A very very very strange problem-Urgent help needed please!

[FromTheCockpit]

Hi, I am having RF modules operating a switch only when button is pressed AND as long as the button is pressed on the Tx. I am using 12F635.
Problem is that the PIC LATCHES when I go beyond lets say 5 meters. When I come near and press the second button on the Tx the latch opens and it starts behaving fine.
RF Modules have a range of greater than 100 Meters. I can't figure out WHY is this happening?
I need urgent help on this please. Thanks

main:
Receiver code
serin gpio.2,N2400,100,stop,["p34"],b
if b=24 then gpio.1=1
if b=54 then gpio.0=1
goto main

stop:
gpio.1=0
gpio.0=0
goto main

Transmitter code
main:
if gpio.0=1 then
serout gpio.5,N2400,["p34",54] : pause 5 : low gpio.0 :  endif
if gpio.1=1 then
serout gpio.5,N2400,["p34",24] : pause 5 : low gpio.1 : endif

[Melanie]

These are actually Data certified 2400 Baud Transmitter/Receiver Modules, or they're just plain junk Tx/Rx modules whereby you are simply keying the carrier at 2400 Baud and hoping that the receiver will attempt to replicate what's happening at the Transmitter once the signal dips into noise and the other rubbish floating about?

[Acetronics2]

Hi,

Some of our R/C sets do not dare to work when too close to the transmitter ...

Saturated HF input stage of the receiver ... locked decoder.

= oversensitive devices ...

Low priced receivers with a "simply engineered AGC Stage ...

Alain

PS:

Urgent help needed please

I do not know why, but these words always make me laugh ... like the word " problem " ...

[Bruce]

If your transmitter switch pins are inputs, and a switch press applies Vcc to a pin, why are
you flipping these pins to outputs after a switch press and setting them at ground?

[FromTheCockpit]

If your transmitter switch pins are inputs, and a switch press applies Vcc to a pin, why are
you flipping these pins to outputs after a switch press and setting them at ground?

Point noted, Thanks. I will remove "low..." statements from the code.

Alain: Do you mean problem is with RF Link? as they do work fine as per my post above.

My config Fuses are set as follows:
WDT_ON
PWRTC_ON
MCLR_OFF
BOD_ON
IESO_OFF
INT_OSC-NOCLKOUT

and other configuration is:
intcon=0
cmcon0=7
TRISIO=%001100
GPIO=0

I have checked that with my toggling switch, once you go out of range receiver PIC does not respond as soon as you walk within range it starts working fine.

BUT, with this momentary design, after the PIC latches I checked the voltage on Rx pin and it is fluctuating as other signals are in the air as well. I also found out that once PIC latches there could be one sure shot way of making it work again, which is power reset and the other not so sure shot way is press the second button on the transmitter which sends a different code. BUT again this hangs the PIC as soon as you go few meters away.

[Macgman2000]

Be careful that the module you select has a data in = data out feature. Some low cost modules need to have a "balanced" data stream in order to work well.

One of the symptoms is reduced range, the closer you are the more likely the data makes it through the demod stage. The further out you go the more you get DC offsets that creep up and cause the demod to hold states longer causing bit distortion. You should be able to see this on a scope.....latch the tx in continuous transmit at 30m and look at the output of the RX.

Nick

[FromTheCockpit]

Be careful that the module you select has a data in = data out feature. Some low cost modules need to have a "balanced" data stream in order to work well.

One of the symptoms is reduced range, the closer you are the more likely the data makes it through the demod stage. The further out you go the more you get DC offsets that creep up and cause the demod to hold states longer causing bit distortion. You should be able to see this on a scope.....latch the tx in continuous transmit at 30m and look at the output of the RX.

Nick

Thanks, Reading your post I am assuming that if I make the following changes to the code, it will help to balance the data stream and allow sufficient time to the receiver to process previous data before new one is thrown in:

receiver code:
main:
serin gpio.2,N2400,250,stop,["p34"],b
if b=24 then gpio.1=1
if b=54 then gpio.0=1
goto main

stop:
gpio.1=0
gpio.0=0
goto main

Transmitter code
main:
if gpio.0=1 then
serout gpio.5,N2400,["p34",54] : pause 50 : endif
if gpio.1=1 then
serout gpio.5,N2400,["p34",24] : pause 50 : endif

Have I understood the point right?

[FromTheCockpit]

These are actually Data certified 2400 Baud Transmitter/Receiver Modules, or they're just plain junk Tx/Rx modules whereby you are simply keying the carrier at 2400 Baud and hoping that the receiver will attempt to replicate what's happening at the Transmitter once the signal dips into noise and the other rubbish floating about?

They are just normal Rx/Tx with stated range upto 150 Meters. They actually work very well upto 100 Meters when I use it for toggling pins high or low (my other kind of switch- Tx button pressed once, receiver switches on somthing, Tx switch pressed again - receiver switches it off) at the receiver. But dont know why the receiver PIC latches up in this kind I am making where it should only stay on untill TX is pressed.