An interface and keypad emulator for Digital Security Control's PC1550 Alarm Panel
This class is a keypad emulator for the Digital Security Control's (DSC) PC1550. The model number of the keypad it emulates is PC1550RK. It should work with any ATmega chipset, and was tested using an Arduino UNO.
With this programmatic interface, you could emulate your own keypad on the device (iPhone maybe?) of your choice. Or you could setup your own monitoring/alerting system (maybe send yourself a text message) when certain alarm events occur.
There are four wires that go to the keypad:
Voltage. This should be about 12V. On my system, a
voltage meter read 13.3V with a brand new battery. You
should be able to safely use this as a power supply for the
Arduino. Simply connect the red line to the pin labeled Vin.
The Arduino's internal voltage regulator will take care
of the rest. Because the PC1550 has a backup battery
supply, your Arduino will continue to be powered even
when the electrity goes out (quite convenient).
Ground. If you're using the PC1550 to supply power to
the Arduino, connect this to the GND pin next to the Vin pin
Clock. The PC1550 control panel determines the clock cycle.
So long as the processClockCycle() method on this class is
called more frequently than half a clock cycle from the PC1550
then we will safely be able to read and write signals from
the PC1550 control panel. The total cycle is about 1500-1600
micro-seconds, on average (roughly 650 Hz). Because data
is sent when the clock is low and read when the clock is high,
we must run the processClockCycle() method at least every
800 micro-seconds. The more frequently the processClockCycle
method is called, the more likely data transmission will
succeed (in both directions) without data loss. If you're
not sure if you can commit to a calling the processClockCycle()
function frequently enough, then you can use
processTransmissionCycle() instead which will call
processClockCycle() and block until a full transmission cycle
is complete. This could be handy if your program is performing
another task that could use significant clock cycles between
calls to processClockCycle(). On the downside,
processTransmissionCycle() takes between 57ms and 104ms to
complete.
Connect the clock line up to either a digital or analog pin.
We only read on this line using digitalRead, so either a
digital or analog pin will do. Analog PIN 4 is the default
but can be overriden via the constructor to this class.
Data. The data line is used to send bits to and from the
PC1550 when the clock is low and high, respectively.
Connect this line to any analog pin. While we can read
data from the panel using only digital functions, we
must use analog functions to pull the pin low when we
want to send data back to the control panel. Analog pin 3
is the default but can be overridden via the contructor.
There is one additional connection that can be made that can provide additinal state information from the alarm controller.
PGM. The PGM terminal on the DSC PC1550 control panel
can be programmed to do a number of things. One option
is to configure it as a 2nd data line. The installation
manual refers to the PC16-OUT module. This module reads
data from the PGM line and we can emulate that module here.
This line does not go to the keypad, and is optional for
use by this library.
For the PGM terminal to work, it will need to be connected to the
AUX+ terminal with a 1k Ohm resistor (for PC1550s)
See http://www.alarmhow.net/manuals/DSC/Modules/Output%20Modules/PC16-OUT.PDF for a full listing of PGM options.
The PC1550 control panel starts by holding the clock high for roughly 26.5ms. It then clocks out 16 cycles (one cycle is represented by the clock going low and then returning to a high state). After 16 clock cycles, the PC1550 holds the clock high for roughly 26.5ms again, which starts the entire cycle over.
During the 16 clock cycles data is received when the clock is high:
-
The first 8 clock cycles are used to send one octet (byte) of data to the keypad (one bit per clock cycle). This byte contains information about which zones are currently open (what zone lights should display on the keypad). For this reason, the first 8 bits are referred to here as "zone bits."
The table below shows how the data is received and interpretted. Bit 7 is received first, and bit 0 is recieved last. When bit 7 is on, then the zone 1 light should be on; when bit 6 is on, then the zone 2 light should be on, etc. Bits 1 and 0 are not used.
Zone Bit 7 6 5 4 3 2 1 0 Zone 1 2 3 4 5 6 (Not Used) -
The second 8 clock cycles send 8 more bits. This byte contains information about the other lights that should be enabled on the keypad. These bits represent other states and therefore, these bits are referred to here as "state bits."
