Better understanding PULSIN

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- 5th May 2008, 11:06
Wirecut

Better understanding PULSIN

I would better understand how work PULSIN statement.

I'm using PULSIN of PICBASIC PRO rel 4.47 on a 16F877 at 20 Mhz for decode IR from remote, using Sony format.

In order to better understand, I would track the timing of PULSIN using one free output pin to view with a scope the beging/end of the PULSIN duration with the following statement:

for BitCount= 1 to 12
High SData: pauseus 1: low SData ' Before pulsin, generate a pulse wiewable with an oscilloscope.
pulsin IR_Sensor,0,IRpuls_len(BitCount)
High SData: pauseus 1: low SData ' Before pulsin, generate a pulse wiewable with an oscilloscope.

if IRpuls_len(BitCount) < 580 then
Packet.0[BitCount-1]=0
Else
Packet.0[BitCount-1]=1
endif
next BitCount

In my mind, I immagine that first there are an ON pulse as a witness of the PULSIN begin, then after 2,4 or 1,2 or 0,6 mS I should see the second ON pulse.

Running it, never I see the ON pulse in continuos phase, with begin/end of PULSIN, but in a random position. Take note that the "IRpuls_len(x)" contain the correct value of the pulse lenght, 2,4 mS, 1,2 mS and 0,6 mS.

Also working with DEFINE PULSIN_MAX with different value do not help to view the second pulse in timing with the end of PULSIN duration.

Any comment or consideration is welcome.

Ciao

Leo
- 5th May 2008, 12:06
mackrackit

The thing that might be giving you unexpected results is you are looking for the low state.

Code:

pulsin IR_Sensor,0,IRpuls_len(BitCount)

Change the "0" to "1" to read the high pulse.
- 5th May 2008, 13:38
Wirecut

Hi mackrackit,

the statement is correct, I read the "down" time of the signal, ad the value returned by PULSIN is correct and into the value that I aspect.

I do not see the pulse in phase with PULSIN generate by this statement

SData var PORTB.7 ' RB7 output pin for measurement pulse duration
.....
High SData: pauseus 1: low SDatapulse
.....

SData is aspected lengh one microsecond, and when is show have correct lenght, but non in phase with begin/end of PULSIN.

Ciao

Leo
- 5th May 2008, 19:55
mackrackit

I am not quite getting it.

You are talking about another VAR or CON (SDatapulse) that we do not know how it relates to everything else.

Can you post all of your code?
- 9th May 2008, 12:01
Wirecut

4 Attachment(s)

Sorry for delay to upload the code.

Also I have upload tree screenshot of a digital oscilloscope to better explain what happens.

Channel B show the incomin IR signal and channel A should show with the pulse of SData/PORTB.1 the begin/end of PULSIN.

You can see some missing SData/PORTB.1 pulse on the uploaded images, but belive me the IR code is correctly recognized of the incaming IR pulse duration and the array IRpuls_len(x) contain the correct pulse lenght.

The uploaded program 16F877_IR_pulsin.zip works correctly, but leave me unsatisfied about the use of PULSIN.

I will expect one pulse of SData/PORTB.1 at the begin of PULSIN and another pulse of SData/PORTB.1 at the end of the PULSIN statement, yust before the execution of the next statement, and no SData/PORTB.1 missing as you can see per attached images.

Ciao

Leo
- 9th May 2008, 12:39
Acetronics2

A Solution to measure following levels ...

Hi, Wirecut

Pulsin is a command that MUST wait for the leading edge ...

so, if you want to measure, say a PWM signal, you're tempted to Write :

PULSIN Input, 1, Hilev1
PULSIN Input, 0, Lolev1
...

... Am I right ???

