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Forum Index : Microcontroller and PC projects : Proposal for correct IDC I/O pin numbers.
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donmck Guru  Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Proposal for correct IDC I/O pin numbers. Having found the I/O connector on the back of the Maximite is incorrect because of a Component Overlay Error in Geoff's CAD program, I am proposing to change the signal names at the back of the case, so that they are correct to the outside world. Three or four of us have just spent hours (if not days) going around in circles over this, and I feel the best course of action is to make this simple correction now, so that any design engineers can follow it easily in the future. We are not changing anything inside the box. Not Geoff's schematic, or his pin numbers. What we are doing is converting to the correct pin numbers when the I/O leaves the back of the box, or board, and goes out via the 26 pin IDC connector. So we leave the schematic as being correct inside the box to Geoff's pin numbers. And as soon as it gets outside the box, it becomes standard pin numbers, OK? Very much like RX and TX have to change names at some point. This will mean that on the IDC connectors, where wire 1 is generally a red wire, it will in fact be a red wire. It will mean that the little arrow on the header that signifies pin 1, will actually be pin 1. It will mean that the square pad on printed circuit board design that signifies pin 1, will actually be pin 1. Rohan, as you are the only other person involved in I/O hardware design with the Maximite at this stage, I would appreciate your comments. In fact comments from anyone and everyone are very welcome. I am showing a small picture in this thread: 
and linking to a larger picture that you should be able to manipulate and print out in A4 size. http://www.themaximitecomputer.com/graphics/io-correction-bi g.jpg Again it is hand scribbled. If the standard is accepted, then we will produce a nicer looking look up table, and the Maximite world will be a better place. Cheers Don... https://www.dontronics.com |
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stuarts Senior Member  Joined: 15/06/2011 Location: AustraliaPosts: 199 |
Amen Don. Stuart Time is nature's way of keeping everything from happening all at once. |
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sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
thankyou don i gatjer the bottom one is correct you have two pictures here or am i a little con fused...but yes very greatful too many as i shure many would agree .... technicians do it with least resistance |
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| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
i know you have drawn this out but how does the pin conffiguireation match up withe i/o pins if i stpin(1) then what pin on the connector is that i/o please thankyou technicians do it with least resistance |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
In the hand drawn table I did in the previous message, the top one is Geoff's current pin-out looking into the back of the box. Same signals, but a different pin out in the bottom one. The bottom one conforms to normal design so that pin 1 is shown as a square pad, and this is what you will see Industry wide. I took this shot earlier tonight of one of my Olimex boards. It shows 2 R/A male headers, and 1 straight male header. If you look close, you will see pins 1 & 2 on all 3 connectors. You will also see the cut out on the R/A version. So pin 1 is the opposite corner of the connector to what it should be. 
Cheers Don... https://www.dontronics.com |
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| rhamer Senior Member Joined: 06/06/2011 Location: AustraliaPosts: 174 |
Yes I agree, and this is what I have done on my boards. So just to be clear, the pinouts as shown on the schematic are correct. The PCB numbering is correct. It's just the way the connector is loaded that is incorrect. So the answer on any new Maximite board is to rotate the connector footprint on the board (keeping the same connections) then the right angle connector can be fitted the right way around. Cheers Rohan Rohan Hamer HAMFIELD Software & Hardware Solutions Makers of the Maximite Expander. http://www.hamfield.com.au |
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| rhamer Senior Member Joined: 06/06/2011 Location: AustraliaPosts: 174 |
Actually looking at your diagram again, I'm now not sure. My view, and what I have done, is to throw away the RA connector, fit a straight one the right way round, then all is as it should be. If you really want to fit a RA connector to the original Maximite, then cut a new notch on the opposite side of the shell. If it is a new Maximite PCB then take the opportunity to rotate the footprint so any connector will work. If you just go with the reversed connector and then call it correct from this point on, it will always be wrong with respect to the circuit diagram. I'm also afraid that I am too far into my boards to change them now. Regards Rohan Rohan Hamer HAMFIELD Software & Hardware Solutions Makers of the Maximite Expander. http://www.hamfield.com.au |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
I can understand your last point Rohan, and I couldn't see you doing it any other way. I would have to do the same. But I keep going around in circles also, and I'm not sure either. My first board is basically a converter board from Maximite to the Arduino bus, and the connections will be correct. The only thing that will be odd is the pin numbers on the IDC connectors (I have four of them) and the Pin 1 orientation as far as anybody else outside of Maximite is concerned. People in the hardware game will spot that the pin 1's are all in the wrong spot. It would be nice to get a consensus of opinion on it and take a vote, and all of that jazz, but we want it last week, not next month. Perhaps I'll toss a penny in the air. Perhaps we........ Like Steve Buscemi in the Armageddon movie. "We staying, we going, we staying, we going?" I may leave it in the too hard basket. Like all these things, at least we kicked it around, found out the flaws, and the reasons why. Cheers Don... https://www.dontronics.com |
