no device detected/how does the detection process work?

hi all, i've recently constructed a pic programmer(pk2 lite). when connected to pickkit2 software, the programmer is detected but i get the error messagr"device not detected". my question is, how does the software able to detect/identify the target pic? what gimmes have to be present? the target pic is a 16f628a. thank you.

Most likely you wired the PIC up wrongly.

Hi,

If doing what John Blue suggests does not cure the problem then run the Tools , Troubleshoot tests to check all 5 lines are connected ok.

I believe the chip type is coded into part of the Pic itself, though some earlier models do not have that feature.

The 628 does have that info, so if it cannot read that info then you probably have a line fault somethere in your build or cable to the 628a.

Assuming you just have the 628 connected by itself and not built into an actual circuit board ?

hi guys, the programmer i built passes all of the troubleshooting tests. however theVdd test gives the message"an external voltage was detected on Vdd pin at 5.0v. as far as the incorrect wiring, iam using aprogramming adaptor board i purchased from FOX delta(PB1) it is designed to be used with pickit2 clones(provided the output connectyor has the proper pinout). i checked continunity of the lines(vpp,vdd, etc. to the target pic this checked o.k.) hope this helps. regards pg

Hi,

When you say it tested out ok, you could see , with the chip out of the socket, the Data and Clock lines toggling High and Low on your voltmeter and see Vpp rise to around 12 to 13v ?

Your programmer board looks fine - assume you have got the LVP switched so pin 10 is Pulled down to 0v by the 10k resistor ?

Have you got another 628 to hand or any other Pic chip you could try incase the original one is fried ?

hi, i didn't actually check it with a voltmeter, but used the software troubleshooting guide. i just tried a 16f84a chip with the same result. yes, the switch was set to pull down the proper pin.

---------- Post added at 20:09 ---------- Previous post was at 18:19 ----------

hi, i think you may be right about the a-a usb cable iam using is faulty. will check and report.

Hi,

You said earlier you checked the continuity of the 5 lines - was that with a multimeter ??

When you did the Hardware Troubleshooting you said that was ok, but now you say you did not use a volt meter ?? - you cannot really check the functionality of the Pk2 to the 628A / prog board without checking the voltages as detailed. The 12v on Vpp being very important, and the toggling of D and CLK between 0v and 5v really prove the wiring is correct.

Not quite sure what/which you mean by the "software troubleshooting guide."

Without doing those tests properly you are really working in the dark.

As the PK2 seems to be working with the PC ok just need to check two other points, is the pc a desk or laptop ? and how long are the connecting wires between the PK2 output and the programmer board, more than 6" of unshielded cables and you can have such problems.

hi wp100, the cable length is 18". (software troubleshooting guide) thats microchip pickit2 v.2.61. pic programming system. i agree, i might have posted prematurely. i have some more trouleshooting to do. will post back. thanks.

Hi,

the cable length is 18"

Click to expand...

Well if thats the cable from the PK2 output socket to the Programmer board then while you will get good results from the static tests as soon as it tries to communicate with the pic chip in its normal high speed the signals just 'get lost'.

Shorten it to just an inch or two and see it that works.
Have found cables over 6" long will cause such problem.

If you can download the PK2s OS from PK2 2.61 then doubt there is much wrong with your USB PC to Pk2 cable

hi wp100, the problem is when i printed the pcb pattern i screwed up the usb connections on the programmer board. how that happened i don't know. i'am going to hardwire the connector that goes to the usb port on the pc to the pickit2 lite. one question. on your schematic you have pin 2 on the usb connector going to pin 16 of the 18f2550 & pin 3 going to pin 15. is this correct?

Hi,

Yes you are right, there is an error on my schematic, it should be USB pin 2 to Pic pin 15 -D and USB pin 3 to Pic pin16 +D.
Even Bluerooms schematic has got the +D and -D mixed up as well.
See Microchips schematics in the Pk2 user manual.
USB pinout and wiring @ pinouts.ru

If you had those connections the wrong way around you would not have been able to run the program PK2 2.61, so your pcb will be correct.

hi, condition same(microchip pickit2 v.2.62 does not detect target pic). took the following readings using tools-troubleshooting. pin4mclr--11.8, pin 12--.29/00, pin13--1.48/.00, pin14--4.94v. what should pin 12 & 13 be when toggling?

---------- Post added at 15:05 ---------- Previous post was at 15:03 ----------

hi, the above readings taken with DMM.

Hi,

Have just hooked up a 628 chip, think it should be similar readings to the 628A chip. Do not worry about things being 0.1v or 0.2v different to mine.

The Mclre Vpp of 11.8v you have is good, but do test the Mclre On and Off in the same section - ON should read 0v OFF should read 4.7 -5.0v

When testing Dat and Clock with the 628 chip in and using just the HI and LO switches I got Dat 0.9v ON 0v OFF; CLK 0.75v ON 0v OFF.
The same test but with the chip removed I got D 4.2 / 0 ; C 4.8 / 0

Toggling is really for a scope to check the waveform, you will not get a sensible voltmeter reading.

