
arises. A facility needed in the changing technological environment. The need
was highlighted by Chris Scarr,ZS2AAW, and implemented by Allan Whitehead, ZS2R.
Chris provided all the details required of the controller and most have been
accommodated. His many years of experience with repeaters has ensured a good
working system - the best in
OVERVIEW
The
unit has been based on the PIC 16F685 microcontroller and the MC145436 DTMF
receiver. Remote communication with
the unit is by DTMF code (full 16 character code). Responses from the unit are
by Morse Code, alarm tones and other tones.
The unit has the following inputs on one plug,
that doubles as a serial programming port for the PIC :- door alarm,
mains alarm, analogue port, Vcc and gnd. Removing this plug and plugging in the
in circuit serial programmer allows the PIC to be reprogrammed in position with
all other peripherals attached.
In
addition the following are provided for:- an audio output, a PTT controller and
a busy line monitor. There are 6 control channels that can be
interrogated and switched on/off remotely. An analogue to digital converter is
also available as a 0 to 30 voltmeter or as a remote thermometer. On
interrogation the unit will send a CW message indicating the potential
difference in volts, to the nearest 0.2 volts or the temperature in degrees
Celcius.
Each
control channel and each alarm port can be simply programmed to have a five
character identity (ID) code. These codes cannot be remotely changed. A link
needs to be inserted on the board to facilitate code programming. Should the
board lose power, the current states of all control channels and alarms are
retained in the EEPROM and will be restored on power up. The channels or alarms
can be remotely locked on or off by the system manager using the unique code
programmed at initialisation.
If
more than 6 control channels are required another unit can be placed in
parallel. Each channel would have its own ID code.
SOFTWARE
All
software has been written in assembler and the author has attempted to keep it
simple, so that others might later easily modify the code.
The
full program is on the accompanying CD
as “repeater controllerV2.asm"
No
attempt has been made to minimize the program memory used so
the program contains a lot of simple routines repeated for each channel.
Of special note to any person wishing to modify code is the fact that the 16F685 has 4k program memory, which is divided into two pages. Whenever a page is crossed the necessary page bits must be set or cleared. I used the" pagesel" instruction in MPLABASM to do the necessary.
OPERATION
DETAILS
The
unit's six control channels can be remotely controlled by DTMF signalling. Each
channel has a unique five character code. By sending the code followed by a *
the channel can be switched on, while the code followed by a # will switch the
channel off. By sending the code only, the status of the channel will be sent
back by the unit. One long beep is sent to indicate the channel is switched on
and a number of short beeps to indicate it is off. This convention is used
through out.
The
door alarm latches on when pin 19 goes low, if positive logic is set or when pin
19 goes high if negative logic is set. The alarm will sound as soon as possible
and again every 20 minutes. The state of the busy line is ignored. The alarm
sound will be an emergency fire engine alarm
followed by a CW message of the alarm's ID code. The status of the alarm
can be checked at any stage by
sending the alarm's ID code only. Alarm sounding can be turned on/off by sending
the code plus * to turn on or # to turn off. Software latches the alarm. The
latch can only be removed by switching the alarm off. The alarm will latch but
not sound if it is turned off. Interrogation of the alarm, by sending the ID
code only, will reveal whether it has latched on or not since having been turned
off. To remove the latch the alarm must be turned off (even if it is off !) or
the unit must be reset.
The
analogue port is used as a 0 to 30 voltmeter. The potential on the pin must be
between 0 and 5 V, so the external circuit must provide the necessary
attenuation, low pass filter and calibration facilities. When the temperature
mode is selected the potential on the pin must again be between 0 and 5 V and
the unit will respond with a temperature value between 0ºC and 50ºC. The port
has a unique programmable five digit code. If this code is sent the unit will
respond with a CW message indicating the potential difference in volts followed
by a V, or the temperature in C as programmed during setup.
The * and # characters after the code will be ignored in this case.
The
mains alarm is sounded when pin 18 is pulled low (or high for negative logic)
and again after 20 minutes, should the condition prevail. Software does not
latch this alarm. Should pin18 go high (low for negative logic) and low (high
for negative logic) again the alarm will resound immediately. The alarm can be
turned off by sending its ID code plus # and on by sending it's code plus *.
Since the alarm will sound every 20 minutes the status
can be interrogated by sending the DTMF ID code only, at any time. The
alarm sound will be bee - baa repeated 5 times followed by a CW message of the
alarm's status and id code. If the alarm is turned on and the mains is
re-established a CW message "mains on” & alarm's ID will be sent.
The
system manager can lock or unlock any port or alarm by sending his programmable
4 character code and the port or
alarm reference number as the fifth character and a * to lock or # to unlock the
port or alarm. Once a port or alarm is locked it cannot be switched by normal
methods. To revert to normal operation it must be unlocked.
The
busy line is checked (and debounced) before
every transmission except for the
alarms. If the line is low the unit will wait a maximum of 2.5 minutes for the
line to go high. If the busy line is low for longer than 2.5 minutes the
transmission will be abandoned. In the case of an interrogation of a channel
while the busy line is low (in TX) the controller will wait for 1.25 minutes
then send a CW message "PSE QRT"
(please stop transmitting) wait
until the busy line goes high, then send the status report. Should the
busy line remain low for a further 1.25 minutes, a status message will be sent,
regardless of the busy line status. The unit will respond to the first DTMF
signal sent (e.g. switch on/off or interrogate)
immediately, but to no others
during this waiting period of maximum length 2.5 minutes.
