Heya Guys
I tried the example from the help file on PWM, and I get the an erro saying TrisB is not defined.  Any Ideas?

[Quoting: "Somebody"]
' -------------------------------------------------------------------------
' Program Description
' -------------------------------------------------------------------------
'
' Uses PWM through an RC network to create an analog voltage.

' -------------------------------------------------------------------------
' Device Settings
' -------------------------------------------------------------------------
DEVICE          SX28, OSC4MHZ, TURBO, STACKX, OPTIONX
FREQ            4_000_000
ID              "PWM"
' -------------------------------------------------------------------------
' IO Pins
' -------------------------------------------------------------------------
DAC             VAR     RB.0                    ' output to RC network
' -------------------------------------------------------------------------
' Variables
' -------------------------------------------------------------------------
angle           VAR     Byte
duty            VAR     Byte tmpB1           VAR     Byte
tmpB2           VAR     Byte
' =========================================================================
 PROGRAM Start
' =========================================================================
' -------------------------------------------------------------------------
' Subroutine Declarations
' -------------------------------------------------------------------------
SIN             SUB     1                       ' returns sine of angle
COS             SUB     1                       ' returns cosine of angle
' -------------------------------------------------------------------------
' Program Code
' -------------------------------------------------------------------------
Start:
 DO
   FOR angle = 0 TO 255                        ' sweep through angles
     duty = SIN angle                          ' get sine of angel
     duty = duty + 127                         ' bias to 2.5 v
     PWM DAC, duty, 1                          ' charge RC network
   NEXT
 LOOP
' -------------------------------------------------------------------------
' Subroutine Code
' -------------------------------------------------------------------------
' Use: value = SIN angle
' -- "value" returned as signed byte (-127 to 127)
' -- angle is expressed in Brads (0 - 255)
SIN:
 tmpB1 = __PARAM1                              ' get angle
 tmpB2 = tmpB1                                 ' make copy
 IF tmpB2.6 = 1 THEN                           ' in 2nd or 4th quadrant?
   tmpB1 = 0 - tmpB1                           '   yes, move to 1st/3rd
 ENDIF
 tmpB1.7 = 0                                   ' reduce to 1st quadrant
 READ SineTable + tmpB1, tmpB1                 ' read sine
 IF tmpB2.7 = 1 THEN                           ' was angle in 3rd/4th?
   tmpB1 = 0 - tmpB1                           '   yes, adjust
 ENDIF
 RETURN tmpB1
' -------------------------------------------------------------------------
' Use: value = COS angle
' -- "value" returned as signed byte (-127 to 127)
' -- angle is expressed in Brads (0 - 255)
COS:
 tmpB1 = __PARAM1 + $40                        ' get angle (adjust phase)
 tmpB1 = SIN tmpB1                             ' call sine table
 RETURN tmpB1

' =========================================================================
' User Data
' =========================================================================
SineTable:
 DATA  000, 003, 006, 009, 012, 016, 019, 022
 DATA  025, 028, 031, 034, 037, 040, 043, 046
 DATA  049, 051, 054, 057, 060, 063, 065, 068
 DATA  071, 073, 076, 078, 081, 083, 085, 088
 DATA  090, 092, 094, 096, 098, 100, 102, 104
 DATA  106, 107, 109, 111, 112, 113, 115, 116
 DATA  117, 118, 120, 121, 122, 122, 123, 124
 DATA  125, 125, 126, 126, 126, 127, 127, 127
 DATA  127

It's TRIS_B
Bean.

Sorry I typed it from memory (not good)
it still does not mentions tris_b in the example from the manual however
Anyone advise?

I copied what you posted and it compiled without errors for me.  What version of SX/B are you using?  You can find the latest version in a "sticky post" at the top of this forum.

heya
Newest version, downloaded 2 days ago :(
Got it working now, was a bug with the ide, copied the code, restarted pasted and it worked.

Now I cannot get it to simply dim an led now :(
regardless of duty being 10 or 250, led is same brightness, is any extra circuitry required?  as with the picaxe, you just use an led, and a resistor.

Is the LED connected to RB.0?

You have: PWM DAC, duty, 1>
RB.0 will PWM for 1ms.  That's not long enough to see anything.  Are you figuring it's going to stay at the charged voltage so that you can base your brightness on it?  That won't work like that.

Ah sorry i stole that code from the pwm example.