The table below shows how each bit is used. Note that when bit 0 is on, the keypad beep emits a short beep.
State Bit 7 6 5 4 3 2 1 0 Ready Armed Memory Bypass Trouble X X Beep
Between receipt of the zone bits, data can be sent back to the control panel when the clock is low. In other words, the panel sends out its bits when the clock is high and the keypad sends back its data when the clock is low.
The keypad only sends back 7 bits-- one bit between each of the 8 zone bits received. These bits represent a button press. When taking the keypad as a table (rows and columns) of buttons, the first three bits received represent the column of the button pressed. The last four bits represent the row of the button pressed:
First Three Bits Last 4 Bits
Column 1 100 Row 1 0001
Column 2 010 Row 2 0010
Column 3 001 Row 3 0100
Row 4 1000
Row 5 0000
No Key 000 0000
Encoding bits in the data line: When the data line is LOW the corresponding bit should be ON. When the data line is HIGH the corresponding bit should be OFF.
If the PGM line is connected, then 16 more bits of data are received on this line if (and ONLY IF) the PGM line is configured in PC-16OUT mode. Refer to the PC1550 installation manual for instructions on how to configure this mode. The bits meaning follow:
- 0 -- PGM Output (whatever the PGM is configured for) ... (This library assumes PGM terminal has been programmed for ... strobe output. This sets bit 0 to the on position ... when the alarm goes off. And the bit remains set until ... the panel is disarmed).
- 1 -- Fire buttom pressed (on for 4 sec)
- 2 -- Aux button pressed (on for 4 sec)
- 3 -- Panic button pressed (on for 4 sec)
- 4 -- Armed
- 5 -- Armed
- 6 -- Armed with bypass (on for 5 sec)
- 7 -- Trouble
- 8 -- Fire (on when fire alarm is latched in)
- 9 -- Not used
- 10 -- Zone 6 tripped while armed
- 11 -- Zone 5 tripped while armed
- 12 -- Zone 4 tripped while armed
- 13 -- Zone 3 tripped while armed
- 14 -- Zone 2 tripped while armed
- 15 -- Zone 1 tripped while armed
For the PGM terminal to work, it will need to be connected to the AUX+ terminal with a 1k Ohm resistor (for PC1550s)
To use the library, simply do three things:
(1) Include PC1550.h in your Arduino program
(2) Instantiate an instance of the PC1550 instance
(3) call processTransmissionCycle() on the object in each loop
The PC1550 object has a number of methods you may call to determine the state of the lights on the keypad. All the following methods return a boolean value:
ReadyLight() -- Indicates whether the keypad's ready light is on
ArmedLight() -- Indicates whether the keypad's armed light is on
MemoryLight() -- Indicates whether the keypad's memory light is on
BypassLight() -- Indicates whether the keypad's bypass light is on
TroubleLight() -- Indicates whether the keypad's trouble light is on
Zone1Light() -- Indicates whether the keypad's zone 1 light is on
Zone2Light() -- Indicates whether the keypad's zone 2 light is on
Zone3Light() -- Indicates whether the keypad's zone 3 light is on
Zone4Light() -- Indicates whether the keypad's zone 4 light is on
Zone5Light() -- Indicates whether the keypad's zone 5 light is on
Zone6Light() -- Indicates whether the keypad's zone 6 light is on
Beep() -- Indicates whether the keypad is beeping
The PC1550 object has a number of methods you may call to determine the state of the alarm based on the PGM output terminal. All the following methods return a boolean value:
PGMOutput() -- Indicates the programmable PGMOuput bit is set
fireButtonTripped() -- Indicates the fire button on the keypad caused
the fire alert to be tripped
auxButtonTripped() -- Indicates the aux button on the keypad caused
the aux alert to be tripped
panicButtonTripped() -- Indicates the panic button on the keypad caused
the panic alert to be tripped
systemArmed() -- Indicates the system is currently armed