But using Pulsin twice will do the Following :

READ correctly the High level ...
RESET it's detection mechanism ( some µs necessary !!! )
WAIT for an incoming falling edge
READ the Low level pulse
RESET it's detection mechanism ( some µs necessary !!! )
WAIT for an incoming rising edge
READ the High level pulse

then it doesn't see the falling edge for the 1st following Low level ( has happend some µs ago !!! )

THEN it will wait for the NEXT falling edge ... wich is the SECOND low level state ...

so, let's resume ...

you read hi state 1, lo state 2, hi state 3, lo state 4

INSTEAD of : hi state 1 , lo state 1, hi state 2, lo state 2 .... etc, etc

TURNAROUND ...

PULSIN Input, 1, Hilev1
RCTIME Input, 0, Lolev1
RCTIME Input, 1, Hilev2
RCTIME Input, 0, Lolev2
...

if using a 4Mhz clock, add 1 unit correction to RCTIME measured values

if using a 20 Mhz clock, add 4 units to RCTIME Measured values

And now, you'll get your values right !!! ... or very, very, very, very close, to be honest !!!

Alain
- 28th June 2008, 12:26
flotulopex

1 Attachment(s)

... little more help needed

Hello Alain,

This is an example of a 13-bit IR pattern I measure on a TSOP4838 receiver module.
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=2701&stc=1&d=121464754 0">

At the start, my prog captures the incoming pattern sent continiously until it determines the starting-bit (first one after the pause between two patterns) and the number of bits (Bit-Count) in the pattern.

I try with this code:

Code:

for Ctr_A = 0 to bit_count rctime p_in, 0, h_Bit[Ctr_A] rctime p_in, 1, l_Bit[Ctr_A] next Ctr_A ' Results are: Bit 00 Low :13795 00 High :350 Bit 01 Low :244 01 High :1253 Bit 02 Low :244 02 High :349 Bit 03 Low :243 03 High :350 Bit 04 Low :244 04 High :350 Bit 05 Low :244 05 High :349 Bit 06 Low :244 06 High :349 Bit 07 Low :243 07 High :350 Bit 08 Low :75 08 High :1 Bit 09 Low :244 09 High :650 Bit 10 Low :243 10 High :350 Bit 11 Low :244 11 High :350 Bit 12 Low :244 12 High :349

This is the code (works fine) I use currently use @ 20MHz and the data I get with PULSIN is:

Code:

for Ctr_A = 0 to bit_count pulsin p_in, 0, L_Bit[Ctr_A] next Ctr_A for Ctr_A = 0 to bit_count pulsin p_in, 1, H_Bit[Ctr_A] next Ctr_A ' Resuts are: Bit 00 Low :1258 'to be multiplied by 2µs (PULSIN res @ 20MHz) 00 High :247 Bit 01 Low :354 01 High :247 Bit 02 Low :354 02 High :247 Bit 03 Low :355 03 High :247 Bit 04 Low :354 04 High :247 Bit 05 Low :354 05 High :247 Bit 06 Low :354 06 High :247 Bit 07 Low :354 07 High :247 Bit 08 Low :655 08 High :247 Bit 09 Low :354 09 High :247 Bit 10 Low :355 10 High :247 Bit 11 Low :355 11 High :247 Bit 12 Low :354 12 High :13797

According to your previous message, I might raise the timings accuracy with RCTIME instead of using PULSIN. Unfortunately, I can't get it to work using RCTIME.

What am I doing wrong, please?
- 28th June 2008, 15:34
Acetronics2

...

Hi, Roger

What I see is you should use 1 time Pulsin ( for the leading pulse) and RCTime for all other pulses ...

AND there's a gentle Mix between H_Bit ( 0 State ) and L_Bit ( 1 state ) ... but may be you did it to match the inverted signal ... ???

should be :

Code:

PULSIN p_in, 0, l_Bit[0] ' measure neg leading pulse RCTIME p_in, 1, h_Bit[0] ' measure time staying High for Ctr_A = 1 to ( bit_count -1 ) rctime p_in, 0, l_Bit[Ctr_A] ' measure time staying Low rctime p_in, 1, h_Bit[Ctr_A] ' measure time staying High next Ctr_A RCTIME p_in, 0, l_bit[bit_count] ' measure time staying Low

"it's been a hard days night ... And I'm working like a dog ..." as told the Beatles !

