Rc signal help

[malc-c]

I've used the 12F675 as an RC switch and it works fine. The only thing is it was programmed in Assembler, and JAL (which I lost the notes on due to a PC crash).

I'm sure its just a matter of getting the timing correct, so the PIC is able to detect and measure the pusle width of every pulse. As I mentioned above, the RX will be sending a pulse every 20ms, which is generally 1 - 2 ms in duration.

[geckogrotto]

Wouldn't holding the stick cause the signal to repeat and therefore catch it at some point?

I have tried and assumed that it would eventually see the signal but never seems to see anything.

I may have to go picaxe as I can't seem to dissect a data sheet.

[malc-c]

Well I just compiled the following and I get flashing LEDs (I haven't got the time this morning to hook up a receiver and test the reading of the PPM signal)

'12F675
@ __CONFIG _INTRC_OSC_CLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF


DEFINE OSC 4
OPTION_REG.5 = 0 ' clock source internal
CMCON = 7
ANSEL=0

Pulselen var word ' Pulselen can be 0 - 255, 100 = 1 ms, 200 = 2 ms
Init var word ' Init used to flash LED
Clear ' set all variables = 0

Input GPIO.4 ' set pin 5 to RX signal

ReadPWM:
PulsIn GPIO.4, 1,Pulselen ' pin 4 - read high pulse length, times out after .65535 seconds
pause 15
If Pulselen < 50 Then GoTo Blink ' no signal -> blink led
If Pulselen > 75 Then GoTo solid ' signal -> Solid led
GoTo ReadPWM

Blink:
For Init = 1 To 3 ' blink led 3 times
High GPIO.1
pause 200
Low GPIO.1
pause 200
Next
pause 1000
GoTo ReadPWM

Solid:
High GPIO.1
pause 3000
Low GPIO.1
pause 200
GoTo ReadPWM
END

The only change I made was to use GPIO.4 and not GPIO.3

EDIT:
OK so I couldn't go out without testing the code to see if it reads the PPM signal.. sorry to say it doesn't detect it

[geckogrotto]

Malc bud when you get back could you try it for me?

I get the blinking light as well that means it is seeing no signal. I can't seem to get it to go solid tho, well actually it does when it feels like it sometimes but not when im pressing the stick.

This has been the problem the whole time just blinks how it wants and seemingly ignores any signal no matter what changes I make to the config or anything.

[geckogrotto]

EDIT:
OK so I couldn't go out without testing the code to see if it reads the PPM signal.. sorry to say it doesn't detect it

Ahh posted edit right as I posted hehe. Yea thats the same thing I get

[Acetronics2]

Hi, Gecko

Some little gags here and there ... but try it !!!


'12F675
@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_OFF & _CP_OFF ' clock source internal
OPTION_REG.5 = 0

DEFINE PULSIN_MAX 2500
DEFINE OSCCAL_1K 1

CMCON = 7 'Tout digital pour 12F675
ADCON0 = 0 'ADC off "
ANSEL = 0
VRCON = 0



Pulselen var Byte ' Pulselen can be 0 - 255, 100 = 1 ms, 200 = 2 ms
Init var Byte ' Init used to flash LED
Compte var Byte

In var GPIO.3
Led var GPIO.1

Clear ' set all variables = 0

TRISIO = %001000

High Led

ReadPWM:

PulsIn In, 1,Pulselen ' pin 4 - read high pulse length, times out after .65535 seconds

If Pulselen < 80 OR Pulselen > 220 Then

Pause 15

Compte = Compte + 1

IF Compte // 16 THEN

Pulsout Led, 10000

ENDIF

Else

HIGH Led

ENDIF

GoTo ReadPWM

END

I'll do better next time ...

Alain

PS: ... breadboard verified .... Yess !!!

[malc-c]

Looking at the manual it states

If the pulse edge never happens
or the width of the pulse is too great to measure, Var is set to zero.

Maybe the the pulsein statement is reaching the 65535 counts before the end of the pulse width and thus is setting the value of pulselen to 0 which will always cause the code to jump to the flash led section.

[malc-c]

Alain,

Now we're getting somewhere... when the TX is powered the LED is constant, when the TX is off (ie no signal beeing transmitted) the LED falshes...

However when the TX is on and the channel that is connected has its state changed (ie gear switch on CH5) nothing happens. Now could this be down to the fact that its detecting a sync pulse and not the actual channel PPM pulse ?

[malc-c]

Well there are no sync pulses coming out of the rx, just a nice train of 1ms pulses at 20ms intervals

[Acetronics2]

Hi, Malc - the - bass - beat - filter - forum ...

I do not understant your question so well ...

When the transmitter is on ( and good link to Rx !!! ) the received channels durations are ALWAYS in the 800 - 2200 µS range ...

WHATEVER you do with your sticks and switches ...

THE ONLY exception is the LM1872 IC coder where pulses can " disappear" from the frame. But I didn't see such circuit in any of our R/C dedicated radios for, at least 30 years ...

I Think you're mixing memory switch and missing ( or wrong ) pulse detector ...

Nothing has to happend on a stick position change, here ...

Alain

[malc-c]

Don't talk to me about base beat filters !!

Let me explain the test rig. I,m using a simple GWS 8ch RX. Ch5 is a straight switched channel on the TX. Ch5 on the RX is connected to the input pin on the PIC. With power applied to the RX and the TX turned on with the switch in one position you get a nice train of 1ms pulses appearing on the PIC input. - There is no mixining involved.

I think whats happening here is we are getting confused over Dan's requirements are. He doesn't want to simply detect the presence of a signal, he needs to detect the change of state of that pulse from 1ms width to 2ms. So maybe the IF/THEN statement should read if pulselen <150 flash LED else LEDS is solid ??

Does pulsein measure the time between positive going pulses, or is it triggered by the positive going pulse, then measures the time in 10us chuncks until it goes negative ? The reason I ask is that if it measures from one positive going pulse to the next then the value will be 20ms (or 2000 counts) and will thus always invoke a "no signal" responce ??