29 Palms Demonstration

1
29 Palms Demonstration

• The TinyOS code behind the demo

2
Major application blocks

• Data collection
• Data analysis
• Data sharing
• Time Synchronization
• Velocity calculation
• Task Flow/Use
• Data recording/querying

3
Data collection

• Periodic events trigger sampling of ADC data
• Events generated using the CLOCK.comp component.
• TOS_CALL_COMMAND(TRAFFIC_CLOCK_INIT)(128, 2)
• void TOS_EVENT(TRAFFIC_CLOCK_EVENT)()
• Collection is initiated by using ADC.comp
• TOS_CALL_COMMAND(TRAFFIC_GET_DATA)(MAG_CHANNEL1)
• char TOS_EVENT(TRAFFIC_CHANNEL1_DATA_EVENT) (int
  data)

4
Data Analysis

• Raw sensor readings are filtered using IIR
  filters to detect anomalies (like a car passing)
• ch-gtfirst ch-gtfirst - (ch-gtfirst gtgt 3)
• ch-gtfirst ch-gtreading
• Or
• first (first 7 / 8) reading
• Or
• Rn 7Rn-1 READINGn where first/8

5
Data sharing

• Each device sends data to all surrounding nodes
• TOS_CALL_COMMAND(TRAFFIC_SUB_SEND_MSG)(TOS_BCAST_A
  DDR,
  AM_MSG(mags_msg), VAR(buffer)
• Each node keeps a buffer of data points that have
  been collected for this observation
• Each node check to make sure that an observation
  received isnt duplicated
• for (i0 i lt n i)
• if (VAR(node)(int)i nid)
• return
• All new readings are forwarded out again
• CRC check used on all transmissions

6
Time Synchronization

• Each node broadcasts out its version of the
  current time every 8 seconds
• Any node that falls behind updated its clock to
  the current time
• Nodes synchronized to /- 1/32 s
• Time stored in 32 bits of precision allowing for
  use of wall clock based timing

7
Velocity Calculation

• Velocity calculated using least squared on data
  points collected
• Least squares requires inversion of 2x2 matrix
• Using 16 bit math requires careful choice of
  input data
• Raw readings are shifted and scaled to prevent
  overflow/underflow
• Lowest time reading set to 0 and lowest position
  estimation set to 0

8
Must Calculate..

• Matrix to invert Requires n, ?x2, ?x
• Matrix inversion requires determinant
  calculation, several multiplies and divides
• Position estimation of each node.
• Resulting calculation does not determine the
  actual speed, instead results in two numbers when
  divided result in the speed
• Prevents underflow over larger range of vehicle
  speeds

9
Data Recording

• Vehicle detection events are stored into the
  EPROM log
• CarEvent foo (CarEvent)VAR(read_msg)1.data
• foo-gtspeed VAR(speed)
• foo-gttime VAR(car_time)
• foo-gtdet VAR(det)
• foo-gtid TOS_LOCAL_ADDRESS
• TOS_CALL_COMMAND(TRAFFIC_SUB_SEND_MSG)(0xff,19,VA
  R(read_msg)1)
• TOS_CALL_COMMAND(TRAFFIC_APPEND_LOG)(VAR(read_msg)
  1.data)
• VAR(max_log)

10
Data Retrieval

• Data is simultaneously pulled out of the EEPROM
  and onto the radio.

char TOS_EVENT(TRAFFIC_SUB_MSG_SEND_DONE)(TOS_MsgP
tr msg) if(msg (VAR(read_msg)(int)VA
R(read_msg_ptr)))
VAR(entry) if(VAR(entry) lt
VAR(max_log))
TOS_CALL_COMMAND(TRAFFIC_READ_LOG)(VAR(entry),
VAR(read_msg)(int)VAR(read_msg_ptr).data)
VAR(read_msg_ptr) 1
TOS_CALL_COMMAND(TRAFFIC_SUB_SEND_MSG)(TOS_BC
AST_ADDR, AM_MSG(TRAFFIC_READ_MSG), (VAR(re
ad_msg)(int)VAR(read_msg_ptr)))