Better understanding PULSIN

[Wirecut]

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

[mackrackit]

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

pulsin IR_Sensor,0,IRpuls_len(BitCount)

Change the "0" to "1" to read the high pulse.

[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

[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?

[Wirecut]

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

[Acetronics2]

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