Alarm Script Recipes

LinkMeter on the RaspberryPi has the ability to fire off user scripts when an alarm goes off. This is in addition to beeping the piezo buzzer. This requires some degree of Linux shell scripting expertise, but using some of these recipes might make things a little easier to understand.

A Note About Alarm Arming

To prevent alarms from turning on and off every time the temperature bounces back and forth across the alarm point there is a hysteresis. This means that the temperature must be outside of the alarm range by more than 1 degree before the alarm will "arm" and be capable of sounding.

Example: Your current temperature is 99.9, and you set the high alarm for 100 at this time. Your alarm is not armed yet and will not arm until is is a degree from the alarm threshold, that is below 99, say 98.9. Even if the temperature rises to 500 the alarm will not go off, as it was never armed.

Now assume the current temperature is 98.9, and you set the high alarm for 100. When it hits 100, the alarm will fire. Even if it drops back below 100, it will keep ringing until silenced. Silencing the alarm only silences the alarm. If the temperature drops below 99 again, the alarm will rearm, and then goes back over 100, the alarm fires again.

Action	Will Ring Again?	Must Re-Arm?
Press any button on HeaterMeter unit	Yes	Yes
Unplug the alarming probe	Yes	Yes
Clicking 'Silence' on web popup	Yes	Yes
Setting the trigger point to 0 with al_set	Yes	Yes
Open the lid until lid detect activates	Yes	No
Un-ticking Alarm 'On' in web config page	No	Yes
Setting the trigger point negative with al_set	No	Yes
Alarm Action = Silence	Yes	Yes
Alarm Action = Disable	No	Yes

Editing Scripts

Via Web

From the LinkMeter configuration website navigate to LinkMeter -> Alarm Scripts. Each script has its own reset / save button! Do not try to edit multiple scripts without saving each in between. The script will only run if the "Execute on alarm" box is checked at the time the alarm goes off (currently ringing alarms have no effect).

Manually

First of all, alarm scripts are located in /usr/share/linkmeter/. Do not edit the script named "alarm", as this file will be replaced every time LinkMeter is upgraded and you will lose all changes. Instead, create new files for your scripts. The system first looks for alarm-all, and executes that. If the return value of that script is zero (the default), the system looks for a file named alarm-{probeidx}{alarmtype}. To not execute the alarm-specific script, exit alarm-all with a non-zero return code (e.g. exit 1).

For example if the Pit probe high alarm is going off, it will look for alarm-0H. These files can be a shell scripts, lua scripts, or a regular ARM ELF binaries. These recipes can be used for either an alarm-specific or alarm-all file. The files must be executable, i.e. chmod +x or they will not be run.

There are many variables available to use in your scripts. From a command prompt execute lmclient LMCF for a list. In addition, the alarm system adds al_probe, al_type, al_thresh, pn (alarm probe name), pcurr (alarm probe current value) variables. The al_set function can be used to change the value of the current alarm.

Recipes

All scripts

#!/bin/sh
# The first line of any shell script must begin with the above #! line 
# Comments begin with #

Turn the alarm off

#!/bin/sh
# Silence this alarm, it will ring again if re-armed
al_set 0

or

#!/bin/sh
# Disable this alarm, it will not ring again
al_set -$al_thresh

HeaterMeter Control - Shutdown

Often you want to turn off the Pit when your food is done, this can be done automatically from the Alarms configuration page. However, this is also easily done using lmclient to send a command to HeaterMeter to change the setpoint.

#!/bin/sh
# Lower the setpoint to 100
lmclient LMST,sp,100

HeaterMeter Control - Ramp Down

You can do more complicated setpoint control with a ramp down script.

#!/bin/sh
case $al_thresh in
  180) NEWSP=215; NEWAL=190; ;;
  190) NEWSP=205; NEWAL=200; ;;
  200) NEWSP=100; NEWAL=0; ;;
esac

lmclient LMST,sp,$NEWSP
al_set $NEWAL

HeaterMeter Control - Super Ramp Down

10 degrees too much? That's ok you can ramp down two degrees for every two degrees the meat climbs if you like

#!/bin/sh
if [ "$al_thresh" -gt 199 ] ; then
  # done
  lmclient LMST,sp,100
  exit
fi

NEWSP=$((sp-2))
NEWAL=$((al_thresh+2))
lmclient LMST,sp,$NEWSP
al_set $NEWAL

Time Delays (UNTESTED)

Often you may not want be notified when the alarm happens but some time after it happens. Cron can be used. Note cron only has per-minute resolution so don't try to make things happen every N seconds. This example calls the alarm-all script 1 hour after the alarm triggers.

#!/bin/sh
# If no parameter, this is a regular alarm
if [ -z "$1" ] ; then
  NOW=`date +%s`
  # Set target for 1 hour from now 3600=seconds
  WHEN=$((NOW+3600))

  TARGET=`date -D "%s" -d $WHEN +"%M %H %d %m"`
  echo "$TARGET * /usr/share/linkmeter/alarm-all RING${al_probe}" | crontab -

  # make sure cron is started, it won't start if there is no crontab at boot
  [ -z "$(pidof crond)" ] && /etc/init.d/cron start
else
  # This is the cron callback
  # Don't fire again
  crontab -r

  # Do whatever you want here, using another recipe
fi

Alarm Script Variables

Common Variables

Variable	Description
al_prep	Preposition describing alarm (above/below)
al_probe	Index of ringing alarm (0-3)
al_set	FUNCTION change current alarm threshold
al_thresh	Threshold of ringing alarm
al_type	Type (L/H) of ringing alarm
sp	Setpoint
pcurr	Current temperature of ringing alarm
pcurr0, pcurr1, pcurr2, pcurr3	Current temperatures
pn0, pn1, pn2, pn3	Probe names

Configuration Variables

Variable	Description
fmin, fmax	Blower min/max
ip	IP adddress of LinkMeter
lb	LCD Backlight
lbn	Home Mode
ld	Lid detect duration
le0, le1, le2, le3	LED trigger/invert
lo	Lid detect offset %
oflag	PID output flags
palh0, palh1, palh2, palh3	Alarm high thresholds
pall0, pall1, pall2, pall3	Alarm low thresholds
pca0, pca1, pca2, pca3	Steinheart A coefficients
pcb0, pcb1, pcb2, pcb3	Steinheart B coefficients
pcc0, pcc1, pcc2, pcc3	Steinheart C coefficients
pcr0, pcr1, pcr2, pcr3	Steinheart resistances or thermocouple scale
pidb, pidp, pidi, pidd	PID constants
po0, po1, po2, po3	Probe temperature offset (config)
prfn0, prfn1, prfn2, prfn3	Probe RF mapping
pt0, pt1, pt2, pt3	Probe type
smin, smax	Servo min/max position (10us)
ucid	HeaterMeter version

MSMTP Configuration

The mail transfer agent "msmtp" must be configured before any of the sendmail (email/SMS) commands will work. The web interface for this is under Services -> SMTP. If you prefer editing files, edit /etc/msmtprc with the information appropriate for your mail server

SMTP over SSL / Gmail

account default
host smtp.gmail.com
port 465
auth on
tls on
tls_certcheck off
tls_starttls off
from [email protected]
user [email protected]
password password

Hotmail / Windows Live Mail

account default
host smtp.live.com
port 587
tls on
tls_certcheck off
auth on
from [email protected]
user [email protected]
password password