I did try just pwm with a duty between 1 and 255 and the duration as 1000 the led comes on but thats it no variance in brightness, always the same brightness regardless of duty.

DJH,
 You need to create the simplest program that demonstrates the problem.

 If you just want PWM then there is no reason that "PWM pin, value, duration" won't work. value and duration must be from 0 to 255.  This is all right in the help file. Duration cannot be 1000.

Bean.

ok this has the same problem led just stays on (obviously this is not all the code, the rest is just declarations)
Start:
 DO
   FOR duty = 0 TO 255                        ' sweep through angles
     PWM DAC, duty, 250                          ' charge RC network
   NEXT
 LOOP

Nobody has said if i can even do this with just an led and a resistor?

OK -- Yes, all you need is a resistor and an LED.
This program works (the LED starts OFF and then gradually increases to full ON), I am watching it right before me --

DEVICE sx28, oschs3, TURBO, OPTIONX
IRC_CAL  IRC_SLOW
FREQ     75_000_000 

PROGRAM  Start 
  
duty  var  byte 
  
TRIS_A = $00 
  
Start:
DO
FOR duty = 0 TO 255 ' sweep through angles
PWM RA.0, duty, 50 >speed of change
NEXT
LOOP 
I am using RA.0 for the output, and I am not using a capacitor or RC network at all (and I don't know why you are.)  
You will have to change the FREQ directive to match your time-base.

Okay I forgot to mention. Make the program as simple as possible. But then post the ENTIRE program. There are many things you could have wrong in the parts you haven't posted.

You got to help us help you...

Bean.

Thanks guys been a hard day, Im not using a cap or RC network, those comments were left over from the code taken from the manual.

I am now trying this code but I just get a "Tris_a not defined" error.

[Quoting: "Somebody"]
DEVICE sx48, OSC4MHZ
IRC_CAL  IRC_SLOW
FREQ     4_000_000
PROGRAM  Start duty  var  byte
TRIS_A = $00
Start:
DO
FOR duty = 0 TO 255 ' sweep through angles
PWM RA.0, duty, 50 ' charge RC network
NEXT
LOOP

hmm when it tries to compile it opens a *.src file and says that tris_a is not defined and it highlights a line in the assembly, if i just delete that line it works :S

[Quoting: "Somebody"]
MOV FSR,#__TRISA  

Any ideas why this would happen?  Sorry Ive been getting used to the propeller, but need to use the SX for it's larger number of outputs and cheaper price.

Okay, now we are getting somewhere ! The missing piece of the puzzle is that you are using the SX48.

This can be corrected by adding a line: __TRISA  CON  __TRIS
I will make sure this is corrected in the next release of the compiler.

Thanks,
Bean.

woohoo my inadequencies as a programmer came in helpful?  :smile:

hmm if I try to program the below code with or without the TrisA = nothing happens, no error box pops up as usual or anything, just "SX/B Error" in the bottom of the application.

[Quoting: "Somebody"]
DEVICE sx48, OSC4MHZ
IRC_CAL  IRC_SLOW
FREQ     4_000_000
PROGRAM  Start duty  var  byte
cntr var byte
__TRISA  CON __TRIS
'TRIS_A = $00
Start:
duty = 255
DO
FOR cntr = 0 TO 255 ' sweep through angles
duty = duty - 1
PWM RA, duty, 50 ' charge RC network
NEXT
low ra.0
pause 10000
LOOP

You have not specifed a pin for PWM. You have RA which is a whole port.

Bean.

i've been using the r/c network in the example, w/ both a 1uf cap & .1 ufd cap (& changing the charge time from 10 to 1..). both configurations w/ a 10K resistor.. What I've addad is a 2n7000 series J-mosfet on the output & the hold time is outragous !!! I can send a single PWM  instruction & the circuit will hold the val for many MINUTES.. not secs or millsec's..

in trying to cut down code space, however, I've hit a snag... I need to be able to specify the PIN in the PWM command as a variable... I'm sending pulses out each RA & RB port bit ( 16 seperate PWM commands..yuk) & want to use a generic 'send' subroutine, passing pin & duration as params... any ideas??

thanks,
jesse in venice..

Just a quick note to say how impressed I am with Bean for his work on the SX/B compiler and with Parallax for sponsoring it. People who program in BASIC rather than ASM or C really owe you guys a debt of gratitude. Same day help with programming, bug report and fix, and quick turns on compiler versions are sadly lacking in this industry.