Odd behavior from my Propeller

DRMorrison · 2014-07-12 13:13

I'm noticing some odd behavior from my Propeller, and am wondering if anyone else has seen this sort of thing, or can
tell me what I'm doing wrong here.

In the Main method below, upon startup, the first number printed for "i" is 22, unless I initiate it with i := 0
as shown below commented out. If I set i to zero at the top, then i gets printed as 0, as expected.

I understood that all local variables get set to 0 upon startup. Am I missing something here?
I've included the entire code, just in case my problem is someplace else and I'm not seeing it.

This is what it looks like on the LCD the first time thru:

-168938 delta
0 restarts
22 trials
0 pin 2

And then when I set i to zero, it looks like this:

-161433 delta
0 restarts
0 trials
0 pin 2

In both cases i increases by one each time thru the repeat loop, and is updated to the LCD screen.
And I've reloaded this numerous times. I've even tried loading this into EEPROM.

Daniel

CON      
                         
 _clkmode  = xtal1 
 _xinfreq  = 5_000_000

 RC_Pin = 0   'circuit input pin
 LCD_TX = 1       'LCD comm pin                        
 
VAR
 LONG Value, starts, r1, r2
 
OBJ
  LCD  : "FullDuplexSerial.spin"

PUB Initiate 

 LCD.start(LCD_TX, LCD_TX, 00, 19_200)
 waitcnt(clkfreq/100 + cnt)
 LCD.tx(12)                     'clear screen, Form Feed
 waitcnt(clkfreq/100 + cnt)     ' must wait 5ms after a Form Feed
 LCD.tx(22)  
  
 dira[1]~~                      'LCD tx on pin 1
 dira[16]~~
 Main
 
PUB Main | i, pinstate
 'i := 0                    [COLOR=#ff0000] 'IF I DON'T USE THIS, i PRINTS AS 22 INITIALLY[/COLOR]
 repeat
  Check_Phone
  LCD.tx(128)                      'line 0, pos 0  
  LCD.dec(r2 - r1)                    'print diff.
  LCD.str(string(" delta   "))
  LCD.tx(148)                      'line 1, pos 0
  LCD.dec(starts)               'print average
  LCD.str(string(" restarts "))
  LCD.tx(168)                      'line 1, pos 0
  LCD.dec(i)              [COLOR=#ff0000] 'THIS IS PRINTING AS 22, UNLESS SET TO 0 FIRST[/COLOR]
  LCD.str(string(" trials "))
  LCD.tx(188)
  pinstate := ina[2]
  LCD.dec(pinstate)
  LCD.str(string(" pin 2 "))
  i += 1
 
PUB Check_Phone | delta    'Phone watchdog; check to see it phone is ON  FN

 Measure
 r1 := Value   
  
 outa[16]~~                     'Force leds to light  
 waitcnt(cnt + clkfreq/2) 
 Measure              
 r2 := Value 

 outa[16]~ 
 ctra := 000 << 26
 
 delta := r2 - r1
 if delta  <= 0               'if lights are on, return, else start phone
  return  
       
 Start_Phone
   
PRI Measure                  'Use RC circuit to check phone's status
 ctra := 000 << 26 | RC_Pin  ' Setup
 frqa := 1
 outa[RC_Pin]~~                 ' Set pin to 3.3V
                     
   dira[RC_Pin]~~                   ' Set pin as output
   waitcnt(cnt + clkfreq / 1000)    ' charge the capacitor for 500u
   phsa := 0                        ' clear counter
   dira[RC_Pin]~                    ' set pin as input
   waitpne(|<  RC_Pin,|< RC_Pin, 0) ' wait for to V get to 1.6V
   Value := phsa                 ' store the count in the array
   waitcnt(cnt + clkfreq / 10)

PUB Start_Phone                 'Cycle phone's power button   FN

 starts += 1

Phil Pilgrim (PhiPi) · 2014-07-12 13:15

DRMorrison wrote:

I understood that all local variables get set to 0 upon startup.

They do not. Only return values and VAR variables are intialized to zero. Local variables can start with any value, depending on what was on the stack before the method call.

-Phil

DRMorrison · 2014-07-12 14:10

Well of course, I knew it had to be something simple as operator error. i.e. my brain!

Thanks, Daniel

Odd behavior from my Propeller

Comments