[time-nuts] FE-5680A Mechanical Question

shalimr9 at gmail.com shalimr9 at gmail.com
Sat Jan 14 14:22:42 EST 2012

Silabs has a uC, I think it is the C8051F350 but I may be wrong, that has a 24 bit ADC with 1-128 gain PGA and offset DAC (and two 8 bit DACs).

Most their chips are available already soldered to a small development board called Toolstick that typically costs $10. You will also need a $20 base Adapter (the USB programmer/debugger)

You can use the demo Keil compiler, but it is severely crippled, so instead I recommend the free SDCC.

Silabs has lots of sample software for their chips, and an excellent (free) IDE/debugger that supports Keil, SDCC and other compilers.

I do have an article on the wiki on my web site about it www.ko4bb.com

I also have a page about a simple audio generator using an 8051 as DDS on my web site that describes the tools I use and how to configure the IDE for SDCC.

Didier KO4BB

Sent from my BlackBerry Wireless thingy while I do other things...

-----Original Message-----
From: Jim Lux <jimlux at earthlink.net>
Sender: time-nuts-bounces at febo.com
Date: Fri, 13 Jan 2012 08:37:13 
To: <time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] FE-5680A Mechanical Question

On 1/13/12 8:15 AM, Chris Albertson wrote:
> On Fri, Jan 13, 2012 at 3:19 AM,<EWKehren at aol.com>  wrote:
>> What we know is that you can set the Rb in 7 E-13. Dithering would allow
>> even closer setting, the question is what rate will the Rb accept with out
>> loosing lock or deterioration of the performance. Some one should explore
>> that.  I am still waiting to se some aging. Taking the 10 MHz output and than
>> use an  analog loop and something like a Morion OCXO and you have the best of
>> all.
>> Digitally controlling the Rb will cut the cost of the control loop in half.
>>   For $10 in parts and a PC board for less than $10 using Shera like
>> controller  can be realized. What is needed is some one able to do the PIC.
>> If some one is interested and able, please contact me off list. A low cost
>> GPS or a 1 pps output of a Tbolt be perfect source.
>> Bert Kehren
> Don't use a PIC for the prototype.  A desktop PC could work as well
> and everyone here already has one.   Connect the FE5680 to the PC's
> serial port and send commands to adjust it.  The PC also needs to be
> able to read a voltage.   Many already have audio input with 24-bit
> ADC chips.

But those audio inputs are almost always AC coupled.

Bringing up a question: Does anyone know of a cheap (<$20ish) USB 
voltage sensor (16 bits or better, ideally)..  I can see one of those 
Atmel USB capable micros (like the one on the Arduino Uno) hooked to a 
dual slope or successive approximation ADC.

There seem to be an amazing number of times that I want something like 
that.  The DATAQ $29 widget is only 10 bits, unfortunately.  A USB 
interface DMM would work nicely, but I haven't found one that's in the 
under $50 price range.

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