Newbie, help needed

Scooter · 2010-12-19 15:09

Hello, after several (simple, but working fine) projects using the BS2 module, for my new project i need a Propeller.
I'm at the very first step about learning how to program in Spin (i'm only able to do basic I/O functions), so please
be patient..
My project is to control an R/C tank using a custom electronic, basically what i would like to obtain at the moment
is to read four channels from a receiver (typical 1 to 2 mS) and do different actions according to the signal decoded.
I rolled around Post and OBEX and i found the RX & RX_demo OBJ that i modified to read only one channel, but now
i'm stuck about reading and compare the [pulseOut] stored in phsa register...
I'm sure i made some mistake or missed something but where ?
Thanks to all for the help and sorry for the bad english...
Ivan

Here's the modified code :

VAR
long Stack[20] 'Stack space for new cog
PUB Measure (pulseOut)
{{Continuously acquire pulse width on the pin at address pinIn,
and store as microseconds at the address pulsesOut }}
ctra[30..26] := %11010 ' Set mode to "logic A"
ctra[5..0] :=0 ' Set input pin 0
frqa := 1 ' Increment phsa by 1 for each clock tick
repeat
waitpeq(|< LONG[0], |< LONG[0], 0) ' Wait for pulse to start
waitpne(|< LONG[0], |< LONG[0], 0) ' Wait for pulse to stop
LONG[pulseOut]:= phsa /(clkfreq/1_000_000) ' Calculate Width, in microseconds
phsa := 0 ' Reset the counter

Kevin Brown · 2010-12-19 15:50

Check out the contest area and look at the AttoPilot project it has code for reading the R/C receiver
http://www.parallax.com/tabid/726/Default.aspx

ElectricAye · 2010-12-19 17:35

Ivan,

When you post code, place your code between code tags, like what you see below but be sure to remove all of the spaces I placed between the brackets.

[ code ]

[ / code ]

Without the code tags, the indentation is lost and it's hard to read your code.

Scooter · 2010-12-19 23:43

Hello ElectricAye, sorry for the mistake, message edited should be correct now...
Thanks
Hello Kevin Brown, i followed your link but no code at all...
Thanks

Ivan

StefanL38 · 2010-12-20 09:41

Hi Scooter,

CODE not QUOTE

code looks like this and keeps all the indention which is an essential element of the codestructure

as the indention is lost through QUOTING I guess you meant it that way:

for a precise clock you should always use these constants
like shown in the CON-section

the value of xinfreq must match the frequency of the chyrstal you are using
if you have a chrystal with more than 6.25 MHz PLL-mode 16x is not possible
f.e. with an 8 MHz chrystal you should use

_clkmode = xtal1 + pll8x

CON
  _clkmode       = xtal1 + pll16x
  _xinfreq       = 5_000_000


VAR
  long Stack[20] 'Stack space for new cog

  
PUB Measure (pulseOut)
  {{Continuously acquire pulse width on the pin at address pinIn,
  and store as microseconds at the address pulsesOut }}
  ctra[30..26] := %11010 ' Set mode to "logic A"
  ctra[5..0] :=0 ' Set input pin 0
  frqa := 1 ' Increment phsa by 1 for each clock tick
  
  repeat
    waitpeq(|< LONG[0], |< LONG[0], 0) ' Wait for pulse to start
    waitpne(|< LONG[0], |< LONG[0], 0) ' Wait for pulse to stop
    LONG[pulseOut]:= phsa / (clkfreq / 1_000_000) ' Calculate Width, in microseconds
    
    phsa := 0 ' Reset the counter

there are several objects in the obex for receiving servo-signals

best regards

Stefan

Scooter · 2010-12-20 13:38

Hi Stefan
Sorry i made a mess with the insert buttons.
Yes the code is just like that, i'm using a 5 MHz crystal and i put the CON statement in the code, i compiled and downloaded into Propeller with no errors, my problem is how to compare the value stored in variable [pulseout] with another value. What i would like to do is to use a COG for each of four RX channel monitored, using it to compare the value in mS of the stick position i.e.

