Working 35 inch ICSP cable.

[3v0]

In the thread "PGD PGC Crosstalk" I posted the direction on how to make a longer then normal ICSP cable without and additional parts. I flipped the center 8 conductors on each end to isolate PGC and PGD from each other.

 

[Krumlink]

Wow! What programmer were you using?

 

[3v0]

Wow! What programmer were you using?

Junebug. It was hard to program the walter robots with the short ones.

 

[blueroomelectronics]

35" how big is walter?

 

[3v0]

35" how big is walter?

Not all that much larger then a mongoose. Maybe twice as tall and few inches longer.

EDIT:
I constructed the cable to see if rearranging the conductors would make it better. I am fairly sure a cable 35 inches long would not work without the twist. Proof of concept.

 

[eblc1388]

Tried that already in the past.

You are still 4.6 inch short to break my record at 100cm = 39.6" in year 2005.

 

[3v0]

Tried that already in the past.

You are still 4.6 inch short to break my record at 100cm = 39.6" in year 2005.

Drat. Did you find it to be reliable.

 

[eblc1388]

Back in Y2005, there were a lot of discussions on why some DIY built PIC programmers doesn't work and one of the claims was that the connecting cable is longer than 10".

The other claim was that the Vpp must be 13V or higher.

It had become ridiculous that some users were advising others that a 10" cable is too long and will not work. They also proposed cable length of 6" or less. This was measured from the printer port to the programmer or from the programmer to the target PIC.

The experiment I did was to use 1 meter connecting wires and low Vpp voltage of 12V to show that both claims were not necessarily true.

Of course it is not reliable but most PIC programmers doesn't work had inherent hardware problems and long cable is the least worry of them.

 

[3v0]

Did your long cable have the conductors rearranged as in my OP? Or did you just make a longer cable.

 

[eblc1388]

That thread is here:

PIC programmer & WinPicProg: my findings

 

[3v0]

You used 5 loose wires and I used a ribbon cable.
The crosstalk problem has got to be greater in the ribbon cable.
Just the same that was a good bit of debunking.

EDIT: with the newer chips they are clocking the data faster.
Your image:

**broken link removed**

 

[eblc1388]

You have a point there. I went a step further.

I have always designed my circuits to use a 6-way ribbon cable, even on all PIC programmers, the first day I started to use PIC. I know that its not standard so I won't recommend anyone to do as I do.

The reason is to have a GND wire between PGD and PGC. Never have any problems of crosstalk.

 

[3v0]

You have a point there. I went a step further.

I have always designed my circuits to use a 6-way ribbon cable, even on all PIC programmers, the first day I started to use PIC. I know that its not standard so I won't recommend anyone to do as I do.

The reason is to have a GND wire between PGD and PGC. Never have any problems of crosstalk.

I have been harping about this for a while. My first suggestion was to use every other line as gnd on the 2x5. People did not like this because if you plugged it in backward everything is shorted to ground. I understand where they are coming from.

This solution swaps the VPP and PGC wires just prior to entering the IDC connectors on both ends. This places both VDD and GND between PGC and PGD which should provide good isolation. The cable is not hard to make and it can be used without modifying the programmer or target.

 

[eblc1388]

I have a bitter experience to share with you.

The last time I split up an IDC cable and rearrange the cable cores to suit my need cost me a lot of grieves. I'll never do that again.

I separated the ribbon cable cores, rearrange the wire order and crimp, it looked fine on the outside. Unfortunately(or fortunately, by another word) one of the connecting pins had pierced the insulation of adjacent wire giving an intermittent short circuit when I move the cable.

I was wondering why my programmer is working 9 out of 10 trials.

 

[Pommie]

Now I think about it, I have not had any problem with crosstalk. My typical cables are around 12". Why would you want a longer cable?

Mike.

 

[3v0]

Now I think about it, I have not had any problem with crosstalk. My typical cables are around 12". Why would you want a longer cable?

Mike.

This is too long but it covers the motivation.

I would have been happy with a slightly longer cable. The short ones are bothersome at times.

When there is a problem with an iffy programmer people ask is if the cable is greater the 6 inches. Microchip says to keep the cable as short as possible but site reflections as the reason. In-Circuit Serial Programming™(ICSP™) Guide. The guide talks about latchup which I have seen now and again. We had one Friday with a short cable. There is a problem with the cable design as it exists. Keeping it short is a band-aid that works most of the time.

I am not an EE but the placement of PGC and PGD together bugged me from day 1. I figured crosstalk was the problem.

Earlier I found one site that talked about crosstalk.

PGD to PGC Crosstalk

While this is really another circuit constraint, this issue is so unintuitive, little known, poorly documented, but serious that it deserves its own section.

The standard Microchip cable unfortunately puts PGD and PGC on adjacent lines. Since this is a flat cable, this can and does lead to crosstalk between the two in some cases. For writing to the target, the programmer drives both lines. In that case a little low pass filtering can be applied by the programmer to soften the edges and reduce the coupled amplitude on one line from an edge on the other...

I was looking at preventing crosstalk by isolating the signals. The solution does not require modification of the target or the programmer.

Given what Microchip says about ringing/reflections I am not sure I am on the right track. On the other hand it could be that an engineer at microchip blamed the problem on reflections when it was crosstalk or both.

Until the real world proves me wrong I have a working cable.

 

[Funny NYPD]

Back in Y2005, there were a lot of discussions on why some DIY built PIC programmers doesn't work and one of the claims was that the connecting cable is longer than 10".

The other claim was that the Vpp must be 13V or higher.

It had become ridiculous that some users were advising others that a 10" cable is too long and will not work. They also proposed cable length of 6" or less. This was measured from the printer port to the programmer or from the programmer to the target PIC.

The experiment I did was to use 1 meter connecting wires and low Vpp voltage of 12V to show that both claims were not necessarily true.

Of course it is not reliable but most PIC programmers doesn't work had inherent hardware problems and long cable is the least worry of them.

Microchip defined the 6 inch cable for ICD2 to cover all family of PICS.
The ICD2 ICSP hardware driver seems to be too weak for some PIC chips.

One friend in ITALY just got this issue yesterday, and he fixed the issue by using a shorter cable.

 

[3v0]

Microchip defined the 6 inch cable for ICD2 to cover all family of PICS.
The ICD2 ICSP hardware driver seems to be too weak for some PIC chips.

One friend in ITALY just got this issue yesterday, and he fixed the issue by using a shorter cable.

Everything I have read talks mostly about reflections and to a lesser extent crosstalk. Both of these problems are lessened by a shorter cable. If you found info on drive problems I would like to read or hear more about it. The topic has me interested.

 

[binzer]

long icsp cable

Everything I have read talks mostly about reflections and to a lesser extent crosstalk. Both of these problems are lessened by a shorter cable. If you found info on drive problems I would like to read or hear more about it. The topic has me interested.

How about twisted pairs (like cat5) and tie the grounds together and terminate on one end (widely used practice)..