Thanks for the insight, Bob. I'll try the bypass cap. on the breadboard; might trouble you again if that doesn't help enough! Regards, Anand ----- Original Message ----- From: "Bob Axtell" To: Sent: Sunday, February 08, 2004 10:24 AM Subject: Re: [PIC]: Using The DIYK128 In An ICSP App > Anand Dhuru wrote: > > > Hello folks, > > > > I have a question here; if a PIC is just sitting on the breadboard (not > > powered), and the same 5 signals that reach the programmer's DIP socket are > > connected by an extender to the appropriate pins, would this have a lesser > > chance of working than the true classic ICSP arrangement? > > > I've never had a problem with flash PICs. However, remember that my > method has a bypass cap located right at the device across PIC VCC/GND. > I've always suspected that the cap is critical to proper operation. > > > I am curious because I have had mixed results with this. While this strategy > > works with larger PICs (18 pins and above) it does not seem to work at all > > with 8 pin devices. I have tried using very short, separate cables from the > > socket to the breadboard as well to eliminate any capacitive effects on the > > cable, without success. > > Its because of normal variation in devices. Some simply won't work > without being bypassed, others will. > > > Or are the parallel conductors on the breadboard themselves causing the > > trouble? > > > > No, the programming speed is too slow for such effects. > > > I cant figure this out. For all practical purposes (electrically) the PIC is > > just sitting in the original socket; no crystal, no loads on the clock/data > > lines etc > > But there are ALWAYS capacitive loads, of varying amounts. The ability > of a processor to drive these loads sucessfully depends on the chip's > ability to obtain the instant current it needs to sucessfully drive a > pin. Bypass caps deliver that instanteous current. People are forever > forgetting that CMOS devices, including PIC's, draw current WHEN THINGS > CHANGE STATE. So the bypass cap provides the instantaneous current > needed to do that. PICs running at 32khz draw only a few uAs AVERAGE > current; but when a transition occurs, the requirement is significant, > probably several mA. > > > Incidentally, my observations are based two different hardware; the Melabs > > EPIC and a JDM compatible programmer. > > I don't believe the programmer has any bearing on it. When I first > started doing this, it didn't program properly with the Picstart either. > My scheme works with every programmer I've tried, PICPRO, PICALL, David > Tait, Nixon, all of 'em. It also works for MOST of the PIC16C devices as > long as the +13V supply can deliver the current to program the EEPROM. > > > Anand Dhuru > > Good Luck! > > --Bob > > > > > ----- Original Message ----- > > From: "Bob Axtell" > > To: > > Sent: Sunday, February 08, 2004 2:49 AM > > Subject: [PIC]: Using The DIYK128 In An ICSP App > > > > > > > >> > >>I wanted ICSP enthusiasts to be aware that the DIYKit128 from Peter > >>Crawford at KitsRUs (www.kitsrus.com) works extremely well in my ICSP > >>applications. It is available from Carls' Electronics here in the > > colonies. > > > >>The K128, as well as the K149 and K150, are all designed by Tony Nixon, > >>a member of our esteemed PIClist. Tony specifically states that ICSP > >>will NOT work on his programmer, but in fact a week of testing with two > >>different K128's have proven that with minimal planning it will work > >>very well. The K128 works perfectly w/ 5 different processors (16F872/ > >>6/7, 16F628, and 12F675) mounted on boards. > >> > >>I have enclosed a typical schematic of how I use incircuit programming > >>(Test3.PDF). Note that I isolate the PIC VCC with an SD101 schottky > >>diode. If you use the lowest reverse-voltage available, at the low > >>average currents, the drop is negligible (60-80mv). I use a .1uF bypass > >>local to the chip, to maintain bypassing. Purists will want to replace > >>the diode with a jumper, and that's fine, but when vibration makes the > >>jumper fall out, don't say I didn't warn ya... . > >> > >>The K128 is very tiny, and comes with a standard dual-leaf 40p socket, > >>mounted on top of a tiny black box. You'll need to trim the PCB near the > >>USB connector end, as the intention is for a press-fit at that end. But > >>I used self-tapping screws (#4 x 3/16" Phillips) and that made the > >>assembly very sturdy. > >> > >>Since my applications are 98% ICSP, I used an OLD soldering iron to > >>"drill" a 1/4" dia hole in the case on the end away from the USB > >>connector. I have enclosed my splices onto the 40p connector of the K128 > >>to handle ICSP (K128)_ICSP_connections.PDF). > >> > >>The only hardware gotcha on the K128 is that, while the documentation > >>describes the needed cable as a "standard USB A-type extension cable", > >>in fact it needs a USB A-male to USB A-male, quite a bit harder to find > >>than a simple extension. The rest of the kit is almost pre-assembled; > >>just the thru-hole parts need to be mounted. Very simple, done in an > >>hour. If you are a sloppy solderer, use something to remove the solder > >>droplets and flux. I use mineral spirits, dipping the entire board and > >>scrubbing with a small brush WHILE IN THE SOLUTION (scrubbing the board > >>with the brush away from the solvent might blow the chips). Finally, > >>after quickly air drying, I remove the remaining solvent by putting the > >>PCB in the dishwasher... it works better than anything. If all the water > >>has not been removed, use a hair dryer to get the remainder. > >> > >>The software gotcha is really the old Windows driver snafu. You have to > >>match up the right driver to the right Windows, and the K128's internal > >>PIC (F628) has to match ITS program with the Programmer Software > >>(MicroPro). Once its all together, its a dream. > >> > >>The Micropro programming software works quite well, even has a "voice" > >>mode. Cute for a few minutes then I had to turn it off- it scared the > >>dog and horses. > >> > >>The K128 was exactly what I was looking for. I have pix with an Aries > >>ZIF socket plugged into it (not needed for ICSP) if anyone wants it. > >> > >>------- > >> > >>ICSP Everywhere- a treatise on newer PIC-based designs: > >> > >>In the past, uPs were so expensive that we had to make everything funnel > >>through a single uP. External chips handled everything else. It was a > >>workable solution when the PICs were expensive. But now, a PIC is > >>cheaper than ANY peripheral chip. For example, the F648 can act as a > >>UART with 350 bytes of INCOMING or OUTGOING FIFO ram, for less than $2 > >>ea! NOBODY sells anything like it for less than $10 ea, and because the > >>F648 only needs to do that one task, it can do it at 115kb without a > >>sweat. > > > >>In one application, I had to create a fairly precise (2%) oscillator at > >>38Khz to drive a power inverter when voltage fell below a certain range > >>(voltage divider). I can do it with a single 8pin SOIC PIC that costs > >>less than $.75, plus two resistors and a small cap. I can't even BEGIN > >>to do that cheaper any other way. > >> > >>A project I am doing now has, on a single board, 5 PIC's. All of them > >>are fairly cheap parts, but since they are all doing their jobs IN > >>PARALLEL, the overall thruput is incredible, even at 4Mhz clock speeds! > >>They communicate by way of an "SPI serial port" one master and 4 slaves, > >>all bit banged at about 8kb. AND 4 of them are SOIC14 (150mil) F676's. > >>And yes, each one has a an ICSP programming jack on it. In production > >>the actual jack will NOT be installed; the holes will act as guides for > >>a spring-probe pin assembly; just hold it for a few seconds while it > >>programs. > >> > >> > >>If any Q's let me know, onlist or personally. > >> > >>--Bob > > -- > > Replies: NOTE-Script, EXE,BAT and COM > files will be rejected by server > -------------- > Bob Axtell > PIC Hardware & Firmware Dev > http://beam.to/baxtell > 1-520-219-2363 > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.