1.5 mS (neutral) : do nothing
from 1.6 to 1.750 mS : move a servo (or simply turn on a led)
from 1.9 to 2.0 mS : move another servo (or turn on another led)

But i'm not sure that a simple "IF (pulseout) > 1_600_000 AND < 1_800_000 then do something" is correct and works, also i was asking me if a single COG for every channel is the right way, with this code the COG always measure and store and must be called out from repeat for compare the results and turn on leds... maybe i should use a COG polling the other four.

Another question is : the RX supply is around 5 VDC the signal that usually is feed to a servo has this amplitude, reading various posts someone says "use a level translator 5V - 3V" someone else says a 4K7 to 10 Kohms is enough, at the moment i have connected the RX channel to pin 0 through a 4K7 resistor.

Thanks for the help

Best Regards

Ivan

Kevin Brown · 2010-12-20 20:45

Sorry about that the code for this on is hard to find try this link

http://www.parallax.com/tabid/704/Default.aspx

Scooter · 2010-12-25 15:17

Hello and Merry Xmas to everyone.

It's holyday and i have some spare time for try to learn some more.
Reading the docs found into parallax homepage i used these two codes to read a RX ppm signal, but i really don't understand how to compare "tHprobe" variable to another fixed value as i wrote in a previous post, there is someone that can explain me how to do?

Thanks a lot

Ivan

CON
  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000
 
VAR
  long tHprobe, tLprobe, pulseCnt, ref
OBJ
  probe : "MonitorPWM"
PUB MethodInMyApp
  probe.start(0, @tHprobe, @tLprobe, @pulseCnt)

VAR
  long cog, stack[20]
  long apin, thaddr, tladdr, pcntaddr
PUB start(pin, thighaddr, tlowaddr, pulsecntaddr) : okay
  apin := pin
  thaddr := thighaddr
  tladdr := tlowaddr
  pcntaddr :=pulsecntaddr
  okay := cog := cognew(PwmMonitor, @stack) + 1
 
PUB stop
  if cog
     cogstop(cog~ - 1)
PRI PwmMonitor
  ctra[30..26] := %01000
  ctra[5..0] := apin  
  frqa := 1
  ctrb[30..26] := %01100
  ctrb[5..0] := apin
  frqb := 1
  phsa~
  phsb~
  dira[apin]~
 
  repeat
    waitpeq(|<apin, |<apin, 0)
    long[tladdr] := phsb / 1_000_000
 
    phsb~
    waitpeq(0, |<apin, 0)
    long[thaddr] := phsa / 1_000_000
    phsa~
    long[pcntaddr]++
     dira[13] :=1
     !outa[13]
     waitcnt (1_000_000 + cnt)

ElectricAye · 2010-12-25 15:31

Scooter wrote: »

...how to compare "tHprobe" variable to another fixed value...

If two variables are integers, then you can use binary operators like > or =>, etc. (see page 43 and 170, 171, etc of the Propeller Manual).

But if the variables are not integers, then you'll need to use one of the FloatMath32 objects for FCmp.

http://obex.parallax.com/objects/202/

or maybe:

http://obex.parallax.com/objects/689//

Of course, if you must compare two numbers like 1.75 and 1.15, you can multiply both by 100 and compare them as integers instead of using FCmp for decimals.

Is this what you're asking about?

Mike G · 2010-12-25 15:54

The code comments explain MonitorPWM.spin very well. I'm not exactly sure what you're asking.

simple compare

if (tHprobe > myvalue)
  'Do somehting

Scooter · 2010-12-26 07:33

Mike G wrote: »
The code comments explain MonitorPWM.spin very well. I'm not exactly sure what you're asking.

simple compare
if (tHprobe > myvalue)
  'Do somehting

Hello Mike G
Yes, this is what i would like to do and where i'm stuck...
i have a precise 1 mSec ppm signal connected at pin 0, i have (called at the end of the PwmMonitor OBJ code) a led blinking and i'm assuming that the code runs.
In the Main (as posted below) i have added the if/then condition to turn on a led when the signal applied is bigger than 1 mSec but it does'nt work.

Thanks

Ivan

CON
  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000
 
VAR
  long tHprobe, tLprobe, pulseCnt, ref
OBJ
  probe : "MonitorPWM"
 
PUB MethodInMyApp | data
 
  probe.start(0, @tHprobe, @tLprobe, @pulseCnt)
  data := (tHprobe / 1_000_000)
 
  if (data > 1_000_000)
     dira[9] :=1
     outa[9] :=1
     repeat

ElectricAye · 2010-12-26 08:04

Scooter wrote: »

... i have added the if/then condition to turn on a led when the signal applied is bigger than 1 mSec but it does'nt work.

