[Lf] [Fwd: LF: DDS Board "Engineering model" works perfectly.]

[Andre' Kesteloot]

Andy Talbot wrote:

> To all interested in the DDS module.
> (Larry could you pass on to others who don't monitor the LF reflector
> please)
>
> I've had a proper artwork made and produced a couple of PCBs at home for the
> AD9850 DDS module.  Results with the home produced board aren't perfect as
> my PCB material is quite old now, and UV exposure is a bit uncertain, but
> one board is quite acceptable and the other just had to have a few whiskers
> cleaned off with a hot iron.
>
> Today I've just assembled one board with a spare AD9850, and it works
> perfectly as expected.  What's more,  that is after having to remove the IC
> and replace it as I had carelessly trapped a tiny bit of solder which was
> shorting two tracks under the chip (fortunately non fatal) and probably due
> to the home produced PCB.  Certainly don't recommend that procedure !!!
>
> I'll get in touch with the PCB manufacturer we've used before and get a
> quote for 100 off.   Should be reasonable if we don't put a tight timescale
> on the job - say 3 - 4 weeks so the company can batch them with other jobs.
> Meanwhile I'll do an initial write up and send that to all who have
> contacted me directly so far (about 20).
>
> To those who aren't familiar with the story so far :
>
> This DDS module is a small PCB containing an AD9850 Direct Digital
> Synthesizer with output filter and PIC controller chip.  It is intended as a
> drop in module for other projects rather than a stand alone pice of
> equipment as are the QEX and G0MRF etc designs.   For simple single
> frequency programming an ASCII terminal is all that is required, but the
> real aim was to provide a straightforward command set so that anyone can
> write their own driver programmes without having to worry about the
> intricacies of addressing the 9850 itself.
>
> It requires a clock source (0 - 5V level) at any frequency from DC to 120MHz
> and  interfaces with a PC via the serial RS232 link.  The PC is used to set
> frequency information and phase key the output using commands based on
> simple text characters, frequency is stored in non volatile memory for
> instant single frequency start up.   The PIC software is written, but there
> may still be a bit of fine tuning (no pun) that can be done on it yet while
> waiting for the proper PCBs.  One option that I'm not sure whether to add or
> not,  is the option of using the one PIC to control a second DDS as well,
> with an additional set of commands.  This would be mounted on a second PCB,
> but without its own PIC, and interface to the controller using some of the
> spare control lines.
>
>  We haven't fully decided what to supply just yet - the PCB alone, with the
> 9850 chip, a programmed PIC etc etc.  Price is still to be fixed depending
> on interest shown (and projected) and how much money we decide to put up
> front in bulk purchasing.  At some later time - a fully assembled module MAY
> be available, but that depends on demand.  Looking at replies received so
> far, whilst a few would like a fully assembled unit, many would be happy
> with just a PCB.
>
> Andy  G4JNT
>
> mailto:ACTALBOT at DERA.GOV.UK     During the working day   or  G4JNT at ARRL.NET
> at other times