armedWithBypass() -- Indicates the system is armed in bypass mode
systemTrouble() -- Indicates a trouble situation. Use the
keypad light methods to deduce the actual
problem
fireAlarmTripped() -- Indicates the fire alarm has been tripped
AlarmTripped() -- Indicaets the security alarm has been tripped
Zone1Tripped() -- Indicates Zone1 tripped since system was armed
Zone2Tripped() -- Indicates Zone2 tripped since system was armed
Zone3Tripped() -- Indicates Zone3 tripped since system was armed
Zone4Tripped() -- Indicates Zone4 tripped since system was armed
Zone5Tripped() -- Indicates Zone5 tripped since system was armed
Zone6Tripped() -- Indicates Zone6 tripped since system was armed
keypadStateChanged() -- Indicates the state of the keypad has changed
since the last call to processTransmissionCycle()
There are a number of misc methods to provide additional details on the state of the system:
consecutiveBeeps() -- The number of clock cycles where a beep has
sounded from the keypad
consecutiveKeyPresses() -- The number of clock cycles where the same
key has been pressed (and held down)
atTransmissionEnd() -- Indicates a full transmission (across 16
clock cycles) has been read from the panel
readyforKeyPress() -- Indicates the panel is ready for the next
keypress
You can simluate a keypress with the following method:
bool sendKey(char c, int holdCycles)
where
char is the character to send. Valid values are
'1' through '9',
'#'
'*'
'F','A', and 'P'
holdCycles is the number of cycles across which to simulate
holding of the key
returns false if the panel is not ready for a keypress or
if the character code is not valid.
To read from the panel, call one of the following methods:
processTransmissionCycle() -- blocks until a full transmission has
been read across 16 clock cycles
processClockCycle() -- reads a single clock cycle and release
control so that you may perform other
tasks before the next clock cycle. You
must call this method every 800us or
data receipt will not be reliable. If
you are unsure, call
processTransmissionCycle() instead.
#include <PC1550.h>
PC1550 alarm = PC1550();
void setup() {
Serial.begin(115200);
}
void loop() {
//process a full transmisison cycle with the PC1550 controller
alarm.processTransmissionCycle();
//print the state of the keypad and and PGM output to the Serial console
if (alarm.keypadStateChanged())
printState();
}
void printState(){
Serial.print("\n|");
alarm.ReadyLight() ? Serial.print("R") : Serial.print(" ");
alarm.ArmedLight() ? Serial.print("A") : Serial.print(" ");
alarm.MemoryLight() ? Serial.print("M") : Serial.print(" ");
alarm.BypassLight() ? Serial.print("B") : Serial.print(" ");
alarm.TroubleLight() ? Serial.print("T|") : Serial.print(" |");
alarm.Zone1Light() ? Serial.print("1") : Serial.print(" ");
alarm.Zone2Light() ? Serial.print("2") : Serial.print(" ");
alarm.Zone3Light() ? Serial.print("3") : Serial.print(" ");
alarm.Zone4Light() ? Serial.print("4") : Serial.print(" ");
alarm.Zone5Light() ? Serial.print("5") : Serial.print(" ");
alarm.Zone6Light() ? Serial.print("6|") : Serial.print(" |");
alarm.Beep() ? Serial.print("B| ") : Serial.print(" | ");
alarm.fireButtonTripped() ? Serial.print("F"):Serial.print(" ");
alarm.auxButtonTripped() ? Serial.print("A"):Serial.print(" ");
alarm.panicButtonTripped() ? Serial.print("P|"):Serial.print(" |");
alarm.systemArmed() ? Serial.print("Armed |") : Serial.print("Disarmed|");
alarm.Zone1Tripped() ? Serial.print("1") : Serial.print(" ");
alarm.Zone2Tripped() ? Serial.print("2") : Serial.print(" ");
alarm.Zone3Tripped() ? Serial.print("3") : Serial.print(" ");
alarm.Zone4Tripped() ? Serial.print("4") : Serial.print(" ");
alarm.Zone5Tripped() ? Serial.print("5") : Serial.print(" ");
alarm.Zone6Tripped() ? Serial.print("6") : Serial.print(" ");
alarm.AlarmTripped() ? Serial.print("|A|") : Serial.print("| |");
}