Post by thread:[PIC] [EE] Problems with NOPPP and PIC16F84A

Byron A Jeff wrote: > > What voltage does the serial port generate? All of the serial port designs > were designed to work with true blue EIA-232C serial ports. PCs haven't > had > such serial ports in close to 10 years. Many PC serial ports only generate > voltages of 0 to 5V, with some generating voltages as low as 3.3V. > I'm not using the serial port. The NOPPP design interfaces to the parallel port. Not that that really matters. Byron A Jeff wrote: {Quote hidden}> > Again what's the Vpp voltage at PIC socket. If you're using 16F84A's and > that > voltage isn't 13V +/- 0.5V then it isn't going to program. Also IIRC the > 16F84A has a whopping huge programming current. I checked out the > programming > specification. 50 mA! OUCH! > > No serial port in the world is going to provide 50 mA of current at 13V. > > If you're serious about pursuing this design, I'd advise adding a external > 13V power supply to provide Vpp. > My circuit uses and external pc power supply to send 12v to !MCLR, controlled by the parallel port via a transistor, and the 5v for the chip's voltage input. I thought I had read that the '84A needed about 12v on !MCLR, but perhaps I was mistaken and I need something more powerful. When you say Vpp, are you actually referring to !MCLR? Because every programmer design I've ever seen applies 5v to Vpp to power the chip and uses the higher voltage purely to trigger the chip into high-voltage programming mode on !MCLR. Perhaps I'm misunderstanding something, but perhaps not. I'll attempt applying a higher voltage to !MCLR when I get back to it, but I do believe I already tried with a wall-wart outputting about 17v and the results were the same, however I may have just tried this with the COM84. I can't remember. I'll verify this when I get back to the project. -- View this message in context: www.nabble.com/-PIC--Problems-with-NOPPP-and-PIC16F84A-tf3330790.html#a9277465 Sent from the PIC - [PIC] mailing list archive at Nabble.com.

On Fri, Mar 02, 2007 at 01:10:40PM -0800, Joseph Marlin wrote: > Byron A Jeff wrote: > > What voltage does the serial port generate? All of the serial port designs > > were designed to work with true blue EIA-232C serial ports. PCs haven't > > had > > such serial ports in close to 10 years. Many PC serial ports only generate > > voltages of 0 to 5V, with some generating voltages as low as 3.3V. > I'm not using the serial port. The NOPPP design interfaces to the parallel > port. Not that that really matters. Actually it does. Sorry for the mistake. Michael covers two of the major issues using the parallel port: port voltage and cable crosstalk. For cable crosstalk In his README he suggest using a cable of 3 ft or less. I agree. Even when you get a statically correct reading on the programmer, when the bits start flying, it can get messed up. The second is port voltage. The NOPPP was designed at a time where parallel ports actually output 5V for a high signal. Virtually no parallel port does that today. Most output 3.3V max which isn't enough to trigger a high reading on the PIC. The revised schematic in noppp-x.gif addresses the issue by using pullups with diodes. One other thing I see is that for that schematic Michael has a 2.2K pullup between the 13V power supply and MCLR. That only provides 5 mA of current which is 10 times less than needed. Substitute a 220 ohm resistor there instead. {Quote hidden}> Byron A Jeff wrote: > > > > Again what's the Vpp voltage at PIC socket. If you're using 16F84A's and > > that > > voltage isn't 13V +/- 0.5V then it isn't going to program. Also IIRC the > > 16F84A has a whopping huge programming current. I checked out the > > programming > > specification. 50 mA! OUCH! > > > > No serial port in the world is going to provide 50 mA of current at 13V. > > > > If you're serious about pursuing this design, I'd advise adding a external > > 13V power supply to provide Vpp. > > > > My circuit uses and external pc power supply to send 12v to !MCLR, > controlled by the parallel port via a transistor, and the 5v for the chip's > voltage input. I thought I had read that the '84A needed about 12v on !MCLR, > but perhaps I was mistaken and I need something more powerful. 12V is the bare minimum. 13V is nominal. > When you say Vpp, are you actually referring to !MCLR? I'm referring to the 13V programming voltage that must be applied to the MCLR pin. The programming voltage isn't a reset signal, which MCLR (Master Clear) indicates. It's really two different functions (reset and programming) assigned to a single pin. > Because every > programmer design I've ever seen applies 5v to Vpp That's Vdd, not Vpp. > to power the chip and > uses the higher voltage purely to trigger the chip into high-voltage > programming mode on !MCLR. That's Vpp. > Perhaps I'm misunderstanding something, but > perhaps not. I'll attempt applying a higher voltage to !MCLR when I get back > to it, 13V. No more than 14V or you'll potentially fry the part. > but I do believe I already tried with a wall-wart outputting about > 17v and the results were the same, however I may have just tried this with > the COM84. I can't remember. I'll verify this when I get back to the > project. Keep at it. Also I would seriously advise you to heed my advise about using an updated part. The 16F84A limitations will lead to poor design habits out of necessity. BAJ