For
all transmissions the PTT is set then a delay of one second is applied before
the transmission begins.
The
only way to reset the device is to power down and power up again.
PROGRAMMING
(or initiallising)
The
logic levels for the ports are as follows:-
When
any of the ports are switched on the corresponding output will go high. This is
called positive logic. If an opposite level is required on any of the ports then
the logic must be set to negative as indicated below (# after the 5 ID
characters).
The
logic levels for the alarms are as follows:-
The
alarms are normally triggered when the appropriate pin goes low. If it is
required that the alarm trigger when the pin goes high, negative logic must be
set on that alarm as indicated below (# after the 5 id characters).
When
initially programmed, the ports and alarms will have the following codes and
reference numbers.
PORT
REFERENCE NUMBER
DTMF CODE
1
1
10001
2
2
20002
3
3
30003
4
4
40004
5
5
50005
6
6
60006
door
alarm
7
70007
analogue
8
80008
mains
alarm
9
90009
system
manager 0
0000 only 4 zero's
The
reference numbers are embedded in code and cannot be changed except by changing
the device's code.
To
program a new code for a port, the steps 1 to 7 must be followed precisely.
(1)
set the link on the circuit board to pull RC7
(pin 9) low.
(2)
enter the port reference number (0
to 9)
via DTMF. A successful and valid entry
will cause the channel LED
of the appropriate port to flash at freq. 2 Hz. for 3 seconds. In the
case of the door alarm LED’s for channel 1&2 will flash together. For the
analogue port LED’s 3&4 will flash together, for the mains alarm LED’s
5&6 will flash and for the system manager all six LED’s will flash .
(3)
wait for the flashing to stop.
(4)
Now enter the new 5 character code for the port or alarm, followed by a # if
negative logic on this port or alarm is required. A
4 character code is entered for
the system manager. Any of the 16 DTMF characters may be used. A successful and
valid entry will cause the appropriate LED’s to flash continuously. In the
case of the analogue port, enter the new 5 character code followed by a # if
temperature in degrees Celcius is to be sent , else a voltmeter reading in volts
will be sent by default.
(5)
remove the link on the circuit board
once the port LED’s start
flashing. The LED's will stop flashing when the link is removed.
(6)
test the new code by setting the port on and
off.
(7)
set the port, channel or alarm on or off as required.
No
channels, ports or alarms must be given the same ID code.
During
the initial programming it might be best to unplug the ports 1 to 6 as they
would be pulsed when the LED’s flash.
There
is a jumper that can be removed to turn the LED's off
Special
Versions
Cockscomb
Controller.
The
mains alarm has been changed in the following way.
1)
An A to D converter has been configured on the alarm pin, pin 18.
2)
Software monitors the voltage and sends an alarm and message, "battery
low", when the voltage drops below 2.04V. If the voltage rises above 2.3V
the alarm and message is cancelled. If the voltage drops below 1.94V an alarm
and message, "load disconnect imminent", is sent The alarm and message
will be cleared when the voltage rises above 2.3V. Should the voltage drop below
1.9V all six control channels will be disconnected,
due consideration being made for each channel that might have been set
for negative logic. If a channel is disconnected, it will remain so.
A reconnect is made when the voltage rises above 2.3V and will restore
the conditions prevailing before the disconnect.
The
alarm will resound after 20 minutes and send a message indicating the voltage
level at that time. The messages "battery low, "load disconnect
imminent" or no message if the voltage is between 2.04V and 2.3V at that
time.
The
alarm can be interrogated at any time and messages as above will be sent.
3)
If the alarm is turned off, ID code #, software will still operate as above but
no messages will be sent.
4)
If a load disconnect has occurred, individual channels can still be switched as
usual.
5)
A load disconnect will override any system manager locks, but the locks will be
reapplied when a reconnect occurs.
6)
The analogue port, pin 3, must be programmed by the user to match the hardware
connected to the pin. Voltage 0 - 28.3V or temperature 0 - 50 C. Due
consideration for the connection to an A to D converter must be taken. The 5V
supply is used as a reference and should be as stable as possible. Noise on the
input pin should be considered. The signal source must have an internal
impedance less than 10k. See note on A to D input.
Note
on A to D input
For
the ADC to meet its specified accuracy, the charge holding capacitor (CHOLD)
must be allowed to fully charge to the input channel voltage level. The source
impedance (RS) and the internal sampling switch (RSS) impedance directly affect
the time required to charge the capacitor CHOLD. The sampling switch (RSS)
impedance varies over the device voltage (VDD), The maximum recommended
impedance for analog sources is 10 kΩ. As the source impedance is
decreased, the acquisition time may be decreased. After the analog input channel
is selected (or changed), an A/D acquisition must be done before the conversion
can be started. To calculate the minimum acquisition time, consult the PIC16F685
data sheet.
20/11/2010