Double check all your readings particularly the D and C pins incase you have them crossed over by mistake.

You sound very close to getting things going...

hi, my readings follow: MCLR on 0v--off 0v. DAT on 1.47v/0v. CLK on .29v/0v.------chip removed: DAT on 1.47v/0v. CLK on:.29v/0v. same as with chip in circuit.

---------- Post added at 19:41 ---------- Previous post was at 19:03 ----------

hi, the readings in my previous post are incorrect. the correct readings follow: MCLR on--11.8/0. chip in: DAT--3.00/0. CLK--4.85/3.00. chip out: DAT--4.85/.58. CLK--.58/0. OY, being 73 is a bitch!

Hi,

Not your age, just that you have chosen what seems an easy project, which it can be, but when it goes wrong its a sod for the micro novice to sort out.

Some of your readings look ok then others do not.

The order of importance is first Vdd at 4.7 to 5.0 v - which it is.

Second Pin4 Mclre /Vpp - in that test you must achieve the 3 states of 12v for Vpp, 5v for Mclre Off, and 0v for Mclre ON - if not then the programmer cannot work. - Chip in or out , it should read the same.

Third - the Clk and Data lines., the figs for the Data seem reasonable but the clk looks wrong.

As you are so close to it working and have used a pcb my suspicion is that you have got the transistors orientation wrong.
This might simply be that you have placed them in wrong, it can be so easy to view the parts say from the top when it should be from the bottom etc. but probably it might be that the diagram you used was not that for the transistors you purchased.

Although you would think a BC557 ( or whatever) is the same pin out around the world, different manufactures do sometimes use different pin outs, so you need to check your supplier / transistor manufacturers data sheet for the ones you have and then check if that matches with the pcb layout.

Let us know how you get on...

hi, actually iam using 2n3904/06 transistors, EBC. the orientation seems correct. i'll keep checking, if nothing else, i'am persistent. regards pete g.

Hi,

Just been checking those transistors, all manufacturers here seem to have the same pinouts.

Can see the PCB board you used but not the component mask as I do not have Eagle loaded.

The pcb does look quite small and the joints very close so apart from correct orientation it would be easy to leave two connections bridged by solder etc.
Try running the back edge of a scalpel blade or similar between the pads/joints as even the solder flux can contain bits of solder that will short things out.

Sometimes the pcb just gets too messy and it can be better to start again with new transistors - even using a piece of strip board instead of a pcb - works fine for me.

hi, yes, those transistors pretty much have been standardized. your suggestion of starting over, is starting to have a lot of appeal. i like to use pc boards because in my case i don't make as many wiring errors.it would be helpful if a componet placement layout was available. BTW nice job on the pictured programmer. i was thinking that since the subject programmer is so basic, it might be the model for a tutorial on how usb programmers work. maybe a transistor by transistor explanantion, including voltages/waveforms. as far as i can tell the transistor orientation of my programmer seems correct. assuming all else is good, what would my voltage reading indicate/pointing towards the problem? incidently, thanks for all your input. pg

Hi,

So you are saying there is no component silk with that pcb design - could easily lead to errors if there is not.

Might be worth searching this forum as there are many many posts for the Pickit2 lite and think I have seen a few other pcb layouts you could use - assume its easy for you to do your own boards.

I built my 'Lite as just as backup to my purchased Microchip Pickit2 - which I still recommend as the best thing around for the money - though can understand folk wanting to build their own.

Sure Electronics do a really good Zif board with 3 zif sockets to compliment the Pk2 / Lite

As things worked fine for my build I have not much experience on troubleshooting other than the inbuilt tests in the PK2 program.

As you can do those tests, it proves your 2550 is running, you have 12v from the Vpp pump which is a frequent problem area when folk do not use the right parts, so it would seem reasonable to suspect the transistors and associate resistors that switch the 2550s output signals.
Have not actually scoped those 2550 output pins to see the levels /waveforms.

The Data and Clock lines are direct drive from the pic via the resistors and the Vpp /Mlcre functions are controlled by the 3 transistors, so thats the area to concentrate on and you should be able to test the 3 voltage states I mentioned earlier - though as you know after so much messing around a clean rebuild with new tansistors and resistors can be the better option.

Just as a final check on your 2550, if you start Pk2 up then go to Tools, Download PK2 operating system, does that work ? - it should be able to ask for and find its program pk2v032300.hex in the Microchip / Pickit2 folder.
Takes about 30 secs to download, install and verify.

hi, i think i'am going to take your suggestion and try to find a site that has the pcb/parts overlay available. if thats not possible, then i'am going to try my hand at making the programmer on perf board. will post back on my progress. again, thanks a bunch for all your help. regards pg.