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About Xygax

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    RC-Cam Visitor
  1. Ok i understand that so move it from a 508 to a 629 or similar that has a capture module. Sample an incoming video signal using the frame pulse and interval with the capture module and hold off the rest of the code until it senses a frame period too long or loss . Then it could replace the signal seamlessly using an analouge switch. After it it sees the return of the frame pulse and period (one or two whole frames 40mS) then it can switch back to the incoming video signal. The circuit is quite simple. Feed the composite video into the comparator useing a low reference voltage (so it only grabs the frame sync) and feed this out from the comparator into the capture module. This is alternatly configured to measure the frame pulse width and period. if all is ok you get a green light and the video switch is held towards the normal video input. in event that either the frame pulse is to long / short then the value comiing back from the capture module not match a good pulse and this would start the sync generator and at the same time flick the selection switch from normal to artifical thus keeping the dispaly alive for a frame or two whilst the normal signal restores. The capture is interupt driven so the frame measure is late by the int latency period of say 10uS (or 2 lines) and this isnt normally a problem as the replacement signal isnt normally generated. In the event that the replacement signal is present then the INT is disabled except in the frame sync pulse where it firstly measures the period of the incoming sync to determine its presence prior to switch back to normal when it measures width and period. Probable result using this method is a black screen for the duration of the missing sync +1 frame and then restore to normal with a dirty lock (frame roll or slide) Sorry for the rambling but i can see a soulition but at the moment no time to code it... Steve
  2. I have been thinking about this and did a little research http://www.atv-projects.com/50p_SPG.html This is a litle generator that can be used to prove either way whether the sync is the 'keep alive' signal that blocks the blue screen and if so then there should be a way of remodeling the code on this chip to sync to an incoming sync pulse on one of the spare pins. Ok it may meen using a chip that can run at 8Mhz to make the timing work but its entirly posible to use a little micro to generate a phase locked sync signal and at worse you will see a frame roll as it locks this may be preferable to the 'blue screen' Steve
  3. This is a theroy rather than a proven way foward... I think that most monitors monitor the sync pulse and this is the key to them staying on (computer monitor is clasic esample) when the sync disapears the monitor starts the shutdown / loss of signal process. This can be reasonably simple to prove. Take a monitor that uses RGB + Sync... remove one at a time the r...g...b and look for the black screen... or take away the sync and see the blue screen... I remember the device that generated sync pulses was a ZNA134 or later a ZNA234 this could be locked to the incoming sync so that it free runs in the event of signal loss then at the point of signal return you would at worse get a frame roll as it sync'd should help cut down the ammount of time its off beacause of lost signal and hopfully prevent teh blue screen of death...! I dont know if they are available now but it could be replicated with a micro... Steve
  4. Steven: The lowest cost option is going to be the pickit 2 or 3 MAplins or microchip direct STeve (in brstolium)
  5. The conventional way to run a series LED stack is a small switch mode (30w from 12v is a flyback) these are normally run in current mode with upper voltage limit about 0.3-0.5v above the upper led stack voltage. probably simplest with a 3842 and an irf530 and a quality 10 A shoktty diode would be about right for this type of application it would reject the varation in bike battery voltage completly and provide a constant current to the load from 9 - 16 v and they are 80+% efficent ... Steve
  6. OK. Make the comparator -ve the RC input and put aabout 2.5v from Vref. (that coveres the 3.3v outputs from some RX's) connect the comparator out to a pin and then via a resistor (1 k ish) to the capture compare input. (you can also put a switch to -ve here if you need a program input) The comparator removes any rubbish on the edges and is a universal level converter. so at the input to the ccp module you have a good clean 5v signal (a bonus is you can also put a scope on it to see when you havent turned the Vref on !!!) I know it uses up two pins but is a good soulition as the comparator is free running and it gives accurate 5v input to the capture (CCP module) Below is the capture ISR that gives a 16 bit result in Us Steve ;------------------------ INTERUPT PROCESS-------------------------------------- TMR1_ISR ;------------------------ TMR1 free running with an underflow counter --------- BCF PIR1,TMR1IF ; CLEAR INT FLAG bsf Tick return CCP1_ISR ; --------- Edge detect and constant save--------- ; --------- INVERTED SIGNAL----------------------- bcf PIR1,CCP1IF ; re enable capture btfsc CCP1CON,CCP1M0 ; check Falling edge goto Falling_edge ; yep then sort movf CCPR1L,w ; movwf Leading_1 ; and store movf CCPR1H,w movwf Leading_1+1 bsf CCP1CON,CCP1M0 ; set for raiseing edge capture bcf Pulse_1_done ; only half done return Falling_edge bcf CCP1CON,CCP1M0 ; set for rising edge capture movf CCPR1L,w ; grap captured value movwf Capture_1 movf CCPR1H,w movwf Capture_1+1 ; and store bsf Pulse_1_done SUB16 Capture_1, Leading_1; do maths result in Us in capture Return
  7. Just a note of thanks for everybodys input on this project.... Built and bastardized... Alternative application time.... Wireless sim connection for JR / Spektrum. There is a minor change... C1 needs to be 47n not 22n... (the leading pulse is too short to register reliably with the Phoenix dongle) and the micro isnt required just link pin 1 and 5 Has been tested with an AR6100e and a DX6i so far but i'm sure DSX9's and so on will work OK.... Thanks Steve
  8. Try this one http://www.designsoft.com.au/ahome/rc/PIC-LMA/lma.html Steve
  9. Guys: I use a comparator and voltage ref module on a 627 or 675 and this cleans up the incoming signal (and leaves it inverted) then feed this out and then back in to the capture pin. This will give a 1Us accuracy when trigged from TMR0. Because its not reliant on latency within the interurpt then its repeatable. Just make sure that you manage the rollover of TMR (the reference for capture) properly or it will glitch... STeve
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