When your program gets to the repeat statement, it will hang there forever and do nothing else. Is that what you want it to do?

Scooter · 2010-12-26 08:32

Hi ElectricAye
i'm trying to test the code and try to learn instead of simply cut & paste, lighting up a led is to see if it works. (my simple project is to read a ppm pulse widht from one channel R/C rx an move 2 or 3 servos in different position i.e. for 1.7 mS input -> servo 1 full forward, servo 2 full backward and so on.
i added the repeat only to have the led turned on and be able to see it. (maybe is wrong).
i'm assuming that the repeat should always compare "data" with 1_000_000 an lit the led if data is bigger (and maybe is wrong also).
I know that my questions are "dumb" but i am trying to learn by myself using the tutorials and the language differences will not help (my english is poor) but here in Italy seems that nobody use this amazing chip or the Basic Stamp.
Thanks
Ivan

Mike G · 2010-12-26 08:49

Use the Parallax Serial Terminal to view what's happening. In this case, your dividing by 1_000_000 when the tHprobe value is probably much smaller. Then you're checking if tHprobe/1_000_000 is greater than 1_000_000? It should not be right? Considering you just divided by 1_000_000 and 1_000_000 is a large number compared to the clock at 80MHz. It's kinda hard to figure out what you're expecting to happen. Adding comments help others follow along.

This debug script might be of some help.

CON
  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000
  CR            = 13
  CS            = 16  ''CS: Clear Screen      
  CE            = 11  ''CE: Clear to End of line     
  CB            = 12  ''CB: Clear lines Below 
  LF            = 10
 
VAR
  long tHprobe, tLprobe, pulseCnt, ref
OBJ
  probe : "MonitorPWM"
  pst   : "Parallax Serial Terminal.spin"
 
PUB MethodInMyApp | data

  PST.Start(115_200)
  probe.start(0, @tHprobe, @tLprobe, @pulseCnt)

  repeat
    pst.str(string("tHprobe: "))
    pst.dec(tHprobe)
    pst.char(CR)


    pst.str(string("tHprobe/1_000_000 = "))
    pst.dec(tHprobe / 1_000_000)
    pst.char(CR)

  {
  data := (tHprobe / 1_000_000)
 
  if (data > 1_000_000)
     dira[9] :=1
     outa[9] :=1
     repeat
     }

ElectricAye · 2010-12-26 08:51

Ivan,

Be sure to work your way through the tutorials one step at a time so you are not biting off more than you can chew at any one time.
If you want your program to keep comparing your variable data to 1000000 in a loop, then you must place a repeat command something like this:

Repeat 'Forever...
  If (data > 1000000)
     dira[9] :=1
     outa[9] :=1
    waitcnt (clkfreq*2 + cnt)

The waitcnt command will cause the program to wait at that point for 2 seconds so you can see your LED. See page 218 of the Propeller Manual for how the waitcnt command works.

Also, to get your LED to blink on only when data > 1000000, you'll need code to turn it off, too. Otherwise it will turn on and stay on forever.

As for your R/C problem, I'm afraid I don't know enough to help you with that. But I think you need to learn some more fundamentals about the code before rushing into complex functions.

Good luck!

Scooter · 2010-12-31 03:48

Hello
Follwing ElectricAye hints i managed to go step by step, here's the code that works for my purposes,
if someone would like to look in and tell me if there's something (and sure there is) that can be made different (better) or much more fast and "skinny" i will be glad.
Ivan

MainPWM

CON
_clkmode = xtal1 + pll16x
_xinfreq = 5_000_000
VAR
LONG Stack1[20]
LONG Stack2[20]
OBJ
'CH1 : "
'CH2 : "
CH3 : "pwm2"
CH4 : "pwm3"  
PUB MainPWM
CH3.Start
CH4.Start

