Looking for simple way to interface BCD to serial (RS232)

(I repeat)

The device I am talking about is a Doppler Systems DDF4002 doppler direction finder. It is an older modele that once had a serial interface option which is no longer available.

Your observation about the update rate is quite correct and is covered in the manual for the DDF4002, The theory section of the manual describes almost exactly the data rate assumptions you have stated but qualifies it with:

"However, the message is initiated only when the display is updated. Since this occurs at a maximum rate of 1/1.875 (0.533) seconds, ample time exists between characters and between messages to prevent overrunning.

There is also a later hardware mod to raise the 16X clock (4800 Hz from main board) to 38,400 Hz to provide 2400 baud.

As you have the schematic why not use the solution provided there? Or is this part left out? But even then you'd find some remnants of the interface that'll make it much easier to provide a solution.

Supposing you have a signal that initiates the display update (and there must be some) the next algorithm will due (either in hardware or in a micro):

1. Wait for display update
2. Wait for leading edge of address pin 1
3. Load digit 1 in shift register and shift it out
4. Wait for leading edge of address pin 2
5. Load digit 2 in shift register and shift it out
6. Wait for leading edge of address pin 3
7. Load digit 3 in shift register and shift it out
8. Goto 1

If you really want a hardware only solution, the schematics of John Fields will give you a headstart.

petrus bitbyter

OOps??

We already shipped 100,000 units based on your last post!!

-- Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com

------------------------------------------------------------------ There are only 10 kinds of people in this world, those who understand binary and those who don't.

They wouldn't have made them out of the test department if you were running a good shop. So you should have said "we just scrapped 100,000 units..."

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Which immediatly leads to the next question, what is on the other side of= that chip?

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rate.

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Seeing as this your first post in this thread i have found, perhaps your=20 post did not appear in much of Usenet. =20

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productive.

Interesting. Your previous post reached OP but not me. I already know=20 that my news host does not get/propagate all posts.

chip?

chip?

An analog input signal :-)

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of that chip?

Already having the data in a convenient form reduces the design = complexity.

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of that chip?

And that would lead to an entirely different solution space.

that chip?

that chip?

that chip?

Certainly. A different problem space, of course, has a different solution space. ;-)

Your (first) solution was clearly the simplest, given that an appropriate baud rate generator can be had easily.

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side of that chip?

That's odd. I was under the impression that the output of the 7217 was=20

that chip?

It actually has both 7 segment drivers and BCD I/O's. The lines used to strobe the display segments also used to address the BCD output.

"JosephKK"

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side of that chip?

which

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solutions

Looked up most probable chip. Weird. But i more nearly understand now.