Sort of Gray code to binary converter

Well so far we've got quite a plethora of answers. Ken seems to be ahead of the field in the hardware stakes, although he's keeping the design under wraps just now ;-). I like the 16V8 or 22V10 PLD approach and that could yet creep to the front of the field.

The software field is more open. Several people had suggested a PIC, that's definitely not in the field as the hardware is tooo.. ugly! Now an AVR, yes that's a goer, but not in assembler as that is ugly as well. So we're probably looking at 'C' on an AVR as the front runner. Look-up tables are too wasteful and if(); else if() or switch{} contructs are too ugly so let's have some lateral thinking.

It's interesting to see that Win is keeping his powder dry. As one of the perpetrators of my long time reference book of 20 odd years standing I would like to know what he's thinking.

Anyway there's still nine days left until the Northern Hemisphere Winter Solstice (that's for the pedants) and, as long as we can keep the momentum up, the competition closes three days after that.

It looks as though there will have to be two toasts drunk as a celebration. I'll need to get out my zimmer frame to be able to stand up after that.

Happy thinking.

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John B

In article , snipped-for-privacy@yahoo.com wrote: [... me ...]

In ASM you can do like this:

Table: rept 256 ; Repeat 256 times db 0FFH ; Fill with error endm ; End repeat

org Table+00000011 ; Address the cell db 1 ; Put the value in org Table+00000110 db 2 .... etc ....... org Table + 256 ; put the pointer to after the table ... more code ...

As is often the case, it is easier to do in ASM.

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kensmith@rahul.net   forging knowledge

A PIC has a really huge number of gates inside. Personally, I'd more likely put it into a CMOS 22V10. Both you and my practical solutions contain more logic than the ones we are comparing.

A real contest would be to do it in terms of transistors.

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kensmith@rahul.net   forging knowledge

In article , John Larkin wrote: [...]

Yes. Get one of the "zero power" ones and you can run it for a couple of years on a 9V battery.

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kensmith@rahul.net   forging knowledge

Actually, no it isn't under wraps. The only thing I didn't say was the obvious. Take a look at my first post on the subject where I said that it takes a priority decoder+parity generator+quad nand. I gave what each does.

This would be my vote.

Anything involving "C" makes me ill.

If the chip you use has the code space needed, you may as well go that way. You can't save the unused part of the prom for use in some future chip.

If your CPU does floating point with the IEEE format:

Assume that EXP returns the exponent part of the number. Assume that MAN returns the mantissa part of the number without the implied bit.

if ( X == 0x81) Y = SOMEVALUE else { TempFloat = X Y = (2 * EXP(TempFloat)) + ( 1 & (0 < MAN(TempFloat))); }

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kensmith@rahul.net   forging knowledge

The decode boils down to two groups of 4-bits and that can be done with a single dual quad-input mux for 4 data I and one mux select output O. Most u's should have a count ones instruction so jump out on error for sum >2 on both nibbles or 0 on both. From that point he has a simple

4-bit decode which is 1/16 the loading of a full 8-bit decode. This reduces complexity in the same way as a matrix decoder reduces an MxN decode into an M+N burden.

As it stands, the contest is not well-defined. I mentioned the PIC solution not as a solution to the contest, but what I would use if I just had to do the job.

But I haven't seen any other claim of a solution with the 27 gates in my solution:

-Robert Scott Ypsilanti, Michigan

snipped-for-privacy@green.rahul.net

snipped-for-privacy@green.rahul.net

chips.

of

place

more

solutions

Spare parts from a Friedan mechanical calculator....

With ABEL locked up in Xilinx' hands (even if still available in Foundation and WebPak, with fitters for their parts), we're having to once again consider CUPL. For example, Atmel's venerable V750 and V2500. Both were favorites of mine for their logical power and for their low power, :-), and were upgraded a few years ago to the ATF750CL and ATF2500C series (still available in DIP, yeah!). These are attractive parts that demand the use of Atmel's free CUPL.

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 Thanks,
    - Win

I still use the Gould AMI/ICT "Peel" software to program 18CV8's and

22CV10's. It's an old dawg dos thing, still works fine.

John

[snip...snip...]

Atmel's free-for-download WinCUPL. (Very) occasionally VHDL but somehow the CUPL syntax "feels better" for those very small devices.

