Nuts and Volts - January 2009

Stage Separation

Previously, digital input IN 6 of the sensor port was connected to a switch that triggered a recording run when the rocket left the launch rail. An alternative method of

triggering is now used that frees this input for other tasks (e.g., detecting booster-stage separation). The trigger subroutine now monitors vertical acceleration and initiates recording when a pre-defined threshold is exceeded twice within a specified period of time. Although it is no longer possible

setfreq m8

'Set internal clock to 8MHz

symbol memmin = 0
symbol memmax = 32766
symbol memaddress = W6
symbol liftoff = 160
symbol redled = 2
symbol download = 3
symbol booster = pin6
symbol cable = pin7
symbol power = 0

'Start address
'End address
'Memory counter (word)
'Set trigger level at 2G
'Define constants.....

high power
pause 4000

'Hold power on
'Wait for power to settle

playback:
pause 2000
serout download, T4800, (CR,CR,CR,"CLEARDATA",CR)
pause 2000
serout download, T4800,
("LABEL,",",",",","Acc,Apo,Sun,Evt",CR)
pause 2000
serout download, T4800,

'Always download data on power-up

'Setup SelmaDAQ export to MS Excel

("2 Stage Rocket Instrumentation V.6",CR)

i2cslave %10100000, i2cfast, i2cword

'Configure master 12c port

for memaddress = memmin to memmax step 6 'Generate memory address in steps of 6
 readi2c memaddress, (b0,b1,b2,b3,b4,b5) 'Read data from six FRAM addresses
  serout download, T4800,("DATA,",",",",",#w0,",",#w1,",",#b4,",",#b5,CR) 'Send data in SelmaDAQ compatible format
 next memaddress 'Next three addresses

if cable = 0 then  trigger
low power

'Start trigger routine if cable disconnected,
'else, power down

trigger:
readadc 0,b0
  low redled
 pause 100
 high redled
 readadc 0,b1
  pause 100
if b0> liftoff AND b1> liftoff then record

goto trigger

record:
i2cslave %10100000, i2cfast, i2cword

for memaddress = memmin to memmax step 6
 b5 = pins AND %11000000
  readadc10 0, w0
  readadc10 2, w1
 readadc 1,b4
 writei2c memaddress, (b0,b1,b2,b3,b4,b5)
  pause rate
 next memaddress
power low

'Acceleration monitoring loop
'Measure acceleration
'Red LED on

'Red LED off
'Monitor acceleration again after delay

'If acceleration exceeds trigger level twice within loop
'time, start recording

'Configure master 12c port

'Generate memory addresses in steps of 6
'Read input bit 6 & input bit 7
'10-bit acceleration reading
'10-bit pressure  reading
'8-bit light level reading
'Write six bytes of data to FRAM
'Set scan rate
'Next three addresses
'Powerdown