Raghunathan wrote:

Though you make it sound easy, I am sure it must have taken quite a bit of time to make the layouts and post them with your comments.

Hans wrote:

Despite the effort that Kai has put in, and the nice layout he produced he has in fact exactly not demonstrated what he states, and that is how easy it is to do this! What it demonstrates is that in the hands of somebody who knows what he is doing and equipped with a lot of knowledge and experience, YES, it is easy. But to starters like Paul it isn't. Kai didn't you start small too?

Rob wrote:

If Kai had not used a shortcut when laying out the address lines, Paul could have slightly modified the circuit to accept a standard eprom in /EA fashion (and Kai has put a jumper for this).


Hallo guys,

I'm sorry, I didn't want to discourage Paul. And I didn't want to make a talebearing. Not at all. Just the opposite. Ok, it's my job to make layouts nearly every day. And it's not my first layout arround 80C52 in combination with this '573 latch and CMOS RAM. So, it really took this little time to make this layout.

I appologize for not telling that I scrambled addressbus. But it was never the plan to make a ready solution. The schematic Paul gave is incomplete anyway. There are signals which go to nowhere. It seems, that this schematic is only part of a bigger system. At least, there should be some small programmer circuitry and a special socket for EPROM on an extra print, I guess.

I only wanted to demonstrate, how copper traces should be routed. Where to put decoupling capacitors, how to provide the PCB with a solid ground plane, etc. From the 'detailed view' picture he could have seen how big to create solder points, how thin to create signal traces, etc. That was the intention. And if Paul would have come back there would have been a certain probability that I would have helped him to route the whole print.

Hans, you asked me, whether I didn't start small, too. Well, I started so small, you cannot imagine. When I started with electronics, personal computer was out of reach of anyone. There was no free shareware PCB layout program in net. All has to be painted directly on PCB with 'DALO 2M professional', if someone remembers. To paint 8+16 buses was nearly impossible with this technique, and double-sided PCB was the hell. After all this painting which took many many hours, etching in FeCl very often resulted in total ruin, because the painting was suddenly disappearing.
There was also an era, where I fabricated the signal traces with very thin wires. But the work was even more unsatisfying.
I remember, that some people used adhesive tapes and 'glued' the whole circuit directly on transparent foil. But to get a PCB from it from a PCB manufacturer was nearly out of reach of an amateur, because costs for one prototype PCB were astronomically.

All these problems do today beginners NOT have! The PCB layout program I work with (target) is available as light-version, costing only some euros. With this cheap program you can work like a professional, unless your board is getting too big. You can use automatic massplane generation, have access to hundred different layers, can use fabricated symbols, etc. etc. etc. Compared to former times, today it's really much easier to get a PCB. You don't have to fizzle arround with bread boards and other stuff. And if your PCB layout is ready you just contact 'pcb-pool' company, mail your file, and get a double-sided PCB, with vias, solder stop laque, etc. for less than 50 dollars!

So, why should a beginner NOT use possibility of self-fabricating PCB? Mostly, they follow a ready concept, follow a book or something else, where even a ready layout is published. The only thing they have to do is to copy it.



May be I offend someone, but I'm strictly against to encourage an absolute beginner, that he will be able to fabricate a microcontroller circuit on a bread board! The resulting failure is much more discouraging, than to tell him, that he will need a proper fabricated PCB. I know very well, what I'm talking about. I suffered from this shitty stuff so many times...

Also, what when his 'LED-blinking phase' is over, when he wants to build something more interesting? Shall he also build this with bread boards? What, when he wants to switch from oldfashioned 8052AH to a modern microcontroller, which will automatically be a faster one? Still build with bread board? What when he needs FAST-TTL or 74ACMOS-chips? Still bread board? Why shall he begin with something which is absolutely inappropriate, unless he builds the most simple circuit?

No, when working with microcontrollers some rules have to be obeyed. And this a beginner must learn from the first day on. Microcontrollers need a proper fabricated PCB. This is especially valid, when circuits contain extended bus structures! A solid ground plane should be introduced whenever possible, or at least as wide as possible copper traces for ground routing, which results in an inductivity, which is much smaller than any bread board design. (One of my last replies dealt with this inductivity issue.)

I know, that many people are now thinking, that in former times there were many circuits arround not containing solid ground plane, making crossings everywhere on the PCB. Well, these circuits didn't contain modern microntrollers and modern digital chips like 74HCTMOS. They contained 'slow' microprocessors and 'friendly' 74LS-TTL. That's something totally different. But things have changed, what was fine in former times isn't fine today. Why do so many people (also from this forum) contact me and tell me that they have problems with their new PCB? Why is there growing a whole industry, providing help against problems arround the PCB, providing hardware debugging tools, helping to improve layouts and helping to pass through CE testing? Because it's so easy to build a circuit on a bread board, or by wire-wrapping or something else? Shurely not! But because so many people neglect to obey these valid design rules. Because they neglect the concept of solid ground plane, e.g.
A beginner cannot learn early enough, that connections on a PCB between two fast digital chips are far away from what is achievable by a simple piece of wire, but form a transmissionline in combination with the solid ground plane directly underneath signal trace. He should learn, that connections between chips use a different technique than what is used with low frequency electronics. So, that he automatically gets a bad feeling, everytime when he interrupts solid ground plane underneath bus lines.

And because microcontrollers become faster and faster almost every day, use of concept of solid ground plane becomes more and more demanding. Not the right moment to encourage a beginner to start with a bread board. Instead, he should learn from begin on to fabricate his own PCB. That's my individual point of view.

Kai