PWM2

LONG Stack[10]
OBJ
Bup : "PWM_elev_up"
Bdw : "PWM_elev_down"
Rec : "PWM_recoil"
PUB Start
cognew (pwm2, @Stack)
PUB pwm2
repeat
  ref1 := (clkfreq / 500)  '2 mSec x recoil
  ref2 := (clkfreq / 800)  '1.2 mSec upper limit down
  ref3 := (clkfreq / 550)  '1.8 mSec upper limit up
  pin := 3
  ctra[30..26] := %01000
  ctra[5..0] := pin
  frqa := 1
  phsa~
  dira[pin]~ 
  waitpeq(|< pin, |< pin, 0)
  waitpeq(0, |< pin, 0)
  if phsa =>ref1
     Rec.Start
 phsa~
 long[pcntaddr]++
  ctra[30..26] := %01000
  ctra[5..0] := pin
  frqa := 1
  phsa~
  dira[pin]~ 
  waitpeq(|< pin, |< pin, 0)
  waitpeq(0, |< pin, 0)
  if phsa  =< ref2
     Bdw.Start
  phsa~
  long[pcntaddr]++
 ctra[30..26] := %01000
  ctra[5..0] := pin
  frqa := 1
  phsa~
  dira[pin]~ 
  waitpeq(|< pin, |< pin, 0)
  waitpeq(0, |< pin, 0)
  if phsa => ref3
     Bup.Start
 phsa~
 long[pcntaddr]++

PWM3

VAR
LONG thaddr, tladdr, pcntaddr
LONG pin, ref1, ref2
LONG Stack[10]
OBJ
Tleft  : "PWM_turnL"
Tright : "PWM_turnR"  
PUB Start
cognew (pwm3, @Stack)
PUB pwm3
repeat
 ref1 := (clkfreq / 550)  '2 mSec x turn R
 ref2 := (clkfreq / 800)  '1.2 mSec x turn L
 pin := 2
 ctra[30..26] := %01000
 ctra[5..0] := pin
 frqa := 1
 phsa~
 dira[pin]~   
 waitpeq(|< pin, |< pin, 0)
 waitpeq(0, |< pin, 0)
   if phsa => ref1
     Tleft.Start
   if phsa =< ref2
      Tright.Start
 phsa~
 long[pcntaddr]++

PWM_elev_up

PUB Start | tc, tha, t
ctrb[30..26] := %00100
ctrb[5..0] := 7
frqb := 1
dira[7]~~
tc := clkfreq /45   'cycle 20mS
tha := clkfreq /450 'pwm 2mS barrel up 
t := cnt
repeat 1
  phsb := -tha
  t += tc
  waitcnt(t)
dira[7]~
return

PWM_elev_down

PUB Start | tc, tha, t
ctrb[30..26] := %00100
ctrb[5..0] := 7
frqb := 1
dira[7]~~
tc := clkfreq /45   'cycle 20mS
tha := clkfreq /1_300 'pwm 0,7mS barrel down
t := cnt
repeat 1
  phsb := -tha
  t += tc
  waitcnt(t)
dira[7]~          
return

PWM_recoil

PUB Start | tc, tha, t, d
ctrb[30..26] := %00100
ctrb[5..0] := 8
frqb := 1
dira[8]~~
tc := clkfreq /45   'cycle 20mS
tha := clkfreq /450 'pwm 2mS barrel recoil 
t := cnt
repeat 10
  phsb := -tha
  t += tc
  waitcnt(t)
repeat d from 450 to 1_300 step 10
  tc := clkfreq /45   'cycle 20mS
  tha := clkfreq /d 'pwm 0,7mS barrel return
  t := cnt
  phsb := -tha
  t += tc
  waitcnt(t)
dira[8]~
return

PWM_turn_left

PUB Start | tc, tha, t
ctrb[30..26] := %00100
ctrb[5..0] := 6
frqb := 1
dira[6]~~
tc := clkfreq /45   'cycle 20mS
tha := clkfreq /1300 'pwm 0,7mS turn left 
t := cnt
repeat 10
  phsb := -tha
  t += tc
  waitcnt(t)
dira[6]~    
return

PWM_turn_right

PUB Start | tc, tha, t
ctrb[30..26] := %00100
ctrb[5..0] := 6
frqb := 1
dira[6]~~
tc := clkfreq /45   'cycle 20mS
tha := clkfreq /450 'pwm 2mS turn right 
t := cnt
repeat 10
  phsb := -tha
  t += tc
  waitcnt(t)
dira[6]~    
return

Newbie, help needed

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