Regards
Alain
- 28th June 2008, 18:10
flotulopex

Thanks Alain,

I saw the leading PULSIN command in your previous post and tried this already. The result is the same as without PUSLIN but bits are shifted (not important at that time since the bits are sorted lateron).

But why should the preference go for a PULSIN command first?

I notice while using RCTIME, the measurements give slightly lower results (i.e. PULSIN = 355, RCTIME = 349) which looks good.

Any idea why I get a result of 0 or 1 at bit 8 (sometimes bit 7)?

NB: thank you for noticing the variable mix - I corrected already.
- 28th June 2008, 19:42
Acetronics2

Hi,

Quote:

But why should the preference go for a PULSIN command first?

... just to be sure to catch the first pulse ... RCTime is somewhat "out of normal use" for the leading pulse ... result is not guaranteed !!!

Quote:

Any idea why I get a result of 0 or 1 at bit 8 (sometimes bit 7)?

your scoping looks strange ... just at bit 8 !!! ... try to raise the TSOP decoupling caps value and to place a ~ 50 - 100 pF as load to the TSOP output - that could catch possible ns glitches ...

Also take care to have neat 0-5 v levels : the pic Thresold is @ ~1.5 v for TTL inputs ... and Schmitt trigger needs "good" levels ...

Have a nice evening

Alain
- 28th June 2008, 21:45
flotulopex

Merci Alain,

I can't see any change with the decoupling cap and the power is ok. I'll go for some other values and check again.

Quote:

PBP manual: PULSIN normally waits a maximum of 65535 counts before it determines there is no pulse.

It looks to be the same for RCTIME... but as you say, RCTIME has not the same behaviour as PULSIN.

I think, depending on the IR remote type and protocol, I miss the first bit of the pattern.

Is it possible to make PULSIN scan a pin without time limitation (=until a signal is detected)?
- 29th June 2008, 09:17
flotulopex

Okay now

Hi,

To make PULSIN wait "forever" for an incoming signal, I added:

Code:

LOOP1: PULSIN p_in, 0, l_Bit[Ctr_A] ' measure neg leading pulse if l_Bit[Ctr_A] = 0 then LOOP1: led1 = 1 RCTIME p_in, 1, h_Bit[Ctr_A] ' measure time staying High for Ctr_A = 1 to (bit_count - 1) rctime p_in, 0, l_Bit[Ctr_A] ' measure time staying Low rctime p_in, 1, h_Bit[Ctr_A] ' measure time staying High next Ctr_A RCTIME p_in, 0, l_bit[bit_count]

Thanks again for the RCTIME info, Alain. Is there something you don't know about, hein???

Bon dimanche et bonnes salutations hélvètes!!!
- 29th June 2008, 10:17
Acetronics2

Quote:

Originally Posted by flotulopex

Is it possible to make PULSIN scan a pin without time limitation (=until a signal is detected)?

Hi, Roger ...

Of course :

place a waiting loop,

you detect the first pulse with an interrupt: Alain's interrupt is the best here for latency ... as there is nothing to save ! ( RCTime is to use at first here !!! ) and place your RCTime's "gang" in the interrupt stubb ...

( no RETFIE or GOTO needed ! )

then, your display routine ...

Then back to the waiting loop.

now, for better precision ...

you should use

PULSIN
RCTIME
RCTIME
RCTIME
...

instead of a FOR-NEXT Loop ...

Quote:

Is there something you don't know about, hein???

Easy answer is ... WOMEN !!!

True answer is Biology, Medicine and such specialities ... more generally what do not accept a mathematical model !!! ( at least yet ...)

One exception : Horses !!!

Have a nice Sunday

Alain