Plan for Mini Car Computer
Ideas for use
- mpd server- xbmc (local movie play for trips)
- probably less trouble to just use a tablet, assuming infrequent use
- continual webcam snapshots to storage (EXIF tagged with GPS)
- live video storage (2 streams preferable)
- 2 streams for??? One high rate and one low rate???
- push button high res camera snapshot to storage
- GPS logs
- upload automatically via Wifi when in range of known AP
- some uploads continually via 3G (vodem or wifi repeat i.e. portable vodafone AP)
- G meter/logger (accelerometer)
- eg. 3-axis accelerometer NZD$39
- eg. 9DOF IMU NZD$179
Misc Notes
- Encrypted storage for logs somehow- GPG public key encryption
- public key is use to encrypt files
- private key (which is not on the device) is used to decrypt
- IR rx for user interface via a remote
- accelerometer
- car info? (misc car logging? temperature?)
- LCD display?
- engine status (to allow orderly shutdown when engine stopped)
- USB ports required somewhere:
- GPS
- music flashdrive (or HDD)
- keypad?
a10Core notes
- boot scripts:- standard TinyCore scripts:
- /opt/bootsync.sh is executed first, before console prompt appears
- this is the place to put anything that tweaks the user home
- /opt/bootlocal.sh is executed after console prompt appears
- this iterates over /opt/bootlocal.d
- KMW additions - /opt/bootlocal.d:
- scripts are executed in lexical order
- they need to be executable, as per normal...
- filenames are constrained to alphanum/underscore/dash
- filenames containing dots are ignored!
- usual way to disable a script is to rename it something.DISABLED
- syslog: /var/log/messages
- my logs: /var/log/usr
- boot log: /var/log/usr/boot*.log
Wifi Notes
- normal wifi kernel module used by mini-x is 8192cu- HostAP would be useful for phone to connect to, but ad-hoc wifi would be sufficient (needs rooted phone)
- potentially useful HostAP links
- http://home.comcast.net/~tomhorsley/hardware/rtl8192cu/rtl8192cu.html
Power Management Notes
- power management- Managed startup/shutdown with vehicle use
- Possibility of keeping it running when not in vehicle
- uploads via home wifi
- security functions e.g. geofencing, remote webcam monitoring for stalking
- simplest option is perhaps to have it powered by a 7Ahr battery which is continuously charged when car is running
- careful not to suck power from car battery when engine is not running
- computer needs awareness of current power source so it can initiate orderly shutdown when engine is turned off
- may need some handling for instances where power is lost briefly or car restarts just after mini-x shuts down
- just before mini-x starts shutdown sequence, assert a signal to power management which indicates that power should be restored *after* it is cut, if car power resumes
- minimum requirement:
- I/O:
- car power status signal to mini-x so it knows that power is about to die
- functionality:
- sustain power for 10s (or some other time) after car is turned off
- enough time to close logs cleanly and shutdown mini-x
- mini-x has no control and therefore has no risk of draining car battery
- better approach (could be achieved with a couple of relays and no real smarts):
- I/O:
- signal to mini-x so it knows that power is about to die
- signal from mini-x to shutdown power
- functionality:
- sustain power to mini-x until signal from mini-x says to shut down
- risk of draining car battery if mini-x loses its marbles
- even better approach:
- I/O:
- signal to mini-x so it knows that power is about to die
- signal from mini-x to shutdown power
- functionality:
- sustain power to mini-x until signal from mini-x says to shut down
- limit max duration of power sustaining (eg. to 15min)
- time limit ensures that mini-x can never exhaust car battery
More Power Management Notes
- connection to host- minimum requirements:
- 1 signal to rPi to indicate current main power status (car running or off)
- 1 signal from rPi to request shutdown
- digital I/O is simple to connect to rPi
- USB would allow more flexibility to use this board for other things
- main power status input
- pref via R network with some voltage limiting so that it could be used for 12V or 5V or something else
- pref with schmitt input or such so that it has sharply defined threshold and does not get upset by slowly dropping voltage
- optional bridge rectifier for sensing AC?
- optocoupled input for sensing AC mains?
- optional analog sensing so as to measure input voltage?
- space for small C for transient suppression (or could do this in software)
further options:
- measure car 12V voltage as well as own battery voltage?
- extra signal to rPi to indicate impending SLA battery failure and shutdown
- domestic usage
- control a mains relay (or SSR/triac) so that we can use it for a domestic device
- pref optocoupled for safety
- could have 2 controlled outputs so that it can manage its own mains as well as another device?
- mains power loss sensing?
- optional timer in PSU controller to restore power after "x" time period
- eg. to use for a device which powers on and runs a scheduled backup of something every day
Last edited by KarlMW:
add some more power management ideas to consider
Fri, 27 Dec 2013 18:22 UTC [diff]
add some more power management ideas to consider
Fri, 27 Dec 2013 18:22 UTC [diff]
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CategoryRaspberryPi
CategoryVehicles
CategoryXBMC
CategoryIdeas
CategoryKMWDiscussions