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jebz Regular Member  Joined: 13/06/2011 Location: AustraliaPosts: 79 |
Has anyone thought of removing the pins from the shell and re-assembling it the correct way round? . |
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VK6MRG Guru Joined: 08/06/2011 Location: AustraliaPosts: 347 |
Sounds like the simple things in life are often the best. Maybe the simplest solution. Its easier to ask forgiveness than to seek permission! ............VK6MRG.............VK3MGR............ |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
It isn't a mechanical thing, it is simply pin assignment. And it is a molded fitting, so it can't be changed, but thanks for the suggestion. An analogy: The firing order of a four cylinder car is normally given with no# 1 being the front cylinder. The firing order may be 1,4,3,2, but if cylinder 4 is incorrectly called cylinder 1, then the chart for the firing order is wrong, and mechanics will have trouble getting the thing to fire until they are told, that cylinder No# 1 is the one nearest the driver, and not the one at the front of the car near the radiator, just like every other 4 cylinder car on the road. Did I pass Mick? Cheers Don... https://www.dontronics.com |
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| jebz Regular Member Joined: 13/06/2011 Location: AustraliaPosts: 79 |
I removed a pin from an IDE 40pin connector identical to these when someone jammed the cable with a blocked hole onto a drive back the front similar to this. It was easier to do a pin swap than remove the whole connector assembly from 2 drives then re-assemble the repaired drive. |
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| rhamer Senior Member Joined: 06/06/2011 Location: AustraliaPosts: 174 |
Yeah, I thought of that, and I think it is quite possible. I stopped short of recommending that to my customers as I have to allow for various skill levels. It's one of those things that is annoying, and not easily solved. But I still maintain, that if you throw away th RA connector, all the problems go away. Regards Rohan Rohan Hamer HAMFIELD Software & Hardware Solutions Makers of the Maximite Expander. http://www.hamfield.com.au |
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| VK6MRG Guru Joined: 08/06/2011 Location: AustraliaPosts: 347 |
Is it as simple as mounting the right angle connector to the under side of the PCB and not the top? Its easier to ask forgiveness than to seek permission! ............VK6MRG.............VK3MGR............ |
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| stuarts Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 199 |
I think the fact that the maximite exists in what I presume are many hundreds or thousands based on the altronics backorders. What we have is what we have. Almost all of them are going to have the right angle connector installed on them. I think the best thing that could be done would be to redraw the schematic with the right pin numbers and then make sure that the connector is oriented correctly in the board layout. What it means is that there is no need to change any physical hardware. Effectively what Rohan has told his customers is solder the straight connector on backwards. This means that his boards are only compatible with maximites with the straight connectors on backwards, not the standard one with the right angle connector. In reality, we could all right new pin numbers on our schematics and make the schematic correct, copy the same numbers to the pin layout in the Maximite user manual and all will be right. Stuart Time is nature's way of keeping everything from happening all at once. |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Yes. That would also correct it all. But........... You would end up with a R/A connector under your board, instead of on top, which has the obvious draw backs, however it would look like a duck, and quack like a duck, in fact, it becomes a permanent submarine duck. Wild Geese, Headless Chickens, Submarine Ducks. Aviary Birds in Australia by Max and Mite. $9.95 from all good book shops. Available on Kindle from Amazon, and soon to be released for all eReader platforms. Cheers Don... https://www.dontronics.com |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Stuart's 4th of July message for all Maxiteers. A statement that will go down in history, as I know he is right, and explained it very well. I push, I get answers. I still need answers to the Arduino power rails, but I think I have that in another thread, and will go in that direction. Now where did that thread go? Now who is going to tell Mick to change all his footprints, to say nothing of his net list? Cheers Don... https://www.dontronics.com |
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bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
NO It would NOT correct it you would have pin 1 in pin 25 position not pin 26. Sorry Mik Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
No doubt about Mick. :-) I pay him peanuts, and get a guru. Something terribly wrong here. No submarine duck? Better a lame duck, than out for a golden duck, or not having a bash at it. I hate it when that happens. I thought I said duck. If you say nothing, you will never make a mistake. For international consumption: http://en.wikipedia.org/wiki/Duck_%28cricket%29 Cheers Don... https://www.dontronics.com |
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| rhamer Senior Member Joined: 06/06/2011 Location: AustraliaPosts: 174 |
That is most certainly not correct. I have told them to solder a straight connector on the correct way pin for pin. You seem to be missing the point, it is the use of a right angle connector that causes the problem, nothing else. The circuit and the board match. If you fit a right angle connector correctly it matches too but faces inward, not outward. You should be correcting the original error not compounding it by making another correction. Remember this is a hobbiest device and not a sealed appliance, people will always want to refer to the circuit for some special modification. Regards Rohan Rohan Hamer HAMFIELD Software & Hardware Solutions Makers of the Maximite Expander. http://www.hamfield.com.au |
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