>One other thing I see is that for that schematic Michael has a 2.2K pullup >between the 13V power supply and MCLR. That only provides 5 mA of current >which is 10 times less than needed. Substitute a 220 ohm resistor there >instead. This could very well be the thing that's giving me problems. I'll go back through and check all of my amperages to see what kinds of values I'm getting and try replacing that resistor. I appologize for all of my stupidity on this subject because I have almost no real experience in working with electronics, but I do so enjoy jumping into the deep end, which I realize doesn't really constitute a right for me to ask someone else to pull me out, so thank you once again for your patience and helpfulness. I'll try and pass it on. {Quote hidden}>> Because every >> programmer design I've ever seen applies 5v to Vpp >That's Vdd, not Vpp. >> to power the chip and >> uses the higher voltage purely to trigger the chip into high-voltage >> programming mode on !MCLR. >That's Vpp. *slap to the forehead* d'oh! I'm really sorry, I knew that. Don't know what I was thinking. My appologies. So yes, once I can find another 9v for my multimeter I'll address these issues and, if I'm going to report anything, I won't report until I can report sucess. Thank you again and, again, my appologies for inconviniencing you with my noobish ways. -- View this message in context: www.nabble.com/-PIC--Problems-with-NOPPP-and-PIC16F84A-tf3330790.html#a9289482 Sent from the PIC - [PIC] mailing list archive at Nabble.com.

Joseph Marlin wrote: {Quote hidden}>> One other thing I see is that for that schematic Michael has a 2.2K pullup >> between the 13V power supply and MCLR. That only provides 5 mA of current >> which is 10 times less than needed. Substitute a 220 ohm resistor there >> instead. >> > > This could very well be the thing that's giving me problems. I'll go back > through and check all of my amperages to see what kinds of values I'm > getting and try replacing that resistor. I appologize for all of my > stupidity on this subject because I have almost no real experience in > working with electronics, but I do so enjoy jumping into the deep end, which > I realize doesn't really constitute a right for me to ask someone else to > pull me out, so thank you once again for your patience and helpfulness. I'll > try and pass it on. > > >>> Because every >>> programmer design I've ever seen applies 5v to Vpp >>> > > >> That's Vdd, not Vpp. >> > > >>> to power the chip and >>> uses the higher voltage purely to trigger the chip into high-voltage >>> programming mode on !MCLR. >>> > > >> That's Vpp. >> > > *slap to the forehead* d'oh! I'm really sorry, I knew that. Don't know what > I was thinking. My appologies. > > So yes, once I can find another 9v for my multimeter I'll address these > issues and, if I'm going to report anything, I won't report until I can > report sucess. Thank you again and, again, my appologies for inconviniencing > you with my noobish ways. > > No apology is ever needed here. --Bob

On Sat, Mar 03, 2007 at 12:42:18PM -0800, Joseph Marlin wrote: > > >One other thing I see is that for that schematic Michael has a 2.2K pullup > >between the 13V power supply and MCLR. That only provides 5 mA of current > >which is 10 times less than needed. Substitute a 220 ohm resistor there > >instead. > > This could very well be the thing that's giving me problems. I'll go back > through and check all of my amperages to see what kinds of values I'm > getting and try replacing that resistor. I appologize for all of my > stupidity on this subject because I have almost no real experience in > working with electronics, There's no stupidity here. That would be insisting that you did everything right so it's Microchip's fault or something like that. The only part if you education I'll keep pounding on is upgrading to a newer part. In the 16F family I'd suggest the top end parts with the nanowatt features and the most memory which is the 16F88 for the 18 pin package and the 16F886/16F887 for the 28/40 pin packages. It'll help you a lot in the long run. > but I do so enjoy jumping into the deep end, which > I realize doesn't really constitute a right for me to ask someone else to > pull me out, so thank you once again for your patience and helpfulness. I'll > try and pass it on. No problem. Hope that it works for you. {Quote hidden}> > >> Because every > >> programmer design I've ever seen applies 5v to Vpp > > >That's Vdd, not Vpp. > > >> to power the chip and > >> uses the higher voltage purely to trigger the chip into high-voltage > >> programming mode on !MCLR. > > >That's Vpp. > > *slap to the forehead* d'oh! I'm really sorry, I knew that. Don't know what > I was thinking. My appologies. Again no need to apologize. Just clearing up a misunderstanding. > So yes, once I can find another 9v for my multimeter I'll address these > issues and, if I'm going to report anything, I won't report until I can > report sucess. Thank you again and, again, my appologies for inconviniencing > you with my noobish ways. Actually report even if it's not successful. Homebrew programmer debugging tends to be an interative process. BAJ