> -----Original Message----- > From: time-nuts-bounces@febo.com > [mailto:time-nuts-bounces@febo.com] On Behalf Of David C. Partridge > Sent: Monday, June 02, 2008 1:20 PM > To: 'Discussion of precise time and frequency measurement' > Subject: [time-nuts] PCB design questions > > I've been working on the design for a frequency divider to > complement the Thunderbolt I recently bought from TVB (thank > you Tom, it's working very well as far as I can tell, though > of course I've no other standard to compare against). > Dave, I just made one using a single microcontroller chip soldered on a Toolstick from Silabs. The Toolstick is a small PWB with a small 8051 class microcontroller in surface mount package. The Toolstick costs $10 and you need a $18 programmer to flash it. I run the uC using the 10 MHz as external clock and it has (for now) a 1Hz output. The toolstick I used is similar to the one described on this page: http://www.ko4bb.com/Test_Equipment/AFSignalGenerator/SigGen.php The software is just a couple of for() loops to kill time, a few 2 and 3 cycles instructions to adjust the timing perfectly (cannot do NOP from C with the free compiler, but you can program in assembly if you need to feel some pain) and one output is twiddled at the right time. The processor is using the 10 MHz as clock. A single chip is all that is required, the chip I actually used is a C8051F530-IT, which costs about $4 on the Silabs web site (qty 1) and comes in a 20 pin TSSOP package (surface mount, but solderable by hand). You really only need to connect 4 pins for that job, supply voltage and ground, 10 MHz input and 1Hz output. Silabs has a couple of parts that are available in DIP package, notably the C8051F330D (refered to as the 330-GP) which is roughly the same core as the 530. If you buy the bare chip, you will have to buy the programmer separately, so if you just want to build a few simple projects, you are better off buying the toolsticks. You might want to add a D flip-flop to clean up the edge, even though I do not know the jitter of the chip itself (I have planned to test it as well as I can, but there are more projects in the pipe at the moment than time to address them) I am working on a version with both 1 kHz and 1 Hz outputs. There are a few sine-to-square converters (clock shapers) on Bruce's page at http://www.ko4bb.com/~bruce/ Didier KO4BB Internal Virus Database is out-of-date. Checked by AVG. Version: 7.5.519 / Virus Database: 269.23.11/1422 - Release Date: 5/8/2008 5:24 PM

At 06:05 PM 6/2/2008, you wrote: >Bob Paddock wrote: > > >>> 2. How many layers? In an ideal world with money no object, if I > >>> understand the current art correctly, I think I'd probably aim for a five > >>> layer > > > > I assume that is a typo? You can not have an odd number of layers. > > In this current 3D reality each layer has two sides. :-) > > >Sure you can. I have done 3 layer, 5 layer, and 7 layer boards. > >Having done those, I will advise you not to do 3 layer, it warps. But >everything else is easily do able. ><snip> >6 layer can be made by: > >2 side | 0 side | 2 side | 0 side | 2 side >... > >The only down side to odd numbers of layers is the supply house >has to stock 1 sided laminate. or etch ALL the copper off one side of two sided.. Jim

On Monday 02 June 2008 02:19:52 pm David C. Partridge wrote: > I'm now thinking ahead to the PCB requirement... http://focus.ti.com/lit/an/scaa082/scaa082.pdf http://www.ti.com/litv/pdf/scaa082 "Application Notes Abstract High Speed Layout Guidelines This application report addresses high-speed signals such as clock signals and their routing and gives designers a review of the important coherences. With some simple rules, electromagnetic interference problems can be minimized without using complicated forumulas and expensive simulation tools. Section 1 gives a short introduction to theory, section 2 focuses on practical PCB design rules. Either section can be read independently." -- http://www.wearablesmartsensors.com/ http://www.softwaresafety.net/ http://www.designer-iii.com/ http://www.unusualresearch.com/

A most helpful document - many thanks for the pointer. Dave -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Bob Paddock Sent: 06 June 2008 02:17 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] PCB design questions http://focus.ti.com/lit/an/scaa082/scaa082.pdf