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Rich Webb   Norfolk, VA

[snip...snip...]

Good thread.

One thing to keep in mind is that exporting the conversion to an off-board device, like a GAL, loses the benefit of having only one bit change per sector transition. I'd be awfully tempted to keep the eight data lines separate until they reached the data logger/display. Otherwise, consider adding a data-valid pulse (with the accompanying need for setup and hold times) or do the tell-me-three-times routine.

Alternately, sample all the parameters at the sensor head (including, perhaps, wind speed, temperature, humidity, ...) and squirt the whole data packet as a serial bitstream.

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Rich Webb   Norfolk, VA

On 12/12/2005 the venerable Rich Webb etched in runes:

I've actually got a real copy of Logical Devices' WinCupl 5.0. I think they went to the wall a few years ago. WinCupl's a bit flaky but does cope with the 26V12 which I used to use a lot. The Atmel free version is only CUPL 4 and doesn't stretch to the 26V12. That's probably because only AMD and Lattice ever made them.

There's also ispLEVER which is a free download from Lattice

It's *big* and not so easy to use as CUPL.

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John B

In article , Spehro Pefhany wrote: [...]

I have a program from ICT called Place. This is a MS-DOS program. Of all the programs for doing a 22V10, it is by far the best.

It has a semi-GUI for clicking the various options on the macro-cell configuration. The langage is very much like ABEL for entering the equations.

Unfortunately two bad things have happened. ICT sold off their SPLD stuff to Anachip and they did a poor job of porting Place to windows.

ICT had some very nice stuff. They made a thing like a 22V22 where all of the pins had macro-cells connected to them. They also let you shift the flip-flop to latching the input. This all fit in the space of a normal

22V10.

If the input lines have any drive, you can do this:

One Bit ------------ ! !!- Another bit ------!!- N-MOS !!-----------------To diode array

--- If the inputs swing 5V can get the LSB like this ---

\\ / \\ 10K 10K / R-pack ! HC04 -/\\/\\-- +--!>o---- -/\\/\\--+ !/ -/\\/\\--+----+------! Si NPN eg: 2N2222 5 more ! !\\e resistors / ! \\ GND / \\ 3.32K ! GND

5/11 = 0.455 Safely off 2*5/11 = 0.91 On enough

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kensmith@rahul.net   forging knowledge

In article , Rich Webb wrote: [...]

You can make it tell you on demand with very little hardware. You send a character like 55H to it and it uses the edges to clock the bits back to you. S 0 1 2 3 4 5 6 7 -- -- -- -- --

---- -- -- -- -- -------

You need some oneshotting to reset the state between characters.

State.R = SomeRC; State.CLK = !Sin; ... stuff ...

Sout = Sin # ( Bit0 & (State == 1) #Bit1 & (State == 2) #Bit2 & (State == 3) #Bit3 & (State == 4));

... more stuff ...

Since you already needed to tranlate codes, this doesn't add much to the software task.

If yor really want a complex Mickey-Mouse system, you can use the recieving of 00H to reset the state and put in a lot more states to send a lot more bits. An modest CPLD can MUX a lot of data onto a serial port this way.

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kensmith@rahul.net   forging knowledge

Good grief, what an instruction set! How do you pronounce "btfsc" or "xorlw"?

John

The midrange PIC doesn't have a compare instruction, but there's a trick where you XOR a literal based on the previous set of XORs to give zero when you get the desired match.

Eg.

; input port in w, return result in w, 0xFF for invalid input convert: xorlw 0x01 btfsc STATUS,Z retlw 0x00 xorlw (0x3 ^ 0x01) btfsc STATUS,Z retlw 0x01 xorlw (0x2 ^ 0x03) ... xorlw (0x81 ^ 080) btfsc STATUS,Z retlw 0x0F retlw 0xFF

Should run in 55 or 60 microseconds port-to-port in a 4MHz PIC running of the internal 4MHz RC (no external parts).

Or use an FPGA with a few lines of HDL and get ~10ns pin-to-pin for those fast-changing wind directions. ;-)

Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

It's really just a PDP-8.

John

It's a 1-chip and 2/3 component solution.

An 18-pin PIC gives the required 8+4 i/o, plus either a 3-pin ceramic resonator, or running in RC mode. A simple linear 16x comparings code would probably be less than 100 instructions.

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Tony Williams.