(include notes from hw meeting on 20020806 + brief summary of design descisions/options/etc+ –nik gaffney)

Work is continuing on a new wireless sensor aquisition system, to hopefully overcome the problems found with all the previous systems. The current version is still built on a series of comprimises between price,availability,elegance,wirelessness and flexibility, however it should be edging towards something better.

Hardware setup

  • CerfBoard (strongARM) see: Cerf Notes
  • 3d acceleromter units
  • WCF12 802.11b compact flash card
  • sony info lithium battery + 5V regulator

Software setup

  • calibration + sensing code (gpio → OSC )

details can be found in the techspec (linked from Project Txoom System ), code is in cvs, and notes can be found in the Cerf Notes node.


  • sampling periodicity: ~10ms/vector or as close to 4ms/point as possible (100-250Hz)
  • latency: should be as low as possible. if a vector takes too long to store, send points.
  • thruput: accelerometer data is single byte (8bit) per point.

calulations for 2x3d acceleromters (for reference)

  • 8bits x 6axis = 48bits/0.004s = 12kbps (at 4ms sampling rate) per player.
  • 8bits x 6axis = 48bits/0.01s = 4800bps (at 10ms sampling rate) per player.
  • 8bits x 6axis = 48bits/0.02s = 2400bps (at 20ms sampling rate) per player.

(note: raw data, no correction, or stop bits)

players 4ms 10ms 20ms
1 12k 4800 2400
2 24k 9600 4800
3 36k 14.4k 7200
4 48k 19.2k 9600
5 60k 24k 12k

see also CerfNotes for more details

wired connection

  • prerequisites
    • ceed
    • sensors + cables
    • network with DHCP server
    • power suppply or batteries
  • attach ethernet cable to the ceed box
  • powerup ceed
  • wait for a while,
  • find its ip
    • run nmap or similar to find which ip# it has …
    • eg. # nmap -sP
    • check which ips are in use before + after turning the ceed on
  • check there is something listening to port 5333 on the host machine (eg, 'oz', 'nc -lup 5333' or an OSC capable program)
  • connect to the ceed # ssh -lroot 10.0.0.x
  • load the adxl module # insmod adxl.o
  • run the sensor program in test mode # ./operate -c debug.conf -h <host.ip>
  • check which chanels are active
  • edit the operate.conf file if required.
  • run the sensor program # ./operate -h <host.ip>
  • sit back + relax

wireless connection

  • make sure the base station is active
  • check SSID set to f0am (using ap-config under GNU/Linux)
  • contine as above from the 'powerup ceed' step

see also IPaq Notes for more details

these notes are meant as a quick guide to setting up the ipaq + sensor sets for the tgarden/tx0om system(s). insprired by my lack of memory, and the fact that teh wearables can be fickle creatures, .. .


  • connect access point to network
  • turn on ipaq
  • press the “Q” button to boot linux
  • open 'Utilities → Input Methods → Xkbd' by clicking on the screen
  • open 'Root' window by clicking on the screen
  • (optional) type 'bash' for smoother shell interaction
  • type 'ifconfig' and see if there is an entry for 'wlan0'
  • type 'pump' and check ifconfig again.
  • if there is no entry for 'wlan0' device, type…
ifconfig wlan0 netmask up 
(substituting the suitable ip# and mask for the network)
  • check ifconfig again. try to ping a host (using ip#)
  • if there is no route to host, try typing…
route add default gw 
(or whatever the ip# of the access point is)
  • type 'route' and check the routing table is correct
  • dont bother with /etc/resolv.conf unless you must
  • it should now be possible to connect to the ipaq using ssh

now, the sensors…

  • make sure the stamp is charged + sensors connected
  • on the ipaq, enter 'cat /dev/ttySA0' to display data comming in the serial port
  • connect the stamp to the ipaq serial port
  • sit back + watch the numbers,. ..
  • if there are no numbers, there is a problem (find it + continue)


  • cd to 'sensors' directory of $HOME
  • calibrate -c &<sensor number>
  • check the min + max values for each sensor channel


  • operate -h <host running oz>
  • sit back + relax

see also: Mobile Computing, Wearable Computing, Sensor Technology, Human Interface System

  • project_txoom_wearables.txt
  • Last modified: 2022-10-05 11:58
  • by nik