Guest NickRP Posted April 22, 2003 Report Share Posted April 22, 2003 Hello guys,I have problems very similar to ones described a few weeks ago. The difference is that I know that my JDM does not read the PIC correctly, since I tried previously programmed devices. If the IO delay is 1, read returns all 0s, if it is more than 1, read returns 3fffs. All the time, no exceptions.My JDM is made of newpic22.gif schematic, from JDM site. I use IC-prog, as well. The voltages measured are:1) Enable Vcc: Vdd=5.36v.2) Enable /MCLR: /MCLR=11.5v and starts falling as the multimeter draws current that charges cap.3) Enable Vcc, Enable /MCLR: Vdd=5.36v, /MCLR=13.38v.4) Enable Clock: RB6=6.06v.5) Enable Clock, Enable Vcc: Vdd=4.8v (falling), /MCLR=10v (falling), RB6=4v (falling) [ guess those values are going to fall til the capacitors are fully charged, but I got tired of waiting)6) Enable Vcc, Enable /MCLR, Enable Data Out: RB7=4.90v.7) Enable Vcc, Enable /MCLR, Enable Clock, Enable Data Out: RB7=4v (falling).8) The data in signal follows Data Out regulary.Tonigth I added an extra diode in series to 5.1 Zener, so all voltages are about .6v higher... No good..Please help.. this is for my end term project... and I will be in trouble if I cannot burn this PIC...Nick. Quote Link to comment Share on other sites More sharing options...
Guest sstandfast Posted April 22, 2003 Report Share Posted April 22, 2003 Hey Nick,For a simple circuit those JDM's can be a real pain to get to work correctly. It is strange to me that when you performed your tests that your voltages were all falling. An unstable voltage on RB6 is understandable and expected but the other voltages should remain fairly consistent.MCLR should remain between 13V and 14V.VDD should be hanging pretty close to 5V and the same with RB7; 5V.These values should not fluctuate hardly at all. So check to make sure that you have all your components stuffed correctly, you may have a diode in backwards or something because it seams that you have a voltage leak somewhere. Also check for short circuits somewhere, check under the DB9 and make sure that you haven’t accidentally bridged two pins together.Did you build this on vector board or did you make a PCB for it? if you built it on vector board I suggest that you make a PCB for it, it simplifies things greatly. They are really easy to make and only take a couple of hours. The PCB artwork for the JDM can be found on Thorsten's web page and for instructions on how to make your own PCB just click here: http://watt.lab.eese.bee.qut.edu.au/~n4403584/pcb.htmOther that that the only other advice I am qualified to give is check all your connections and compare your board with the schematic several times. You'll figure it out.Good luck!Shawn Quote Link to comment Share on other sites More sharing options...
Guest NickRP Posted April 23, 2003 Report Share Posted April 23, 2003 Hey,The problem is solved... I was stupid enough to tie LVP to Vdd, since I was copying the old JDM schematic... At the same moment I corrected this, it started reading and writing flawlessly...Now, concerning the falling voltages... I have double(²) checked the circuit (on the vector board). As you suggested, I am going to build one more programmer, on the PCB... Thank you very much for help!!!!Nick. Quote Link to comment Share on other sites More sharing options...
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